Diterpenes are a class of terpenes composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being a primary intermediate. Diterpenes form the basis for biologically important compounds such as retinol, retinal, and phytol. They are known to be antimicrobial and anti-inflammatory. [1] [2]
As with most terpenes a huge number of potential structures exists, which may be broadly divided according to the number of rings present.
| Number of rings | Examples |
|---|---|
| 0 | Phytane |
| 1 | Cembrene A |
| 2 | Sclarene, Labdane |
| 3 | Abietane, Taxadiene |
| 4 | Stemarene, Stemodene |
Diterpenes are derived from the addition of one IPP unit to FPP to form geranylgeranyl pyrophosphate (GGPP). From GGPP, structural diversity is achieved mainly by two classes of enzymes; the diterpene synthases and cytochromes P450. Several diterpenes are produced by plants and cyanobacteria. GGPP is also the precursor for the synthesis of the phytane by the action of the enzyme geranylgeranyl reductase. This compound is used for the biosynthesis of tocopherols and the phytyl functional group is used in the formation of chlorophyll a, ubiquinones, plastoquinone and phylloquinone. [3]
Diterpenes are formally defined as being hydrocarbons and thus contain no heteroatoms. Functionalized structures should instead be called diterpenoids[ citation needed ], although in scientific literature the two terms are often used interchangeably. Although a wide range of terpene structures exist, few of them are biologically significant; by contrast, diterpenoids possess a rich pharmacology and include important compounds such as retinol and phytol. The principal psychoactive constituent of the cannabis plant, used for treatment of anorexia associated with AIDS as well as nausea and vomiting associated with cancer chemotherapy, Delta(9)-tetrahydrocannabinol is a diterpenoid, a cannabinoid receptor agonist and an epitope. [4]
Taxanes are class of diterpenoids featuring a taxadiene core. They are produced by plants of the genus Taxus (yew trees) and are widely used as chemotherapy agents. [5]
The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes", terpenoids contain additional functional groups, usually containing oxygen. When combined with the hydrocarbon terpenes, terpenoids comprise about 80,000 compounds. They are the largest class of plant secondary metabolites, representing about 60% of known natural products. Many terpenoids have substantial pharmacological bioactivity and are therefore of interest to medicinal chemists.
Terpenes are a class of natural products consisting of compounds with the formula (C5H8)n for n ≥ 2. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes are further classified by the number of carbons: monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), as examples. The terpene alpha-pinene is a major component of the common solvent, turpentine.
Bilobalide is a biologically active terpenic trilactone present in Ginkgo biloba.
Ginkgolides are biologically active terpenic lactones present in Ginkgo biloba. They are diterpenoids with 20-carbon skeletons, which are biosynthesized from geranylgeranyl pyrophosphate.
Geranyl pyrophosphate (GPP), also known as geranyl diphosphate (GDP), is the pyrophosphate ester of the terpenoid geraniol. Its salts are colorless. It is a precursor to many natural products.
Farnesyl pyrophosphate (FPP), also known as farnesyl diphosphate (FDP), is an intermediate in the biosynthesis of terpenes and terpenoids such as sterols and carotenoids. It is also used in the synthesis of CoQ, as well as dehydrodolichol diphosphate.
Geranylgeranyl pyrophosphate is an intermediate in the biosynthesis of diterpenes and diterpenoids. It is also the precursor to carotenoids, gibberellins, tocopherols, and chlorophylls.
Sesquiterpenes are a class of terpenes that consist of three isoprene units and often have the molecular formula C15H25. Like monoterpenes, sesquiterpenes may be cyclic or contain rings, including many unique combinations. Biochemical modifications such as oxidation or rearrangement produce the related sesquiterpenoids.
Monoterpenes are a class of terpenes that consist of two isoprene units and have the molecular formula C10H16. Monoterpenes may be linear (acyclic) or contain rings (monocyclic and bicyclic). Modified terpenes, such as those containing oxygen functionality or missing a methyl group, are called monoterpenoids. Monoterpenes and monoterpenoids are diverse. They have relevance to the pharmaceutical, cosmetic, agricultural, and food industries.
Tetraterpenes are terpenes consisting of eight isoprene units and have the molecular formula C40H64. Tetraterpenoids (including many carotenoids) are tetraterpenes that have been chemically modified, as indicated by the presence of oxygen-containing functional groups.
Triterpenes are a class of terpenes composed of six isoprene units with the molecular formula C30H48; they may also be thought of as consisting of three terpene units. Animals, plants and fungi all produce triterpenes, including squalene, the precursor to all steroids.
Terpineol is any of four isomeric monoterpenoids. Terpenoids are terpene that are modified by the addition of a functional group, in this case, an alcohol. Terpineols have been isolated from a variety of sources such as cardamom, cajuput oil, pine oil, and petitgrain oil. Four isomers exist: α-, β-, γ-terpineol, and terpinen-4-ol. β- and γ-terpineol differ only by the location of the double bond. Terpineol is usually a mixture of these isomers with α-terpineol as the major constituent.
Fusicoccins are organic compounds produced by a fungus. It has detrimental effect on plants and causes their death.
Steviol is a diterpene first isolated from the plant Stevia rebaudiana in 1931. Its chemical structure was not fully elucidated until 1960.
In enzymology, bornyl diphosphate synthase (BPPS) (EC 5.5.1.8) is an enzyme that catalyzes the chemical reaction
In enzymology, an ent-copalyl diphosphate synthase is an enzyme that catalyzes the chemical reaction:
Levopimaric acid is an abietane-type of diterpene resin acid. It is a major constituent of pine oleoresin with the chemical formula of C20H30O2. In general, the abietene types of diterpene resin acid have various biological activities, such as antibacterial, cardiovascular and antioxidant. Levopimaric acid accounts for about 18 to 25% of pine oleoresin. The production of oleoresin by conifer species is an important component of the defense response against insect attack and fungal pathogen infection.
Pseudopterosin A is a diterpene glycoside isolated from the gorgonian sea whip Antillogorgia elisabethae, found in the Bahamas and Florida Keys. Pseudopterosins A-D, which differ in the degree of acetylation at the sugar ring, were first isolated and reported in 1986. There are at least 25 unique diterpenes isolated from this species of marine animal. Samples of P. elisabethae from the Bahamas are found to have higher concentrations of pseudopterosins than populations from the Florida Keys, which have a greater diversity in diterpene structures.
Incensole is a C20 diterpene alcohol and biomarker for some plants of the Boswellia genus. It, along with its acetate ester incensole acetate, is an abundant component of frankincense, the resin collected from Boswellia trees. Incensole is used archaeologically to assist in identifying trade routes and distinguishing the identity of frankincense from other resins which may have been used together in incense and other salves. Incensole has also been deemed to be an active component in medicinal frankincense.
Sugiol is a phenolic abietane derivative of ferruginol and can be used as a biomarker for specific families of conifers. The presence of sugiol can be used to identify the Cupressaceae s.1., podocarpaceae, and Araucaraiaceae families of conifers. The polar terpenoids are among the most resistant molecules to degradation besides n-alkanes and fatty acids, affording them high viability as biomarkers due to their longevity in the sedimentary record. Significant amounts of sugiol has been detected in fossil wood dated to the Eocene and Miocene periods, as well as a sample of Protopodocarpoxylon dated to the middle Jurassic.
