Glucoside
Encyclopedia
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...
that is derived from glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
by purely chemical means, or decomposed by fermentation
Fermentation (biochemistry)
Fermentation is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound. In contrast, respiration is where electrons are donated to an exogenous electron acceptor, such as oxygen,...
or enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s.
The name was originally given to plant products of this nature, in which the other part of the molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
was, in the greater number of cases, an aromatic aldehydic or 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 compound (exceptions are sinigrin
Sinigrin
Sinigrin is a glucosinolate that belongs to the family of glucosides found in some plants of the Brassicaceae family such as Brussels sprouts, broccoli, and the seeds of black mustard to name but a few...
and jalapin or scammonin). It has now been extended to include synthetic 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"...
s, such as those obtained by acting on alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
ic glucose solutions with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
, and also the polysaccharoses, e.g. cane sugar, which appear to be ethers also. Although glucose is the most common sugar present in glucosides, many are known which yield rhamnose
Rhamnose
Rhamnose is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose occurs in nature in its L-form as L-rhamnose . This is unusual, since most of the naturally occurring sugars are in D-form...
or iso-dulcite; these may be termed pentosides. Much attention has been given to the non-sugar parts (aglyca) of the molecules; the constitutions of many have been determined, and the compounds synthesized; and in some cases the preparation of the synthetic glucoside effected.
The simplest glucosides are the alkyl ethers which have been obtained by reacting hydrochloric acid on alcoholic glucose solutions. A better method of preparation is to dissolve solid anhydrous glucose in methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
containing hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
. A mixture of alpha- and beta-methylglucoside results.
Classification of the glucosides is a matter of some intricacy. One method based on the chemical constitution of the non-glucose part of the molecules has been proposed that posits four groups: (I) alkyl derivatives, (2) benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
derivatives, (3) styrolene derivatives, and (4) anthracene
Anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings. It is a component of coal-tar. Anthracene is used in the production of the red dye alizarin and other dyes...
derivatives. A group may also be constructed to include the cyanogenic glucosides, i.e. those containing prussic acid. Alternate classifications follow a botanical classification, which has several advantages; in particular, plants of allied genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
contain similar compounds. In this article the chemical classification will be followed, and only the more important compounds will be discussed herein.
Ethylene Derivatives
These are generally mustard oils, which are characterized by a burning taste; their principal occurrence is in mustardMustard seed
Mustard seeds are the small round seeds of various mustard plants. The seeds are usually about 1 or 2 mm in diameter. Mustard seeds may be colored from yellowish white to black. They are important spices in many regional foods. The seeds can come from three different plants: black mustard , brown...
and Tropaeolum seeds. Sinigrin
Sinigrin
Sinigrin is a glucosinolate that belongs to the family of glucosides found in some plants of the Brassicaceae family such as Brussels sprouts, broccoli, and the seeds of black mustard to name but a few...
, or the potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
of inyronic acid not only occurs in mustard seed but also in black pepper
Black pepper
Black pepper is a flowering vine in the family Piperaceae, cultivated for its fruit, which is usually dried and used as a spice and seasoning. The fruit, known as a peppercorn when dried, is approximately in diameter, dark red when fully mature, and, like all drupes, contains a single seed...
and in horseradish
Horseradish
Horseradish is a perennial plant of the Brassicaceae family, which also includes mustard, wasabi, broccoli, and cabbages. The plant is probably native to south eastern Europe and the Arab World , but is popular around the world today...
root. Hydrolysis with baryta, or decomposition by the ferment myrosin, gives glucose, allyl mustard oil and potassium hydrogen sulfate
Potassium hydrogen sulfate
Potassium bisulfate is the potassium salt of bisulfate anion, with the molecular formula . This compound is commonly used in the conversion of tartrates to bitartrates in wine. Potassium bisulfate is also used as a disintegrating agent in analytical chemistry....
. Sinalbin
Sinalbin
Sinalbin is a glucosinolate found in the seeds of white mustard, Sinapis alba, and in many wild plant species. In contrast to mustard from black mustard seeds which contain sinigrin, mustard from white mustard seeds has only a weakly pungent taste.The less sharp taste is because the mustard oil...
occurs in white pepper; it decomposes to the mustard oil, glucose and sinapin, a compound of choline
Choline
Choline is a water-soluble essential nutrient. It is usually grouped within the B-complex vitamins. Choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation....
and sinapic acid. Jalapin or scammonin occurs in scammony
Scammony
Scammony is a bindweed native to the countries of the eastern part of the Mediterranean basin; it grows in bushy waste places, from Syria in the south to the Crimea in the north, its range extending westward to the Greek islands, but not to northern Africa or Italy.It is a twining perennial,...
; it hydrolyses to glucose and jalapinolic acid.
Benzene Derivatives
These are generally oxy and oxyaldehydic compounds.Benzoic acid derivatives
The benzoyl derivative cellotropin has been used for tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
. Populin, which occurs in the leaves and bark of Populus tremula, is benzoyl salicin. Benzoyl-beta-D-glucoside
Benzoyl-beta-D-glucoside
Benzoyl-beta-D-glucoside is a benzoyl glucoside, a natural substance that can be found in Pteris ensiformis....
is a compound found in Pteris ensiformis.
Phenol derivatives
There are a number of glucosides found in natural phenol
Natural phenol
Natural phenols, bioavailable phenols, plant phenolics, low molecular weight phenols or phenoloids are a class of natural products. They are small molecules containing one or more phenolic group. These molecules are smaller in size than polyphenols, containing less than 12 phenolic groups...
s and 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, as, for example, in the flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
s chemical family. Arbutin
Arbutin
Arbutin is both an ether and a glycoside; a glycosylated hydroquinone extracted from bearberry plant in the genus Arctostaphylos. It inhibits tyrosinase and thus prevents the formation of melanin. Arbutin is therefore used as a skin-lightening agent. Arbutin is found in wheat, and is concentrated...
, which occurs in bearberry
Bearberry
Bearberries are three species of dwarf shrubs in the genus Arctostaphylos. Unlike the other species of Arctostaphylos , they are adapted to Arctic and sub-Arctic climates, and have a circumpolar distribution in northern North America, Asia and Europe, one with a small highly disjunctive population...
along with methyl arbutin, hydrolyses to hydroquinone
Hydroquinone
Hydroquinone, also benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, having the chemical formula C6H42. Its chemical structure, shown in the table at right, has two hydroxyl groups bonded to a benzene ring in a para position. It is a white granular solid...
and glucose. Pharmacologically it acts as a urinary antiseptic
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...
and diuretic
Diuretic
A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...
; Salicin, also termed saligenin and glucose occurs in the willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
. The enzymes ptyalin and emulsin convert it into glucose and saligenin, ortho-oxybenzylalcohol. Oxidation gives the aldehyde helicin.
Styrolene Derivatives
This group contains a benzene and also an ethyleneEthylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...
group, being derived from styrolene. Coniferin
Coniferin
Coniferin is a glucoside of coniferyl alcohol. This white crystalline solid is a metabolite in conifers, serving as an intermediate in cell wall lignification, as well as having other biological roles....
, C16H22O8, occurs in the cambium of conifer wood. Emulsin converts it into glucose and coniferyl alcohol
Coniferyl alcohol
Coniferyl alcohol is an organic compound. This colourless crystalline solid is a phytochemical, one of the monolignols. It is synthethized via the phenylpropanoid biochemical pathway. When copolymerized with related aromatic compounds, coniferyl alcohol forms lignin or lignans...
, while oxidation gives glycovanillin, which yields with emulsin, glucose and vanillin
Vanillin
Vanillin is a phenolic aldehyde, an organic compound with the molecular formula C8H8O3. Its functional groups include aldehyde, ether, and phenol. It is the primary component of the extract of the vanilla bean. It is also found in Leptotes bicolor, roasted coffee and the Chinese red pine...
. Syringin
Syringin
Syringin is a natural chemical compound first isolated from the bark of lilac by Meillet in 1841. It has since been found to be distributed widely throughout many types of plants. Chemically, it is the glucoside of sinapyl alcohol....
, which occurs in the bark of Syringa vulgaris, is a methoxyconiferin. Phloridzus occurs in the root-bark of various 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,...
trees; it hydrolyses to glucose and phloretin, which is the phloroglucin 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...
of paraoxyhydratropic acid. It is related to the pentosides naringin
Naringin
Naringin is a flavanone glycoside. It is a major flavonoid in grapefruit and gives the grapefruit juice its bitter taste. It is metabolized to the flavanone naringenin in humans...
, C27H32O14, which hydrolyses to rhamnose and naringenin, the phioroglucin ester of para-oxycinnamic acid, and hesperidin, which hydrolyses to rhamnose
Rhamnose
Rhamnose is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose occurs in nature in its L-form as L-rhamnose . This is unusual, since most of the naturally occurring sugars are in D-form...
and hesperetin
Hesperetin
Hesperetin is a bioflavonoid and, to be more specific, a flavanone. Hesperidin is water-soluble due to the presence of the sugar part in its structure, so on ingestion it releases its aglycone, i.e, hesperetin....
, the phloroglucin ester of meta-oxy-para-methoxycinnamic acid or isoferulic acid, C10H10O4.
- AesculinAesculinAesculin, also rendered Æsculin or Esculin, is a glucoside that naturally occurs in the horse chestnut , California Buckeye and in daphnin ....
(C21H24O13), occurring in horse-chestnutHorse-chestnutHorse chestnut may refer to:*Horse-chestnut or Aesculus hippocastanum, a species of large deciduous tree**Horse chestnuts, Eurasian species of the genus Aesculus*Horse Chestnut , a South African Thoroughbred racehorse...
and California buckeye, and daphnin, occurring in Daphne alpina, are isomerIsomerIn chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
ic; the former hydrolyses to glucose and aesculetin (C9H6O4 — 6,7-dihydroxycoumarin), the latter to glucose and daphnetin (7,8-dihydroxycoumarin). - Fraxin, occurring in Fraxinus excelsior, and with aesculin, hydrolyses to glucose and fraxetin, 7,8-dihydroxy-6-methoxycoumarin.
- Flavone or benzo-7-pyrone derivatives are numerous; in many cases they (or the non-sugar part of the molecule) are vegetable dyes.
- QuercitrinQuercitrinQuercitrin is a glycoside formed from the flavonoid quercetin and the deoxy sugar rhamnose. It is a constituent of the dye quercitron. It can be found in Tartary buckwheat ....
is a yellow dyestuff found in Quercus velutina; it hydrolyses to rhamnoseRhamnoseRhamnose is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose occurs in nature in its L-form as L-rhamnose . This is unusual, since most of the naturally occurring sugars are in D-form...
and quercetin, a dioxy-~3-phenyl-trioxybenzoy-pyrone. - RhamnetinRhamnetinRhamnetin is an O-methylated flavonol, a type of chemical compound. It can be isolated from cloves.The structure of the molecule has been discovered by Austrian chemist Josef Herzig ....
, a splitting product of the glucosides of Rhamnus, is monomethyl quercetin; fisetinFisetinFisetin 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...
, from Rhus cotinus, is monoxyquercetin; chrysinChrysinChrysin is a naturally occurring flavone chemically extracted from the blue passion flower . Honeycomb also contains small amounts. It is also reported in Oroxylum indicum or Indian trumpetflower.-Aromatase inhibition:...
is phenyl-dioxybenzo-y-pyrone. - Saponarin, a glucoside found in Saponaria officinalis, is a related compound.
- Strophanthin is the name given to two different compounds, g-strophanthin (ouabainOuabainOuabain which is also named g-strophanthin, is a poisonous cardiac glycoside.-Sources:Ouabain is found in the ripe seeds of African plants Strophanthus gratus and the bark of Acokanthera ouabaio.-Function:...
) obtained from Strophanthus gratus and k-strophanthin from Stroph. kombé.
Anthracene Derivatives
These are generally substituted anthraquinones; many have medicinal applications, being used as purgatives, while one, ruberythric acid, yields the valuable dyestuff madder, the base of which is alizarin. Chrysophanic acid, a dioxymethylanthraquinone, occurs in rhubarb, which also contains emodinEmodin
Emodin is a purgative resin, 6-methyl-1,3,8-trihydroxyanthraquinone, from rhubarb, the buckthorn and Japanese Knotweed...
, a trioxymethylanthraquinone; this substance occurs in combination with rhamnose in Frangula bark.
The most important cyanogenetic glucoside is amygdalin
Amygdalin
Amygdalin , C20H27NO11, is a glycoside initially isolated from the seeds of the tree Prunus dulcis, also known as bitter almonds, by Pierre-Jean Robiquet...
, which occurs in bitter almonds. The enzyme maltase
Maltase
Maltase is an enzyme that breaks down the disaccharide maltose. Maltase is an enzyme that catalyzes the hydrolysis of the disaccharide maltose to the simple sugar glucose. This enzyme is found in plants, bacteria, and yeast. Then there is what is called Acid maltase deficiency...
decomposes it into glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
and mandelic nitrile glucoside; the latter is broken down by emulsin into glucose, benzaldehyde
Benzaldehyde
Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...
and prussic acid. Emulsin also decomposes amygdalin
Amygdalin
Amygdalin , C20H27NO11, is a glycoside initially isolated from the seeds of the tree Prunus dulcis, also known as bitter almonds, by Pierre-Jean Robiquet...
directly into these compounds without the intermediate formation of mandelic nitrile glucoside.
Several other glucosides of this nature have been isolated. The saponin
Saponin
Saponins are a class of chemical compounds, one of many secondary metabolites found in natural sources, with saponins found in particular abundance in various plant species...
s are a group of substances characterized by forming a lather with water; they occur in soap-bark. Mention may also be made of indican
Indican
Indican is a colourless organic compound, soluble in water, naturally occurring in Indigofera plants. It is a precursor of indigo dye.-Chemical reactions:Common and significant reactions involving indican are as follows:...
, the glucoside of the indigo
Indigo
Indigo is a color named after the purple dye derived from the plant Indigofera tinctoria and related species. The color is placed on the electromagnetic spectrum between about 420 and 450 nm in wavelength, placing it between blue and violet...
plant; this is hydrolysed by the indigo
Indigo
Indigo is a color named after the purple dye derived from the plant Indigofera tinctoria and related species. The color is placed on the electromagnetic spectrum between about 420 and 450 nm in wavelength, placing it between blue and violet...
ferment, indimulsiri, to indoxyl
Indoxyl
In chemistry, indoxyl is a nitrogenous substance with the chemical formula: C8H7NO. Indoxyl is isomeric with oxindol and is obtained as an oily liquid....
and indiglucin.