Natural phenol
Encyclopedia
Natural phenols, bioavailable phenols, plant phenolics, low molecular weight phenols or phenoloids are a class of natural product
s. They are small molecules containing one or more phenol
ic group. These molecules are smaller in size than polyphenol
s, containing less than 12 phenolic groups. They can be classified as simple phenols (monophenols), with only one phenolic group, or di- (bi-), tri- and oligophenols, with two, three or several phenolic groups respectively. They can be found in plants and have an antioxidant activity. They are the most widely distributed class of plant secondary metabolite
s and several thousand different compounds have been identified.
comes from Petunia
or the name viniferin
comes from Vitis vinifera
.
s) have two, and pyrogallol- and phloroglucinol-types (benzenetriol
s) have three. Natural phenols may have heteroatom substituents other than hydroxyl groups; as might be expected, ether and ester linkages are common, as are various carboxylic acid derivatives.
Natural phenol compositions are normally limited to carbon
, hydrogen
and oxygen
in undefined proportion. As a class, they do not contain nitrogen
, element characteristic of amino-acids (see tyrosine
and L-DOPA), catecholamine
hormones or alkaloid
s.
Natural phenols spectral data show a typical UV
absorbance characteristic of benzene aromaticity at 270 nm. However, according to Woodward's rules
, bathochromic shift
s often happen suggesting the presence of delocalised π electrons arising from a conjugation between the benzene and vinyl
s groups.
Many natural phenols present chirality
within their molecule. An example of such molecules is catechin
. Cavicularin
is a unusual macrocycle because it was the first compound isolated from nature displaying optical activity due to the presence of planar chirality
and axial chirality
.
Natural phenols chemically interact with many other substances. Stacking
, a chemical property of molecules with aromaticity, is seen occurring between phenolic molecules. When studied in mass spectrometry, phenols easily form adduct ions with halogens. They can also interact with the food matrices or with different forms of silica (mesoporous silica
, fumed silica
or silica-based sol gel
s).
The largest and best studied natural phenols are the flavonoid
s, which include several thousand compounds, among them the flavonols, flavones, flavan-3ol (catechins), flavanone
s, anthocyanidin
s and isoflavonoid
s.
The phenolic unit can be found dimerized or further polymerized, creating a new class of polyphenol. For example, ellagic acid
is a dimer of gallic acid and forms the class of ellagitannins, or a catechin
and a gallocatechin can combine to form the red compound theaflavin
, a process which also results in the large class of brown thearubigin
s in tea.
Two natural phenols from two different categories, for instance a flavonoid and a lignan, can combine to form a hybrid class like the flavonolignan
s.
et al., published in 1980:
and pyrocatechol
are found in Agaricus bisporus as well as other phenylated substances like phenylacetic
and phenylpyruvic acid
s. The hardening of the protein component of insect cuticle has been shown to be due to the tanning action of an agent produced by oxidation of a phenolic substance. In the analogous hardening of the cockroach ootheca
, the phenolic substance concerned is 3:4-dihydroxybenzoic acid (protocatechuic acid
).
Natural phenols can be involved in allelopathic
interactions in soil. Juglone
is an example of such a molecule inhibiting the growth of other plant species around walnut trees. The nodule formation in Medicago truncatula
is apparently dependent on the flavonoid
s pathway. Pterocarpan
s serve as phytoalexin
s in Trifolium pratense and other Fabaceae.
Furanocoumarin
s are phenolic and are non-toxic until activated by light. Furancoumarins block the transcription and repair of DNA. Therefore, they are considered phytotoxin
s.
Natural phenols can be enzymatically polymerised. Laccase
and peroxidase
induced the polymerization of syringic acid
to give a poly(1,4-phenylene oxide) bearing a carboxylic acid at one end and a phenolic hydroxyl group at the other.
In soils, it is assumed that larger amounts of phenols are released from decomposing plant litter
rather than from throughfall
in any natural plant community. In the soil, soluble phenols face four different fates. They might be degraded and mineralized as a carbon source by heterotrophic microorganisms; they can be transformed into insoluble and recalcitrant humic
substances by polymerization and condensation reactions (with the contribution of soil organisms); they might adsorb to clay minerals or form chelates with aluminium or iron ions; or they might remain in dissolved form, leached by percolating water, and finally leave the ecosystem as part of dissolved organic carbon (DOC).
Volatile phenolic compounds are found in plant resin
where they may attract benefactors such as parasitoid
s or predators of the herbivores that attack the plant.
s like karanjin
or rotenoid
s are used as acaricide or insecticide
.
pathway, malic acid
pathway or both. The aromatic amino acid phenylalanine
, synthesized in the shikimic-acid pathway, is the common precursor of phenol containing amino acids and phenolic compounds.
In plants, the phenolic units are ester
ified or methylated
. The polyphenols are submitted to conjugation. Many natural phenols are found in the glycoside
form instead of the aglycone
form.
In olive oil, tyrosol
forms esters with fatty acids. In rye, alkylresorcinols are phenolic lipids.
Some acetylations involve terpene
s like geraniol
. Those molecules are called meroterpenes (a chemical compound having a partial terpenoid structure).
Methylations can occur by the formation of an ether
bond on hydroxyl groups forming O-methylated polyphenols. In the case of the O-methylated flavone tangeritin
, all of the five hydroxyls are methylated, leaving no free hydroxyls of the phenol group. Methylations can also occur on directly on a carbon of the benzene ring like in the case of poriol
, a C-methylated flavonoid
.
In animals and humans, after ingestion, polyphenols become part of the xenobiotic metabolism
. In subsequent phase II reactions, these activated metabolites are conjugated with charged species such as glutathione
, sulfate
, glycine
or glucuronic acid
. These reactions are catalysed by a large group of broad-specificity transferases.
, tea
, beer
, olive oil
, chocolate
or cocoa
, coffee
, pomegranate
s, popcorn
, yerba mate
, fruit
s and fruit based drinks (including cider and wine) and vegetable
s. Herb
s and spice
s, nut
s (walnuts, peanut) and algae are also potentially significant for supplying certain natural phenols. Such food
s containing natural phenols are generally considered as health food
.
Natural phenols can also be found in fatty matrices like olive oil
. Cloudy olive oil
has the higher levels of phenols, or polar phenols that form a complex phenol-protein complex.
Phenolic compounds, when used in beverages, such as prune juice, have been shown to be helpful in the color and sensory components, such as alleviating bitterness.
and the European Food Safety Authority
(EFSA), dietary flavonoid
s have little or no direct antioxidant
food value following digestion. Not like controlled test tube conditions, the fate of natural phenols in vivo
shows they are poorly conserved (less than 5%), with most of what is absorbed existing as chemically-modified metabolites destined for rapid excretion.
Cinnamates have been shown to have more antioxidant activity when exposed in vitro to the Fenton reaction (catalytic Fe(II) with hydrogen peroxide) than the other natural phenols present in wine.
, antiviral
, anti-inflammatory
, and vasodilatory actions.
Epigallocatechin gallate
(EGCG), a flavanol found in tea, may have an effect on cancer by inhibiting DNA methyltransferase
activity. It has been shown to reduce reactive oxygen species
levels in vitro.
The natural phenol resveratrol
inhibits occurrence and/or growth of experimental tumor
s.
activate human SIRT1, extend the lifespan of budding yeast, Saccharomyces cerevisiae
, and may be sirtuin-activating compound
s. Other examples of such products are butein
, piceatannol
, isoliquiritigenin
, fisetin
, and quercetin
. Longevity
increased by resveratrol
was demonstrated in Caenorhabditis elegans
and Drosophila melanogaster
. This longevity increase may be due to a caloric restriction effect. Resveratrol
also increases the lifespan of vertebrates as has been demonstrated in short-lived fish, Nothobranchius furzeri
.
Other experiments on Drosophila melanogaster
indicate that natural phenols (gallic acid
, ferulic acid
, caffeic acid
, coumaric acid
, propyl gallate
, epicatechin, epigallocatechin, and epigallocatechin gallate
) may influence mechanisms related to Parkinson's disease
. Quercetin
and rutin
act against scopolamine
-induced memory impairment in zebrafish, Danio rerio
.
s, were found to be strong topoisomerase inhibitor
s in vitro, some of them were tested in vivo with similar results. Those substances share the properity with some chemotherapeutic anticancer drugs such etoposide
and doxorubicin
. When tested some natural phenols induced DNA
mutation
s in MLL gene
, which are common findings in neonatal acute leukemia
. The DNA changes were highly increased by treatment with flavonoids in cultured blood stem cells. Maternal high flavonoid
content diet is suspected to increase risk of particularly acute myeloid leukemia
in neonates. Natural phenols have both anticarcinogenic - proapoptotic effect and a carcinogenic, DNA damaging, mutagen
ic potential. Adults seem to rapidly metabolize most of phenols, so toxic, mutagen
ic effect may not be pronounced in regular low doses intaken with food. Some natural phenols - ex. EGCG
were found to rapidly induce detoxyfying Nrf2 transcription factor
activity which seems to be responsible for observed beneficial, antioxidative effects of the substances and also leads to rapid degradation of the phenolic molecules. However human embryos detoxification system is not mature enough to deal with phenols, which have possibility to cross the placenta barier. High intake of flavonoid
compounds during pregnancy is suspected to increase risk of neonatal leukemia. Therefore "bioflavonoid" supplements should be not used by pregnant women.
s, prenylated flavonoid
s and isoflavone
s. Bisphenol A
, a synthetic phenolic compound, is an endocrine disruptor
, which can mimic the body's own hormone
s and may lead to negative health effects.
can be performed using different solvents. There is a risk that polyphenol oxidase
(PPO) degrades the phenolic content of the sample therefore there is a need to use PPO inhibitors like potassium dithionite
(K2S2O4) or to perform experiment using liquid nitrogen
or to boil the sample for a few seconds (blanching) to inactivate the enzyme.
pKa
of phenolic compounds can be calculated from the retention time in liquid chromatography.
. Gallic acid
and isoflavone
s are the most well-absorbed phenols, followed by catechins (flavan-3-ol
s), flavanone
s, and quercetin
glucosides, but with different kinetics. The least well-absorbed phenols are the proanthocyanidins, galloylated tea catechins, and anthocyanin
s.
Detection can be made by recombinant luminescent bacterial sensor
s.
of genes. The Arabidopsis
regulatory gene Production of Anthocyanin
Pigment 1 (AtPAP1) can be expressed in other plant species.
Natural product
A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...
s. They are small molecules containing one or more phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
ic group. These molecules are smaller in size than polyphenol
Polyphenol
Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...
s, containing less than 12 phenolic groups. They can be classified as simple phenols (monophenols), with only one phenolic group, or di- (bi-), tri- and oligophenols, with two, three or several phenolic groups respectively. They can be found in plants and have an antioxidant activity. They are the most widely distributed class of plant secondary metabolite
Secondary metabolite
Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolities does not result in immediate death, but rather in long-term impairment of the organism's...
s and several thousand different compounds have been identified.
Names
As natural phenols are most often found in plants, authors use the genus or species name of the plant the particular molecule is found in to form its vernacular name. For example, the name of the anthocyanidin petunidinPetunidin
Petunidin is an O-methylated anthocyanidin. It is a natural organic compound and a particular type of anthocyanidin. It is a dark-red or purple water-soluble pigment found in many redberries including chokeberries , Saskatoon berries or different species of grape , and...
comes from Petunia
Petunia
Petunia is a widely cultivated genus of flowering plants of South American origin, closely related with tobacco, cape gooseberries, tomatoes, deadly nightshades, potatoes and chili peppers; in the family Solanaceae. The popular flower derived its name from French, which took the word petun, meaning...
or the name viniferin
Viniferin
Viniferin may refer to:* Alpha-viniferin, a resveratrol trimer* Delta-viniferin, a resveratrol dehydrodimer* Epsilon-viniferin, a resveratrol dimer...
comes from Vitis vinifera
Vitis vinifera
Vitis vinifera is a species of Vitis, native to the Mediterranean region, central Europe, and southwestern Asia, from Morocco and Portugal north to southern Germany and east to northern Iran....
.
Structural features
Simple and mid-molecular weight phenolic dimers and trimers phenol substructures have various further nomenclatures depending on the number of phenolic hydroxyl groups. A phenol, per se, is the term for a substructure with one phenolic hydroxyl group, catechol- and resorcinol-types (benzenediolBenzenediol
Benzenediols or dihydroxybenzenes are organic chemical compounds in which two hydroxyl groups are substituted onto a benzene ring. These aromatic compounds are classed as phenols, and more specifically as polyphenols...
s) have two, and pyrogallol- and phloroglucinol-types (benzenetriol
Benzenetriol
Benzenetriols or trihydroxybenzenes are aromatic chemical compounds and polyphenols in which three hydroxyl groups are substituted onto a benzene ring....
s) have three. Natural phenols may have heteroatom substituents other than hydroxyl groups; as might be expected, ether and ester linkages are common, as are various carboxylic acid derivatives.
| |
 |
|
 |
|
| Phenol Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds... |
Pyrocatechol Catechol, also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula C6H42. It is the ortho isomer of the three isomeric benzenediols. This colourless compound occurs naturally in trace amounts... |
Pyrogallol Pyrogallol or benzene-1,2,3-triol is a benzenetriol. It is a white crystalline powder and a powerful reducing agent. It was first prepared by Scheele 1786 by heating gallic acid. An alternate preparation is heating para-chlorophenoldisulphonic acid with potassium hydroxide.When in alkaline... |
Resorcinol Resorcinol is a dihydroxy benzene. It is the 1,3-isomer of benzenediol with the formula C6H42.-Nomenclature:Benzene-1,3-diol is the name recommended by the International Union of Pure and Applied Chemistry in its 1993 Recommendations for the Nomenclature of Organic Chemistry.-Production:It is... |
Phloroglucinol Phloroglucinol is a benzenetriol. It is an organic compound that is used in the synthesis of pharmaceuticals and explosives. This molecule exists in two forms, or tautomers, 1,3,5-trihydroxybenzene, which has phenol-like, and 1,3,5-cyclohexanetrione , which has ketone-like character. These two... |
Natural phenol compositions are normally limited to carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
, hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
and oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
in undefined proportion. As a class, they do not contain nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, element characteristic of amino-acids (see tyrosine
Tyrosine
Tyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...
and L-DOPA), catecholamine
Catecholamine
Catecholamines are molecules that have a catechol nucleus consisting of benzene with two hydroxyl side groups and a side-chain amine. They include dopamine, as well as the "fight-or-flight" hormones adrenaline and noradrenaline released by the adrenal medulla of the adrenal glands in response to...
hormones or alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s.
Chemical properties
The majority of these compounds are solubles molecules but the smaller molecules can be volatiles.Natural phenols spectral data show a typical UV
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
absorbance characteristic of benzene aromaticity at 270 nm. However, according to Woodward's rules
Woodward's rules
Woodward's rules, named after Robert Burns Woodward and also known as Woodward-Fieser rules are several sets of empirically derived rules which attempt to predict the wavelength of the absorption maximum in an ultraviolet-visible spectrum of a given compound...
, bathochromic shift
Bathochromic shift
Bathochromic shift is a change of spectral band position in the absorption, reflectance, transmittance, or emission spectrum of a molecule to a longer wavelength ....
s often happen suggesting the presence of delocalised π electrons arising from a conjugation between the benzene and vinyl
Vinyl
A vinyl compound is any organic compound that contains a vinyl group ,which are derivatives of ethene, CH2=CH2, with one hydrogen atom replaced with some other group...
s groups.
Many natural phenols present chirality
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
within their molecule. An example of such molecules is catechin
Catechin
Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....
. Cavicularin
Cavicularin
Cavicularin is a natural phenolic secondary metabolite isolated from the liverwort Cavicularia densa. This macrocycle is unusual because it was the first compound isolated from nature displaying optical activity due to the presence of planar chirality and axial chirality. The specific rotation for...
is a unusual macrocycle because it was the first compound isolated from nature displaying optical activity due to the presence of planar chirality
Planar chirality
Planar chirality is the special case of chirality for two dimensions.Most fundamentally, planar chirality is a mathematical term, finding use in chemistry, physics and related physical sciences, for example, in astronomy, optics and metamaterials...
and axial chirality
Axial chirality
Axial chirality is a special case of chirality in which a molecule does not possess a stereogenic center but an axis of chirality – an axis about which a set of substituents is held in a spatial arrangement that is not superposable on its mirror image...
.
Natural phenols chemically interact with many other substances. Stacking
Stacking (chemistry)
In chemistry, pi stacking refers to attractive, noncovalent interactions between aromatic rings. These interactions are historically thought to be important in to base stacking of DNA nucleotides, protein folding, template-directed synthesis, materials science, and molecular recognition, although...
, a chemical property of molecules with aromaticity, is seen occurring between phenolic molecules. When studied in mass spectrometry, phenols easily form adduct ions with halogens. They can also interact with the food matrices or with different forms of silica (mesoporous silica
Mesoporous silica
Mesoporous silica is a form of silica and a recent development in nanotechnology. The most common types of mesoporous nanoparticles are MCM-41 and SBA-15. Research continues on the particles, which have applications in catalysis, drug delivery and imaging....
, fumed silica
Fumed silica
Fumed silica, also known as pyrogenic silica because it is produced in a flame, consists of microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk...
or silica-based sol gel
Sol gel
The sol-gel process is a wet-chemical technique widely used in the fields of materials science and ceramic engineering. Such methods are used primarily for the fabrication of materials starting from a colloidal solution that acts as the precursor for an integrated network of either discrete...
s).
The largest and best studied natural phenols are the flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
s, which include several thousand compounds, among them the flavonols, flavones, flavan-3ol (catechins), flavanone
Flavanone
The flavanones are a type of flavonoids. They are generally glycosylated by a disaccharide at position seven to give flavanone glycosides.-List of flavanones:* Butin* Eriodictyol* Hesperetin* Hesperidin* Homoeriodictyol* Isosakuranetin* Naringenin...
s, anthocyanidin
Anthocyanidin
Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium, which is a type of oxonium ion . They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the...
s and isoflavonoid
Isoflavonoid
Isoflavonoids are a class of flavonoid polyphenolic compounds. They are biologically active compounds, such as phytoestrogens, produced by pea family plants.Isoflavonoids are derived from the flavonoid biosynthesis pathway via liquiritigenin or naringenin....
s.
| Base Unit: |  Gallic acid Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of... |
 |
Cinnamic acid Cinnamic acid is a white crystalline organic acid, which is slightly soluble in water.It is obtained from oil of cinnamon, or from balsams such as storax. It is also found in shea butter and is the best indication of its environmental history and post-extraction conditions... |
|---|---|---|---|
| Class/Polymer: | Hydrolyzable tannins | Flavonoid Flavonoid Flavonoids , are a class of plant secondary metabolites.... , Condensed tannins |
Lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood... s |
The phenolic unit can be found dimerized or further polymerized, creating a new class of polyphenol. For example, ellagic acid
Ellagic acid
Ellagic acid is a natural phenol antioxidant found in numerous fruits and vegetables including blackberries, raspberries, strawberries, cranberries, walnuts, pecans, pomegranates, wolfberry and other plant foods...
is a dimer of gallic acid and forms the class of ellagitannins, or a catechin
Catechin
Catechin is a natural phenol antioxidant plant secondary metabolite. The term catechins is also commonly used to refer to the related family of flavonoids and the subgroup flavan-3-ols ....
and a gallocatechin can combine to form the red compound theaflavin
Theaflavin
Theaflavin and its derivatives, known collectively as theaflavins, are antioxidant polyphenols that are formed from flavan-3-ols such as in tea leaves during the enzymatic oxidation of tea leaves, such as in black tea. Theaflavins are types of thearubigins, and are therefore reddish in color...
, a process which also results in the large class of brown thearubigin
Thearubigin
Thearubigins are polymeric polyphenols that are formed during the enzymatic oxidation of tea leaves. Thearubigins are red in colour. Therefore a black tea gives a reddish liquor while a green or white tea gives a much clearer one...
s in tea.
Two natural phenols from two different categories, for instance a flavonoid and a lignan, can combine to form a hybrid class like the flavonolignan
Flavonolignan
-Examples:Flavonolignans identified in Silybum marianum silymarin complex include silibinin, silychristin, silydianin, dehydrosilybin, deoxysilycistin, deoxysilydianin, silandrin, silybinome, silyhermin and neosilyhermin and can be produced in vitro. Silibinin is found in the roots of S...
s.
Classification
There is a classification based on number of carbons based on HarborneJeffrey Harborne
Jeffrey Barry Harborne FRS was the Professor of Botany at the University of Reading, 1976–93, then Professor emeritus. He specialised in phytochemistry. He contributed to more than 40 books and 270 research papers and was a pioneer in ecological biochemistry, particularly in the complex chemical...
et al., published in 1980:
| Number of carbon atoms | Basic skeleton | Number of phenolic cycles | Class | Examples |
|---|---|---|---|---|
| 6 | C6 | 1 | Simple phenols, Benzoquinones | Catechol, Hydroquinone, 2,6-Dimethoxybenzoquinone |
| 7 | C6-C1 | 1 | Phenolic acid Phenolic acid Phenolic acids are a type of organic compounds. Included in that class are substances containing a phenolic ring and an organic carboxylic acid function .... s, Phenolic aldehyde Phenolic aldehyde Phenolic aldehydes are a type of natural phenol. Phenolics aldehydes can be found in wines and cognacs.Examples :* Hydroxybenzaldehydes* Protocatechuic aldehyde* Vanillin and isovanillin... s |
Gallic, salicylic acids |
| 8 | C6-C2 | 1 | Acetophenone Acetophenone Acetophenone is the organic compound with the formula C6H5CCH3. It is the simplest aromatic ketone. This colourless, viscous liquid is a precursor to useful resins and fragrances.-Production:Acetophenone can be obtained by a variety of methods... s, Tyrosine derivatives , Phenylacetic acid Phenylacetic acid Phenylacetic acid is an organic compound containing a phenyl functional group and a carboxylic acid functional group. It is a white solid with a disagreeable odor... s |
3-Acetyl-6-methoxybenzaldehyde, Tyrosol, p-Hydroxyphenylacetic acid |
| 9 | C6-C3 | 1 | Hydroxycinnamic acid Hydroxycinnamic acid Hydroxycinnamic acids are a class of polyphenols having a C6-C3 skeleton. These compounds are hydroxy derivatives of cinnamic acid.In the category of phytochemicals that can be found in food, there are :* Alpha-cyano-4-hydroxycinnamic acid... s, Phenylpropene Phenylpropene Phenylpropenes, propenylphenols or allylbenzenes are a class of phenylpropanoids, a type of polyphenols.The phenylpropenes, including eugenol, chavicol, safrole and estragole, are derived from the monolignols. These compounds are the primary constituents of various essential oils.... s, Coumarin Coumarin Coumarin is a fragrant chemical compound in the benzopyrone chemical class, found in many plants, notably in high concentration in the tonka bean , vanilla grass , sweet woodruff , mullein , sweet grass , cassia cinnamon and sweet clover... s, Isocoumarin Isocoumarin Isocoumarin is a lactone, a type of natural organic compound.-Known natural compounds:* Thunberginol A and Bdihydroisocoumarins* Hydrangenol* Phyllodulcin* Thunberginol C, D, E and G... s, Chromone Chromone Chromone is a derivative of benzopyran with a substituted keto group on the pyran ring. It is an isomer of coumarin.Derivatives of chromone are collectively known as chromones... s |
Caffeic, ferulic acids, Myristicin, Eugenol, Umbelliferone, aesculetin, Bergenon, Eugenin |
| 10 | C6-C4 | 1 | Naphthoquinone Naphthoquinone Naphthoquinone is a class of natural phenols based on the C6-C4 skeleton.1,4-Naphthoquinone can be viewed as derivatives of naphthalene through the replacement of two hydrogen atoms by two ketone groups.... s |
Juglone, Plumbagin |
| 13 | C6-C1-C6 | 2 | Xanthonoid Xanthonoid A xanthonoid is a chemical natural phenolic compound formed from the xanthone backbone. Many members of the Clusiaceae contain xanthonoids.Xanthonoid biosynthesis in cell cultures of Hypericum androsaemum involves the presence of a benzophenone synthase condensing a molecule of benzoyl-CoA with... s |
Mangiferin |
| 14 | C6-C2-C6 | 2 | Stilbenoids, Anthraquinone Anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene is an aromatic organic compound with formula . Several isomers are possible, each of which can be viewed as a quinone derivative... s |
Resveratrol, Emodin |
| 15 | C6-C3-C6 | 2 | Chalconoid Chalconoid Chalconoids, also known as chalcones, are natural phenols related to chalcone. They form the central core for a variety of important biological compounds. They show antibacterial, antifungal, antitumor and anti-inflammatory properties... s, Flavonoid Flavonoid Flavonoids , are a class of plant secondary metabolites.... s, Isoflavonoids, Neoflavonoids |
Quercetin, cyanidin, Genistein |
| 18 | (C6-C3)2 | 2 | Lignan Lignan The lignans are a group of chemical compounds found in plants. Lignans are one of the major classes of phytoestrogens, which are estrogen-like chemicals and also act as antioxidants. The other classes of phytoestrogens are the isoflavones and coumestans... s, Neolignans |
Pinoresinol, Eusiderin |
| 30 | (C6-C3-C6)2 | 4 | Biflavonoids | Amentoflavone |
| many | (C6-C3)n, (C6)n, (C6-C3-C6)n |
n > 12 | Lignin Lignin Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood... s, Catechol melanin Catechol melanin Catechol melanins are plant melanins. They yield catechol on alkali fusion. This type of substance can be found in fungi like Ustilago. Indole-5,6-quinone is a chemical compound found in the oxidative browning reaction of fruits like bananas mediated by polyphenol oxidase from tyrosine and... s, Flavolans (Condensed tannins), Polyphenolic protein Polyphenolic protein Polyphenolic proteins are proteins produced by some algae and marine invertebrates like the blue mussel, Mytilus edulis or the polychaete Phragmatopoma californica that are used as bioadhesives. These proteins contain a high level of L-DOPA and cystine.... s, Polyphenol Polyphenol Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units... s |
Raspberry ellagitannin Raspberry ellagitannin The raspberry ellagitannin is an ellagitannin found in raspberries. It is a polyphenol per se, containing 6 ellagic acid-type components and two additional monomeric phenolics, for a total of 14 gallic acid units .... , Tannic acid Tannic acid Tannic acid is a specific commercial form of tannin, a type of polyphenol. Its weak acidity is due to the numerous phenol groups in the structure... |
Ecology
Phenolic compounds are found in plants. They can also be found in mushroom basidiomycetes species. For example, protocatechuic acidProtocatechuic acid
Protocatechuic acid is a dihydroxybenzoic acid, a type of phenolic acid. It has mixed effects on normal and cancer cells in in vitro and in vivo studies.-Biological effects:...
and pyrocatechol
Pyrocatechol
Catechol, also known as pyrocatechol or 1,2-dihydroxybenzene, is an organic compound with the molecular formula C6H42. It is the ortho isomer of the three isomeric benzenediols. This colourless compound occurs naturally in trace amounts...
are found in Agaricus bisporus as well as other phenylated substances like phenylacetic
Phenylacetic acid
Phenylacetic acid is an organic compound containing a phenyl functional group and a carboxylic acid functional group. It is a white solid with a disagreeable odor...
and phenylpyruvic acid
Phenylpyruvic acid
Phenylpyruvic acid is a pyruvic acid derivative.-See also:* Phenylpyruvate decarboxylase* Phenylpyruvate tautomerase* Phenylketonuria...
s. The hardening of the protein component of insect cuticle has been shown to be due to the tanning action of an agent produced by oxidation of a phenolic substance. In the analogous hardening of the cockroach ootheca
Ootheca
An ootheca is a type of egg mass made by any member of a variety of species .The word is a latinized combination of oo-, meaning "egg", from the Greek word ōon , and theca, meaning a "cover" or "container", from the Greek theke...
, the phenolic substance concerned is 3:4-dihydroxybenzoic acid (protocatechuic acid
Protocatechuic acid
Protocatechuic acid is a dihydroxybenzoic acid, a type of phenolic acid. It has mixed effects on normal and cancer cells in in vitro and in vivo studies.-Biological effects:...
).
Natural phenols can be involved in allelopathic
Allelopathy
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial or detrimental effects on the target organisms...
interactions in soil. Juglone
Juglone
Juglone, also called 5-hydroxy-1,4-naphthalenedione or 5-hydroxynaphthoquinone, is an organic compound with the molecular formula C10H6O3. In the food industry, juglone is also known as C.I. Natural Brown 7 and C.I. 75500...
is an example of such a molecule inhibiting the growth of other plant species around walnut trees. The nodule formation in Medicago truncatula
Medicago truncatula
Medicago truncatula is a small legume native to the Mediterranean region that is used in genomic research. It is a low-growing, clover-like plant 10–60 cm tall with trifoliate leaves. Each leaflet is rounded, 1–2 cm long, often with a dark spot in the center...
is apparently dependent on the flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
s pathway. Pterocarpan
Pterocarpan
Pterocarpans are derivatives of isoflavonoids found in the Fabaceae family. It is a group of compounds which can be described as benzo-pyrano-furano-benzenes Pterocarpans are derivatives of isoflavonoids found in the Fabaceae family. It is a group of compounds which can be described as...
s serve as phytoalexin
Phytoalexin
Phytoalexins are antimicrobial substances synthesized de novo by plants that accumulate rapidly at areas of incompatible pathogen infection. They are broad spectrum inhibitors and are chemically diverse with different types characteristic of particular plant species...
s in Trifolium pratense and other Fabaceae.
Furanocoumarin
Furanocoumarin
Furanocoumarins, or furocoumarins, are a class of organic chemical compounds produced by a variety of plants. They are biosynthesized partly through the phenylpropanoid pathway and the mevalonate pathway, which is biosynthesized by a coupling of dimethylallyl pyrophosphate and 7-hydroxycoumarin...
s are phenolic and are non-toxic until activated by light. Furancoumarins block the transcription and repair of DNA. Therefore, they are considered phytotoxin
Phytotoxin
Phytotoxin refers to a substance produced by a plant that is toxic or a substance that is toxic to the plant Many substances produced by plants are secondary metabolites and are the by-products of primary physiological processes...
s.
Natural phenols can be enzymatically polymerised. Laccase
Laccase
Laccases are copper-containing oxidase enzymes that are found in many plants, fungi, and microorganisms. The copper is bound in several sites; Type 1, Type 2, and/or Type 3. The ensemble of types 2 and 3 copper is called a trinuclear cluster . Type 1 copper is available to action of solvents,...
and peroxidase
Peroxidase
Peroxidases are a large family of enzymes that typically catalyze a reaction of the form:For many of these enzymes the optimal substrate is hydrogen peroxide, but others are more active with organic hydroperoxides such as lipid peroxides...
induced the polymerization of syringic acid
Syringic acid
Syringic acid is a naturally occurring O-methylated trihydroxybenzoic acid, a type of chemical compound. It can be found in the açaí palm and its oil , in Ardisia elliptica...
to give a poly(1,4-phenylene oxide) bearing a carboxylic acid at one end and a phenolic hydroxyl group at the other.
In soils, it is assumed that larger amounts of phenols are released from decomposing plant litter
Plant litter
Plant litter, leaf litter or tree litter is dead plant material, such as leaves, bark, needles, and twigs, that has fallen to the ground. Litter provides habitat for small animals, fungi, and plants, and the material may be used to construct nests. As litter decomposes, nutrients are released to...
rather than from throughfall
in any natural plant community. In the soil, soluble phenols face four different fates. They might be degraded and mineralized as a carbon source by heterotrophic microorganisms; they can be transformed into insoluble and recalcitrant humic
Humic acid
Humic acid is a principal component of humic substances, which are the major organic constituents of soil , peat, coal, many upland streams, dystrophic lakes, and ocean water. It is produced by biodegradation of dead organic matter...
substances by polymerization and condensation reactions (with the contribution of soil organisms); they might adsorb to clay minerals or form chelates with aluminium or iron ions; or they might remain in dissolved form, leached by percolating water, and finally leave the ecosystem as part of dissolved organic carbon (DOC).
Volatile phenolic compounds are found in plant resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
where they may attract benefactors such as parasitoid
Parasitoid
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host...
s or predators of the herbivores that attack the plant.
Biological uses
FuranoflavonoidFuranoflavonoid
Furanoflavonoid are flavonoids possessing a furan group.An example of such compound is karanjin, a furanoflavonol....
s like karanjin
Karanjin
Karanjin, a furanoflavonol, a type of flavonoid. It is obtained from the seeds of the karanja tree , a tree growing wild in south India. Karanjin is an acaricide and insecticide. Acaricide means a product that is used to kill mites...
or rotenoid
Rotenoid
Rotenoids are naturally occurring substances containing a cis-fused tetrahydrochromeno[3,4-b]chromene nucleus. Rotenoids are related to the isoflavones....
s are used as acaricide or insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...
.
Biosynthesis
Most of the natural phenols are derived from secondary plant metabolism of the shikimic acidShikimic acid
Shikimic acid, more commonly known as its anionic form shikimate, is an important biochemical metabolite in plants and microorganisms. Its name comes from the Japanese flower shikimi , from which it was first isolated....
pathway, malic acid
Malic acid
Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. It is a dicarboxylic acid which is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms , though only the L-isomer exists...
pathway or both. The aromatic amino acid phenylalanine
Phenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
, synthesized in the shikimic-acid pathway, is the common precursor of phenol containing amino acids and phenolic compounds.
In plants, the phenolic units are ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
ified or methylated
Methylation
In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...
. The polyphenols are submitted to conjugation. Many natural phenols are found in the glycoside
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...
form instead of the aglycone
Aglycone
An aglycone is the non-sugar compound remaining after replacement of the glycosyl group from a glycoside by a hydrogen atom. The spelling aglycon is sometimes encountered .Classes of phytochemicals found in the aglycone and glycosides forms :...
form.
In olive oil, tyrosol
Tyrosol
Tyrosol is a natural phenolic antioxidant present in a variety of natural sources. The principal source in the human diet is olive oil. Tyrosol is a derivative of phenethyl alcoholAs an antioxidant, tyrosol can protect cells against injury due to oxidation...
forms esters with fatty acids. In rye, alkylresorcinols are phenolic lipids.
Some acetylations involve terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
s like geraniol
Geraniol
Geraniol is a monoterpenoid and an alcohol. It is the primary part of rose oil, palmarosa oil, and citronella oil . It also occurs in small quantities in geranium, lemon, and many other essential oils. It appears as a clear to pale-yellow oil that is insoluble in water, but soluble in most common...
. Those molecules are called meroterpenes (a chemical compound having a partial terpenoid structure).
Methylations can occur by the formation of an ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
bond on hydroxyl groups forming O-methylated polyphenols. In the case of the O-methylated flavone tangeritin
Tangeritin
Tangeritin is an O-polymethoxylated flavone that is found in tangerine and other citrus peels. Tangeritin strengthens the cell wall and protects it from invasion ....
, all of the five hydroxyls are methylated, leaving no free hydroxyls of the phenol group. Methylations can also occur on directly on a carbon of the benzene ring like in the case of poriol
Poriol
Poriol is a C-methylated flavanone, a type of flavonoid. It is found in Pseudotsuga menziesii in reaction to infection by Poria weirii....
, a C-methylated flavonoid
C-methylated flavonoid
The C-methylated flavonoids are a category of flavonoid having methylation on carbon.An example of such compounds is the flavanone poriol....
.
In animals and humans, after ingestion, polyphenols become part of the xenobiotic metabolism
Xenobiotic metabolism
Xenobiotic metabolism is the set of metabolic pathways that modify the chemical structure of xenobiotics, which are compounds foreign to an organism's normal biochemistry, such as drugs and poisons...
. In subsequent phase II reactions, these activated metabolites are conjugated with charged species such as glutathione
Glutathione
Glutathione is a tripeptide that contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side-chain...
, sulfate
Sulfate
In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
, glycine
Glycine
Glycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...
or glucuronic acid
Glucuronic acid
Glucuronic acid is a carboxylic acid. Its structure is similar to that of glucose. However, glucuronic acid's sixth carbon is oxidized to a carboxylic acid...
. These reactions are catalysed by a large group of broad-specificity transferases.
Content in human food
Notable sources of natural phenols include berriesBerry
The botanical definition of a berry is a fleshy fruit produced from a single ovary. Grapes are an example. The berry is the most common type of fleshy fruit in which the entire ovary wall ripens into an edible pericarp. They may have one or more carpels with a thin covering and fleshy interiors....
, tea
Tea
Tea is an aromatic beverage prepared by adding cured leaves of the Camellia sinensis plant to hot water. The term also refers to the plant itself. After water, tea is the most widely consumed beverage in the world...
, beer
Beer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...
, olive oil
Olive oil
Olive oil is an oil obtained from the olive , a traditional tree crop of the Mediterranean Basin. It is commonly used in cooking, cosmetics, pharmaceuticals, and soaps and as a fuel for traditional oil lamps...
, chocolate
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...
or cocoa
Cocoa solids
Cocoa solids are the low-fat component of chocolate. When sold as an end product, it may also be called cocoa powder, cocoa, and cacao....
, coffee
Coffee
Coffee is a brewed beverage with a dark,init brooo acidic flavor prepared from the roasted seeds of the coffee plant, colloquially called coffee beans. The beans are found in coffee cherries, which grow on trees cultivated in over 70 countries, primarily in equatorial Latin America, Southeast Asia,...
, pomegranate
Pomegranate
The pomegranate , Punica granatum, is a fruit-bearing deciduous shrub or small tree growing between five and eight meters tall.Native to the area of modern day Iran, the pomegranate has been cultivated in the Caucasus since ancient times. From there it spread to Asian areas such as the Caucasus as...
s, popcorn
Popcorn
Popcorn, or popping corn, is corn which expands from the kernel and puffs up when heated. Corn is able to pop because, like sorghum, quinoa and millet, its kernels have a hard moisture-sealed hull and a dense starchy interior. This allows pressure to build inside the kernel until an explosive...
, yerba mate
Yerba mate
Maté, yerba maté or erva maté , Ilex paraguariensis, is a species of holly native to subtropical South America in northeastern Argentina, Bolivia, southern Brazil, Uruguay and Paraguay...
, fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
s and fruit based drinks (including cider and wine) and vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
s. Herb
Herb
Except in botanical usage, an herb is "any plant with leaves, seeds, or flowers used for flavoring, food, medicine, or perfume" or "a part of such a plant as used in cooking"...
s and spice
Spice
A spice is a dried seed, fruit, root, bark, or vegetative substance used in nutritionally insignificant quantities as a food additive for flavor, color, or as a preservative that kills harmful bacteria or prevents their growth. It may be used to flavour a dish or to hide other flavours...
s, nut
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...
s (walnuts, peanut) and algae are also potentially significant for supplying certain natural phenols. Such food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...
s containing natural phenols are generally considered as health food
Health food
The term health food is generally used to describe foods that are considered to be beneficial to health, beyond a normal healthy diet required for human nutrition. However, the term is not precisely defined by national regulatory agencies such as the U.S...
.
Natural phenols can also be found in fatty matrices like olive oil
Olive oil
Olive oil is an oil obtained from the olive , a traditional tree crop of the Mediterranean Basin. It is commonly used in cooking, cosmetics, pharmaceuticals, and soaps and as a fuel for traditional oil lamps...
. Cloudy olive oil
Cloudy olive oil
Cloudy olive oil is an intermediate product of olive oil extraction. It is actually the initial cloudy juice of the olive drupes soon after crushing, separation and decanting and before final filtration...
has the higher levels of phenols, or polar phenols that form a complex phenol-protein complex.
Phenolic compounds, when used in beverages, such as prune juice, have been shown to be helpful in the color and sensory components, such as alleviating bitterness.
Antioxidant activity
As interpreted by the Linus Pauling InstituteLinus Pauling Institute
The Linus Pauling Institute is a research institute located at Oregon State University with a focus on health maintenance. The mission statement of the institute is three-fold. First, to determine the functional roles of micronutrients and phytochemicals in promoting optimal health and to treat or...
and the European Food Safety Authority
European Food Safety Authority
The European Food Safety Authority is an agency of the European Union that provides independent scientific advice and communication on existing and emerging risks associated with the food chain, created by European Regulation 178/2002....
(EFSA), dietary flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
s have little or no direct antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
food value following digestion. Not like controlled test tube conditions, the fate of natural phenols in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
shows they are poorly conserved (less than 5%), with most of what is absorbed existing as chemically-modified metabolites destined for rapid excretion.
Cinnamates have been shown to have more antioxidant activity when exposed in vitro to the Fenton reaction (catalytic Fe(II) with hydrogen peroxide) than the other natural phenols present in wine.
In vitro effects
Mainly from in vitro studies, natural phenols have been reported to have antimicrobialAntimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
, antiviral
Antiviral
Antiviral may refer to:*Antiviral drug*Antiviral protein*Antivirus software*Antiviral Therapy, an academic journal...
, anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....
, and vasodilatory actions.
Epigallocatechin gallate
Epigallocatechin gallate
Epigallocatechin gallate , also known as epigallocatechin 3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin....
(EGCG), a flavanol found in tea, may have an effect on cancer by inhibiting DNA methyltransferase
DNA methyltransferase
In biochemistry, the DNA methyltransferase family of enzymescatalyze the transfer of a methyl group to DNA. DNA methylation serves a wide variety of biological functions...
activity. It has been shown to reduce reactive oxygen species
Reactive oxygen species
Reactive oxygen species are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons....
levels in vitro.
The natural phenol resveratrol
Resveratrol
Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....
inhibits occurrence and/or growth of experimental tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s.
Research with biological model species
Natural phenols such as resveratrolResveratrol
Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....
activate human SIRT1, extend the lifespan of budding yeast, Saccharomyces cerevisiae
Saccharomyces cerevisiae
Saccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental to baking and brewing since ancient times. It is believed that it was originally isolated from the skin of grapes...
, and may be sirtuin-activating compound
Sirtuin-activating compound
Sirtuin-activating compounds are chemical compounds having an effect on sirtuins, a group of enzymes that use NAD+ to remove acetyl groups from proteins. They are caloric restriction mimetic candidates, molecules able to prevent aging-related diseases like Alzheimer's , diabetes, and...
s. Other examples of such products are butein
Butein
Butein is a chalconoid. It can be found in Toxicodendron vernicifluum . It has antioxidative, aldose reductase and advanced glycation endproducts inhibitory effects. It is also a sirtuin-activating compound, a chemical compound having an effect on sirtuins, a group of enzymes that use NAD+ to...
, piceatannol
Piceatannol
Piceatannol is a stilbenoid, a type of phenolic compound. It is a metabolite of resveratrol found in red wine.Astringin is a piceatannol glucoside.-Health effects:...
, isoliquiritigenin
Isoliquiritigenin
Isoliquiritigenin is a licorice chalconoid, a type of natural phenols. It is currently under experimentation phase testing for use as a cancer treatment as well as an aide for cocaine addiction...
, fisetin
Fisetin
Fisetin is a flavonol, a structurally distinct chemical substance that belongs to the flavonoid group of polyphenols. It can be found in many plants, where it serves as a colouring agent...
, and quercetin
Quercetin
Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...
. Longevity
Longevity
The word "longevity" is sometimes used as a synonym for "life expectancy" in demography or known as "long life", especially when it concerns someone or something lasting longer than expected ....
increased by resveratrol
Resveratrol
Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....
was demonstrated in Caenorhabditis elegans
Caenorhabditis elegans
Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
and Drosophila melanogaster
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
. This longevity increase may be due to a caloric restriction effect. Resveratrol
Resveratrol
Resveratrol is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants when under attack by pathogens such as bacteria or fungi....
also increases the lifespan of vertebrates as has been demonstrated in short-lived fish, Nothobranchius furzeri
Nothobranchius furzeri
The turquoise killifish is a species of fish in the Aplocheilidae branch of the Cyprinodontiformes order. This annual fish inhabits ephemeral pools in semi-arid areas with scarce and erratic precipitations and have adapted to the routine drying of their environment by evolving...
.
Other experiments on Drosophila melanogaster
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
indicate that natural phenols (gallic acid
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
, ferulic acid
Ferulic acid
Ferulic acid is a hydroxycinnamic acid, a type of organic compound. It is an abundant phenolic phytochemical found in plant cell wall components such as arabinoxylans as covalent side chains. It is related to trans-cinnamic acid. As a component of lignin, ferulic acid is a precursor in the...
, caffeic acid
Caffeic acid
Caffeic acid is a hydroxycinnamic acid, a naturally occurring organic compound. This yellow solid consists of both phenolic and acrylic functional groups...
, coumaric acid
Coumaric acid
Coumaric acid is a hydroxycinnamic acid, an organic compound that is a hydroxy derivative of cinnamic acid. There are three isomers, o-coumaric acid, m-coumaric acid, and p-coumaric acid, that differ by the position of the hydroxy substitution of the phenyl group...
, propyl gallate
Propyl gallate
Propyl gallate, or propyl 3,4,5-trihydroxybenzoate is an ester formed by the condensation of gallic acid and propanol. Since 1948, this antioxidant has been added to foods containing oils and fats to prevent oxidation. As a food additive, it is used under the E number E310.-Description:Propyl...
, epicatechin, epigallocatechin, and epigallocatechin gallate
Epigallocatechin gallate
Epigallocatechin gallate , also known as epigallocatechin 3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin....
) may influence mechanisms related to Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
. Quercetin
Quercetin
Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...
and rutin
Rutin
Rutin, also called rutoside, quercetin-3-O-rutinoside and sophorin, is a citrus flavonoid glycoside found in buckwheat, the leaves and petioles of Rheum species, and asparagus...
act against scopolamine
Scopolamine
Scopolamine, also known as levo-duboisine, and hyoscine, is a tropane alkaloid drug with muscarinic antagonist effects. It is among the secondary metabolites of plants from Solanaceae family of plants, such as henbane, jimson weed and Angel's Trumpets , and corkwood...
-induced memory impairment in zebrafish, Danio rerio
Danio rerio
The zebrafish, Danio rerio, is a tropical freshwater fish belonging to the minnow family of order Cypriniformes. It is a popular aquarium fish, frequently sold under the trade name zebra danio, and is an important vertebrate model organism in scientific research.-Taxonomy:The zebrafish are...
.
Neonatal carcinogenesis
Many natural phenols, like the flavonoidFlavonoid
Flavonoids , are a class of plant secondary metabolites....
s, were found to be strong topoisomerase inhibitor
Topoisomerase inhibitor
Topoisomerase inhibitors are agents designed to interfere with the action of topoisomerase enzymes , which are enzymes that control the changes in DNA structure by catalyzing the breaking and rejoining of the phosphodiester backbone of DNA strands during the normal cell cycle.In recent years,...
s in vitro, some of them were tested in vivo with similar results. Those substances share the properity with some chemotherapeutic anticancer drugs such etoposide
Etoposide
Etoposide phosphate is an anti-cancer agent. It is known in the laboratory as a topoisomerase poison. Etoposide is often incorrectly referred to as a topoisomerase inhibitor in order to avoid using the term "poison" in a clinical setting...
and doxorubicin
Doxorubicin
Doxorubicin INN is a drug used in cancer chemotherapy. It is an anthracycline antibiotic, closely related to the natural product daunomycin, and like all anthracyclines, it works by intercalating DNA....
. When tested some natural phenols induced DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
s in MLL gene
MLL (gene)
Histone-lysine N-methyltransferase HRX is an enzyme that in humans is encoded by the MLL gene.MLL is a histone methyltransferase deemed a positive global regulator of gene transcription...
, which are common findings in neonatal acute leukemia
Acute leukemia
Acute leukemia or acute leukaemia is a generic term used to describe a family of serious medical conditions relating to an original diagnosis of leukemia...
. The DNA changes were highly increased by treatment with flavonoids in cultured blood stem cells. Maternal high flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
content diet is suspected to increase risk of particularly acute myeloid leukemia
Acute myeloid leukemia
Acute myeloid leukemia , also known as acute myelogenous leukemia, is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute...
in neonates. Natural phenols have both anticarcinogenic - proapoptotic effect and a carcinogenic, DNA damaging, mutagen
Mutagen
In genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are therefore also likely to be carcinogens...
ic potential. Adults seem to rapidly metabolize most of phenols, so toxic, mutagen
Mutagen
In genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. As many mutations cause cancer, mutagens are therefore also likely to be carcinogens...
ic effect may not be pronounced in regular low doses intaken with food. Some natural phenols - ex. EGCG
Epigallocatechin gallate
Epigallocatechin gallate , also known as epigallocatechin 3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin....
were found to rapidly induce detoxyfying Nrf2 transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...
activity which seems to be responsible for observed beneficial, antioxidative effects of the substances and also leads to rapid degradation of the phenolic molecules. However human embryos detoxification system is not mature enough to deal with phenols, which have possibility to cross the placenta barier. High intake of flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
compounds during pregnancy is suspected to increase risk of neonatal leukemia. Therefore "bioflavonoid" supplements should be not used by pregnant women.
Other adverse effects
Phytoestrogens mainly belong to a large group of substituted natural phenolic compounds : the coumestanCoumestan
Coumestan is an organic compound that is a derivative of coumarin. Coumestan forms the central core of a variety of natural compounds known collectively as coumestans. Coumestans, including coumestrol, a phytoestrogen, are found in a variety of plants...
s, prenylated flavonoid
Prenylated flavonoid
Prenylated favonoids are a sub-class of flavonoids. They are widely distributed throughout the plant kingdom. Some are known to have phytoestrogenic or antioxidant properties. They are given in the list of adaptogens in herbalism....
s and isoflavone
Isoflavone
Isoflavones comprise a class of organic compounds, often naturally occurring, related to the isoflavonoids. Many act as phytoestrogens in mammals...
s. Bisphenol A
Bisphenol A
Bisphenol A is an organic compound with two phenol functional groups. It is used to make polycarbonate plastic and epoxy resins, along with other applications....
, a synthetic phenolic compound, is an endocrine disruptor
Endocrine disruptor
Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...
, which can mimic the body's own hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s and may lead to negative health effects.
Research
ExtractionExtraction (chemistry)
Extraction in chemistry is a separation process consisting in the separation of a substance from a matrix. It may refer to Liquid-liquid extraction, and Solid phase extraction....
can be performed using different solvents. There is a risk that polyphenol oxidase
Polyphenol oxidase
Polyphenol oxidase is a tetramer which contains four atoms of copper per molecule, and binding sites for two aromatic compounds and oxygen...
(PPO) degrades the phenolic content of the sample therefore there is a need to use PPO inhibitors like potassium dithionite
Dithionite
The dithionite anion , is an oxoanion of sulfur formally derived from dithionous acid, H2S2O4.-Chemistry:Dithionous acid has not been detected either as a pure compound or in solution....
(K2S2O4) or to perform experiment using liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...
or to boil the sample for a few seconds (blanching) to inactivate the enzyme.
pKa
PKA
PKA, pKa, or other similar variations may stand for:* pKa, the symbol for the acid dissociation constant at logarithmic scale* Protein kinase A, a class of cAMP-dependent enzymes* Pi Kappa Alpha, the North-American social fraternity...
of phenolic compounds can be calculated from the retention time in liquid chromatography.
Bioavailability
Questions on the relationship between health benefits and polyphenols generally revolve around bioavailabilityBioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...
. Gallic acid
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
and isoflavone
Isoflavone
Isoflavones comprise a class of organic compounds, often naturally occurring, related to the isoflavonoids. Many act as phytoestrogens in mammals...
s are the most well-absorbed phenols, followed by catechins (flavan-3-ol
Flavan-3-ol
Flavan-3-ols are a class of flavonoids that use the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. These compounds include the catechins and the catechin gallates....
s), flavanone
Flavanone
The flavanones are a type of flavonoids. They are generally glycosylated by a disaccharide at position seven to give flavanone glycosides.-List of flavanones:* Butin* Eriodictyol* Hesperetin* Hesperidin* Homoeriodictyol* Isosakuranetin* Naringenin...
s, and quercetin
Quercetin
Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...
glucosides, but with different kinetics. The least well-absorbed phenols are the proanthocyanidins, galloylated tea catechins, and anthocyanin
Anthocyanin
Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...
s.
Analytical methods
Studies on evaluating antioxidant capacity can used electrochemical methods.Detection can be made by recombinant luminescent bacterial sensor
Sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
s.
Genetic analysis
The phenolic metabolic pahways and enzymes can be studied by mean of transgenesisTransgenesis
thumb|300px|right|A diagram comparing the genetic changes achieved through conventional plant breeding, transgenesis and cisgenesisTransgenesis is the process of introducing an exogenous gene – called a transgene – into a living organism so that the organism will exhibit a new property and transmit...
of genes. The Arabidopsis
Arabidopsis thaliana
Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...
regulatory gene Production of Anthocyanin
Anthocyanin
Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to pH...
Pigment 1 (AtPAP1) can be expressed in other plant species.
See also
- Natural phenols and polyphenols in wine
- Natural phenols and polyphenols in tea
External links
Databases
- phenol-explorer.eu a database dedicated to phenolics found in food by Augustin Scalbert, INRA Clermont-Ferrand, Unité de Nutrition Humaine (Human food unit)
- FlavonoidViewer.jp (Japanese, English), a database on flavonoids by Arita Group (Univ of Tokyo, RIKEN Plant Science Center, and Keio Univ), Nishioka Group (Kyoto and Keio Univ) and Kanaya Group (NAIST)
- ChEMBLdb, a database of bioactive drug-like small molecules by the European Bioinformatics Institute