Totarol
Encyclopedia
Totarol is a a meroterpene natural phenol. It is naturally produced phenolic diterpene
that is bioactive as (+)-totarol. It was first isolated by McDowell and Esterfield from the heartwood of Podocarpus totara
, a yew tree found in New Zealand
. Podocarpus totara was investigated for unique molecules due to the tree’s increased resistance to rotting
. Recent studies have confirmed (+)-totarol’s unique antimicrobial
and therapeutic
properties. Consequently, (+)-totarol is a promising candidate for a new source of drugs and has been the goal of numerous syntheses.
and Cupressaceae
, with the majority found in the Podocarpus family of the Podocarpaceae and the Cupressoideae subfamily of the Cupressaceae.
Outside Podocarpus and Cupressoideae, (+)-totarol is rarely found in the plant kingdom. However, (+)-totarol has recently been isolated in Rosmary officinalis. The gymnosperm
s that contain (+)-totarol are distributed worldwide but are concentrated in North America, the far-south regions of South America
, East Asia
and East Africa
.
bacteria, nematode
s, parasitic protozoans
, crustaceous foulers (Table 1). In addition to inhibiting microorganisms by itself, (+)-totarol exhibits inhibitory synergy with currently used antimicrobial drugs: (+)-totarol potentiates isonicotinic acid hydrazide against various Mycobactiera.; methicillin against Mycobacterium tuberculosis
and Staphylococcus aureus
; and anacardic acid and erythromycin against Staphylococcus aureus. In nature, (+)-totarol is a key player in gymnosperm’s defense against harmful microbes: gymnosperms that produce (+)-totarol are increasingly resistant to rotting.
Table 1. Antibacterial activity of (+)-totarol against microorganisms
via creation of penicillin binding protein
2’ (PBP2’), (+)-totarol may inhibit the synthesis of PBP2’. (+)-Totarol may inhibit effluxing Staphylococcus aureus strains through inhibition of MsrA, although it is unclear if MsrA is an efflux pump. (+)-Totarol may also gain its antibacterial properties by inhibiting bacterial respiratory transport but this is very unlikely because (+)-totarol is also effective against anaerobic organism
s. Recently (+)-totarol was also hypothesized to inhibit gram-positive and acid-fast bacteria via inhibition of FtsZ protein, which forms the Z-ring, a polymer necessary for efficient bacterial cell cytokinesis
.
(+)-Totarol may also function by disrupting the structural integrity of the phospholipid bilayer
of bacteria by weakening Van der Waals interactions with its phenolic group, which also results in bacterial cells unable to synthesize ATP. Motivation for (+)-totarol functioning via disruption of membrane structure is due to its high phospholipid/water partition coefficient. However, (+)-totarol’s partitioning capability was only observed at concentrations 10 to 100 fold higher than required for antibacterial activity. Thus it is unlikely that (+)-totarol is an uncoupler of bacterial respiration at the low levels observed in antimicrobial studies.
medicines for treatment of fever
s, asthma
, cough
s, cholera
, distemper
, chest complaints and venereal disease dates back to over 100 years. (+)-Totarol has anti-cancer capabilities: totarol decreases the plasma levels of estrogens and can also effectively reduce pathogenic hepatic cells. (+)-Totarol’s anti-cancer activity is hypothesized to be due to the natural product’s ability to form an o-quinone methide in vivo. (+)-Totarol also prevents cells from undergoing oxidative stress by acting as a hydrogen donor to peroxy radicals or reacting with other peroxy radicals to terminate undesirable radical reactions.. Lastly, (+)-totarol serves as a therapeutic for individuals with bad heart health by inhibiting cholesterol absorption and possibly stimulating cholesterol catabolism or excretion.
Despite (+)-totarol’s impressive antimicrobial and therapeutic potential, its commercial usage is currently limited to cosmetic purposes. For (+)-totarol to be used clinically, its mode of action needs to be clearly defined.
properties not possessed by (+)-totarol. Consequently, gymnosperms that produce (+)-totarol and nagilactones are able to defend themselves against antibacterial and antifungal organisms.
The biosynthesis of (+)-totarol was difficult to determine. The main reason for the challenge in determining how the secondary metabolite is produced is because (+)-totarol does not follow the isoprene rule: the isopropyl group of (+)-totarol is in the “wrong” place at C14. Initially, it was hypothesized that (+)-totarol and the “normal” diterpene ferruginol, also found in Podocarpaceae, were derived by a precursor 2 that would be dehydrated and have its isopropyl group migrate at the point of photosynthesis to produce (+)-totarol 1 and ferruginol 3 (Scheme 1). This hypothesis was motivated by the well known santonin-desmotroposantonin rearrangement of steroid dienones into aromatic compounds. It is now accepted that (+)-totarol is synthesized biologically from ferruginol. Geranyl geranyl pyrophosphate 4 undergoes typical diterpene cyclization to form (-)-abietadiene 5, which is oxidized at to form ferruginol 3, which proceeds through a spiro intermediate to form (+)-totarol (Scheme 2).
9 via hydrogenation
followed by cyclization
with polyphosphoric acid
. 9 was subsequently converted to 10 and another ketone that were inseparable by chromatography
. The synthesis was finalized by treatment of with N-Bromosuccinimide
followed by debromination to yield (±)-totarol. The main downfall of this synthesis was that in multiple steps, complete conversion of reactant to products was not observed and undesirable side products were often not separable by chromatography. However, since this was the first total synthesis of (+)-totarol, it is notable.
A more recent organic synthesis of (+)-totarol was achieved by utilizing 14, a lamdane diterpene named zamoranic acid (Scheme 5). The addition of the isopropyl group in the chemical synthesis was achieved with complete steroselectivity. Acetylation to yield 15 required high temperatures due to the steric hindrance of the isopropyl group. Cis-hydroxylation followed by cleavage with H5IO6 yielded a diol that was acylated in pyridine and oxidized to give 16. The key step in the synthesis was the cyclization of ring C: 16 was treated with SmI2 to yield totarane disatereomers which were separated by column chromatography. The desired diastereomer was treated with p-TsOH in benzene to yield 17. The synthesis was completed by a pinacole rearrangement followed by a halogenation-dehydrogenation sequence and subsequent bromination to yield 18 and ring aromatization with elimination via a lithium complex.
(+)-Totarol has been found on the posterior tibia of Frieseomelita silvestrii languida, a species of stingless bees from Brazil. Frieseomelita silvestrii languida collect resin to create a protective barrier around the opening of their nest to ward of insects from settling near the nest's entrance. The presence of (+)-totarol can aid in the determination of this bee species.
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...
that is bioactive as (+)-totarol. It was first isolated by McDowell and Esterfield from the heartwood of Podocarpus totara
Podocarpus totara
Podocarpus totara is a species of podocarp tree endemic to New Zealand. It grows throughout the North Island and northeastern South Island in lowland, montane and lower subalpine forest at elevations of up to 600 m.-Description:...
, a yew tree found in New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. Podocarpus totara was investigated for unique molecules due to the tree’s increased resistance to rotting
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
. Recent studies have confirmed (+)-totarol’s unique antimicrobial
Antimicrobial
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...
and therapeutic
Therapy
This is a list of types of therapy .* Adventure therapy* Animal-assisted therapy* Aquatic therapy* Aromatherapy* Art and dementia* Art therapy* Authentic Movement* Behavioral therapy* Bibliotherapy* Buteyko Method* Chemotherapy...
properties. Consequently, (+)-totarol is a promising candidate for a new source of drugs and has been the goal of numerous syntheses.
Occurrence
Although totarol was first isolated in Podocarpus totara, (+)-totarol has also been identified in numerous other species of PodocarpaceaePodocarpaceae
Podocarpaceae is a large family of mainly Southern Hemisphere conifers, comprising about 156 species of evergreen trees and shrubs. It contains 19 genera if Phyllocladus is included and if Manoao and Sundacarpus are recognized....
and Cupressaceae
Cupressaceae
The Cupressaceae or cypress family is a conifer family with worldwide distribution. The family includes 27 to 30 genera , which include the junipers and redwoods, with about 130-140 species in total. They are monoecious, subdioecious or dioecious trees and shrubs from 1-116 m tall...
, with the majority found in the Podocarpus family of the Podocarpaceae and the Cupressoideae subfamily of the Cupressaceae.
Outside Podocarpus and Cupressoideae, (+)-totarol is rarely found in the plant kingdom. However, (+)-totarol has recently been isolated in Rosmary officinalis. The gymnosperm
Gymnosperm
The gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...
s that contain (+)-totarol are distributed worldwide but are concentrated in North America, the far-south regions of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, East Asia
East Asia
East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...
and East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
.
Antimicrobial activity
(+)-Totarol motivates research in drug discovery due to its ability to inhibit numerous microorganisms. (+)-Totarol exhibits antimicrobial properties in numerous species including gram-positive bacteria, acid-fastAcid-fast
Acid-fastness is a physical property of certain bacteria, specifically their resistance to decolorization by acids during staining procedures.Acid-fast organisms are difficult to characterize using standard microbiological techniques Acid-fastness is a physical property of certain bacteria,...
bacteria, nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s, parasitic protozoans
Protozoan infection
Protozoan infections are parasitic diseases organisms formerly classified in the Kingdom Protozoa. They include organisms classified in Amoebozoa, Excavata, and Chromalveolata....
, crustaceous foulers (Table 1). In addition to inhibiting microorganisms by itself, (+)-totarol exhibits inhibitory synergy with currently used antimicrobial drugs: (+)-totarol potentiates isonicotinic acid hydrazide against various Mycobactiera.; methicillin against Mycobacterium tuberculosis
Mycobacterium tuberculosis
Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...
and Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
; and anacardic acid and erythromycin against Staphylococcus aureus. In nature, (+)-totarol is a key player in gymnosperm’s defense against harmful microbes: gymnosperms that produce (+)-totarol are increasingly resistant to rotting.
Table 1. Antibacterial activity of (+)-totarol against microorganisms
| Microorganism | MIC (μg/ml) | IC50(μg/ml) |
|---|---|---|
| Artemia salina | |
|
| Bacterium ammoniagenes | |
|
| Bacillus subtilis | |
|
| Caenorhabditis elegans | |
|
| Enterococcus faecalis | |
|
| Klebsiella pneumoniae | |
|
| Mycobacterium aurum | |
|
| Mycobacterium fortuitum | |
|
| Mycobacterium phlei | |
|
| Mycobacterium smegmatis | |
|
| Mycobacterium tuberculosis H37Rv | |
|
| Leishmania donovani | |
|
| Proprionibacterium acnes | |
|
| Staphylococcus aureus ATCC 12598 | |
|
| Staphylococcus aureus ATCC 33591 | |
|
| Staphylococcus aureus ATCC 11632 | |
|
| Streptococcus mutans | |
|
| Streptococcus pneumoniae | |
|
Mechanism of antimicrobial inhibition
Although (+)-totarol exhibits antimicrobial properties, the mode of action is unclear and various methods of inhibitory action have been proposed. In Staphylococcus aureus strains resistant to penicillinPenicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....
via creation of penicillin binding protein
Penicillin binding proteins
Penicillin-binding proteins are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria; the name just reflects the way by which the protein was discovered...
2’ (PBP2’), (+)-totarol may inhibit the synthesis of PBP2’. (+)-Totarol may inhibit effluxing Staphylococcus aureus strains through inhibition of MsrA, although it is unclear if MsrA is an efflux pump. (+)-Totarol may also gain its antibacterial properties by inhibiting bacterial respiratory transport but this is very unlikely because (+)-totarol is also effective against anaerobic organism
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
s. Recently (+)-totarol was also hypothesized to inhibit gram-positive and acid-fast bacteria via inhibition of FtsZ protein, which forms the Z-ring, a polymer necessary for efficient bacterial cell cytokinesis
Cytokinesis
Cytokinesis is the process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. It usually initiates during the late stages of mitosis, and sometimes meiosis, splitting a binucleate cell in two, to ensure that chromosome number is maintained from one generation...
.
(+)-Totarol may also function by disrupting the structural integrity of the phospholipid bilayer
Lipid bilayer
The lipid bilayer is a thin membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around cells. The cell membrane of almost all living organisms and many viruses are made of a lipid bilayer, as are the membranes surrounding the cell nucleus...
of bacteria by weakening Van der Waals interactions with its phenolic group, which also results in bacterial cells unable to synthesize ATP. Motivation for (+)-totarol functioning via disruption of membrane structure is due to its high phospholipid/water partition coefficient. However, (+)-totarol’s partitioning capability was only observed at concentrations 10 to 100 fold higher than required for antibacterial activity. Thus it is unlikely that (+)-totarol is an uncoupler of bacterial respiration at the low levels observed in antimicrobial studies.
Therapeutic properties
In addition to antimicrobial properties, (+)-totarol has therapeutic properties. The use of Podocarpus totara extract in MaoriMaori culture
Māori culture is the culture of the Māori of New Zealand, an Eastern Polynesian people, and forms a distinctive part of New Zealand culture. Within the Māori community, and to a lesser extent throughout New Zealand as a whole, the word Māoritanga is often used as an approximate synonym for Māori...
medicines for treatment of fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
s, asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
, cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
s, cholera
Cholera
Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. The main symptoms are profuse watery diarrhea and vomiting. Transmission occurs primarily by drinking or eating water or food that has been contaminated by the diarrhea of an infected person or the feces...
, distemper
Distemper
Distemper may refer to:*A viral infection**Canine distemper, a disease of dogs**Feline distemper, a disease of cats**Phocine distemper, a disease of seals*A bacterial infection**Equine distemper, or Strangles, a bacterial infection of the horse...
, chest complaints and venereal disease dates back to over 100 years. (+)-Totarol has anti-cancer capabilities: totarol decreases the plasma levels of estrogens and can also effectively reduce pathogenic hepatic cells. (+)-Totarol’s anti-cancer activity is hypothesized to be due to the natural product’s ability to form an o-quinone methide in vivo. (+)-Totarol also prevents cells from undergoing oxidative stress by acting as a hydrogen donor to peroxy radicals or reacting with other peroxy radicals to terminate undesirable radical reactions.. Lastly, (+)-totarol serves as a therapeutic for individuals with bad heart health by inhibiting cholesterol absorption and possibly stimulating cholesterol catabolism or excretion.
Despite (+)-totarol’s impressive antimicrobial and therapeutic potential, its commercial usage is currently limited to cosmetic purposes. For (+)-totarol to be used clinically, its mode of action needs to be clearly defined.
Biosynthesis
(+)-Totarol is a precursor to the formation of nagilactones that possess antifungalAntifungal drug
An antifungal medication is a medication used to treat fungal infections such as athlete's foot, ringworm, candidiasis , serious systemic infections such as cryptococcal meningitis, and others...
properties not possessed by (+)-totarol. Consequently, gymnosperms that produce (+)-totarol and nagilactones are able to defend themselves against antibacterial and antifungal organisms.
The biosynthesis of (+)-totarol was difficult to determine. The main reason for the challenge in determining how the secondary metabolite is produced is because (+)-totarol does not follow the isoprene rule: the isopropyl group of (+)-totarol is in the “wrong” place at C14. Initially, it was hypothesized that (+)-totarol and the “normal” diterpene ferruginol, also found in Podocarpaceae, were derived by a precursor 2 that would be dehydrated and have its isopropyl group migrate at the point of photosynthesis to produce (+)-totarol 1 and ferruginol 3 (Scheme 1). This hypothesis was motivated by the well known santonin-desmotroposantonin rearrangement of steroid dienones into aromatic compounds. It is now accepted that (+)-totarol is synthesized biologically from ferruginol. Geranyl geranyl pyrophosphate 4 undergoes typical diterpene cyclization to form (-)-abietadiene 5, which is oxidized at to form ferruginol 3, which proceeds through a spiro intermediate to form (+)-totarol (Scheme 2).
Synthesis
(+)-Totarol has been the subject of numerous syntheses. The first total synthesis of totarol (Scheme 3) utilized 6 and the 7 Grignard to yield 8 which was converted to the corresponding ketoneKetone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
9 via hydrogenation
Hydrogenation
Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...
followed by cyclization
Cyclic compound
In chemistry, a cyclic compound is a compound in which a series of atoms is connected to form a loop or ring.While the vast majority of cyclic compounds are organic, a few inorganic substances form cyclic compounds as well, including sulfur, silanes, phosphanes, phosphoric acid, and triboric acid. ...
with polyphosphoric acid
Phosphoric acids and Phosphates
There are various kinds of phosphoric acids and phosphates. Of the many phosphorus oxoacids, the phosphoric acids constitute the largest and most diverse group. The simplest phosphoric acid series begins with monophosphoric acid, continues with many oligophosphoric acids such as diphosphoric acid...
. 9 was subsequently converted to 10 and another ketone that were inseparable by chromatography
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
. The synthesis was finalized by treatment of with N-Bromosuccinimide
N-Bromosuccinimide
N-Bromosuccinimide or NBS is a chemical reagent which is used in radical substitution and electrophilic addition reactions in organic chemistry. NBS can be considered a convenient source of cationic bromine.-Preparation:...
followed by debromination to yield (±)-totarol. The main downfall of this synthesis was that in multiple steps, complete conversion of reactant to products was not observed and undesirable side products were often not separable by chromatography. However, since this was the first total synthesis of (+)-totarol, it is notable.
Total enantioselective synthesis
The first total enatioselective synthesis of (+)-totarol was achieved in 1979 (Scheme 4). The key step in the synthesis is the formation of the A and C ring in 13 via a Wittig reaction between 11 and 12. This same cyclization can also be achieved via a Friedel-Crafts alkylation and cyclization. Subsequent hydrogenation of 13 followed by intramolecular cyclization with aluminium chloride forms the B ring and (+)-totarylmethyl ether which is demethylated by boron tribromide to yield (+)-totarol.A more recent organic synthesis of (+)-totarol was achieved by utilizing 14, a lamdane diterpene named zamoranic acid (Scheme 5). The addition of the isopropyl group in the chemical synthesis was achieved with complete steroselectivity. Acetylation to yield 15 required high temperatures due to the steric hindrance of the isopropyl group. Cis-hydroxylation followed by cleavage with H5IO6 yielded a diol that was acylated in pyridine and oxidized to give 16. The key step in the synthesis was the cyclization of ring C: 16 was treated with SmI2 to yield totarane disatereomers which were separated by column chromatography. The desired diastereomer was treated with p-TsOH in benzene to yield 17. The synthesis was completed by a pinacole rearrangement followed by a halogenation-dehydrogenation sequence and subsequent bromination to yield 18 and ring aromatization with elimination via a lithium complex.
Total chemoenzymatic synthesis
Chemoenzymatic synthesis of (+)-totarol has also been achieved with high yield (41.8%) (Scheme 6). A racemic beta-keto ester 19 undergoes lipase-assisted resolution to yield chiral alcohol 20. Treatment of 20 with 10% HCl and p-TsOH gives αβ-unsaturated ketone 21. A Michael addition with the anion obtained from the reaction of methyl 5-methyl-3-oxohexanoate 13 with NaOMe gives a 2:1 diastereomeric mixture of 22 which is hydrolyzed to yield 23 which is brominated and debrominated to yield (+)-totarol.Other uses
(+)-Totarol may also be used as an indicator for the quality of juniper berry based spirits. Juniper berries that contain diterpenoids including (+)-totarol are used for the aromatization and production of some gins. Consequently, (+)-totarol can aid in the characterization of different types of gin or commercial brands, vouching for the authenticity and quality of the product.(+)-Totarol has been found on the posterior tibia of Frieseomelita silvestrii languida, a species of stingless bees from Brazil. Frieseomelita silvestrii languida collect resin to create a protective barrier around the opening of their nest to ward of insects from settling near the nest's entrance. The presence of (+)-totarol can aid in the determination of this bee species.