Diterpenes are a class of chemical compounds composed of four

isoprene Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an unsaturated hydrocarbon. It is produced by many plants and animals ...

units, often with the molecular formula C₂₀H₃₂. They are biosynthesized by plants, animals and fungi via the

HMG-CoA reductase pathway The mevalonate pathway, also known as the isoprenoid pathway or HMG-CoA reductase pathway is an essential metabolic pathway present in eukaryotes, archaea, and some bacteria. The pathway produces two five-carbon building blocks called isopente ...

, with geranylgeranyl pyrophosphate being a primary intermediate. Diterpenes form the basis for biologically important compounds such as

retinol Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family found in food and used as a dietary supplement. As a supplement it is used to treat and prevent vitamin A deficiency, especially that which results in xeroph ...

retinal Retinal (also known as retinaldehyde) is a polyene chromophore. Retinal, bound to proteins called opsins, is the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision). Some microorganisms use reti ...

, and phytol. They are known to be

antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

and antiinflammatory.

Structures

As with most terpenes a huge number of potential structures exists, which may be broadly divided according to the number of rings present.

Biosynthesis

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 Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...

. 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

tocopherol Tocopherols (; TCP) are a class of organic chemical compounds (more precisely, various methylated phenols), many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rat ...

s and the phytyl functional group is used in the formation of chlorophyll ''a'', ubiquinones,

plastoquinone Plastoquinone (PQ) is an isoprenoid quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4-benzoquinone ...

and phylloquinone.

Diterpenoids

Diterpenes are formally defined as being

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

and thus contain no heteroatoms. Functionalized structures should instead be called diterpenoids, 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

and phytol.

Taxanes

Taxane Taxanes are a class of diterpenes. They were originally identified from plants of the genus '' Taxus'' (yews), and feature a taxadiene core. Paclitaxel (Taxol) and docetaxel (Taxotere) are widely used as chemotherapy agents. Cabazitaxel was FDA ...

s are class of diterpenoids featuring a taxadiene core. They are produced by plants of the genus ''

Taxus ''Taxus'' is a genus of coniferous trees or shrubs known as yews in the family Taxaceae. They are relatively slow-growing and can be very long-lived, and reach heights of , with trunk girth averaging . They have reddish bark, lanceolate, flat ...

'' (yew trees) and are widely used as

chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemother ...

agents.

Other

* ''Dodonaea petiolaris'' yields the diterpene ''ent''-3β-acetoxy-15,16-epoxylabda-8(17),13(16),14-trien-18-oic acid (C₂₂H₂₈O₆) or its enantiomer. * ''

Salvia divinorum ''Salvia divinorum'' (Latin: "sage of the diviners"; also called ska maría pastora, seer's sage, yerba de la pastora, magic mint or simply salvia) is a plant species with transient psychoactive properties when its leaves are consumed by che ...

'' yields Salvinorin A, a psychotropic drug

References