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.
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.
Cyclopiazonic acid (α-CPA), a mycotoxin and a fungal neurotoxin, is made by the molds Aspergillus and Penicillium. It is an indole-tetramic acid that serves as a toxin due to its ability to inhibit calcium-dependent ATPases found in the endoplasmic and sarcoplasmic reticulum. This inhibition disrupts the muscle contraction-relaxation cycle and the calcium gradient that is maintained for proper cellular activity in cells.
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.
Squalene synthase (SQS) or farnesyl-diphosphate:farnesyl-diphosphate farnesyl transferase is an enzyme localized to the membrane of the endoplasmic reticulum. SQS participates in the isoprenoid biosynthetic pathway, catalyzing a two-step reaction in which two identical molecules of farnesyl pyrophosphate (FPP) are converted into squalene, with the consumption of NADPH. Catalysis by SQS is the first committed step in sterol synthesis, since the squalene produced is converted exclusively into various sterols, such as cholesterol, via a complex, multi-step pathway. SQS belongs to squalene/phytoene synthase family of proteins.
Penitrem A (tremortin) is an indole-diterpenoid mycotoxin produced by certain species of Aspergillus, Claviceps, and Penicillium, which can be found growing on various plant species such as ryegrass. Penitrem A is one of many secondary metabolites following the synthesis of paxilline in Penicillium crostosum. Penitrem A poisoning in humans and animals usually occurs through the consumption of contaminated foods by mycotoxin-producing species, which is then distributed through the body by the bloodstream. It bypasses the blood-brain barrier to exert its toxicological effects on the central nervous system. In humans, penitrem A poisoning has been associated with severe tremors, hyperthermia, nausea/vomiting, diplopia, and bloody diarrhea. In animals, symptoms of penitrem A poisoning has been associated with symptoms ranging from tremors, seizures, and hyperthermia to ataxia and nystagmus.
Momilactone B is an allelopathic agent produced from the roots of rice. It has been shown to be produced in high concentrations by the roots of rice seedlings. The production of momilactone B has also been induced in response to infection by blast fungus or irradiated with UV light. More recently it has been shown to be a potential chemotherapeutic agent against human colon cancer.
Indole is an organic compound with the formula C6H4CCNH3. Indole is classified as an aromatic heterocycle. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered pyrrole ring. Indoles are derivatives of indole where one or more of the hydrogen atoms have been replaced by substituent groups. Indoles are widely distributed in nature, most notably as amino acid tryptophan and neurotransmitter serotonin.
Lyngbyatoxin-a is a cyanotoxin produced by certain cyanobacteria species, most notably Moorea producens. It is produced as defense mechanism to ward off any would-be predators of the bacterium, being a potent blister agent as well as carcinogen. Low concentrations cause a common skin condition known as seaweed dermatitis.
ent-Sandaracopimaradiene synthase is an enzyme with systematic name ent-copalyl-diphosphate diphosphate-lyase [ent-sandaracopimara-8(14),15-diene-forming]. This enzyme catalyses the following chemical reaction
Terpentetriene synthase is an enzyme with systematic name terpentedienyl-diphosphate diphosphate-lyase (terpentetriene-forming). This enzyme catalyses the following chemical reaction
Aphidicolan-16β-ol synthase (EC 4.2.3.42, PbACS) is an enzyme with systematic name 9α-copalyl-diphosphate diphosphate-lyase (aphidicolan-16β-ol-forming). This enzyme catalyses the following chemical reaction
Phyllocladan-16α-ol synthase (EC 4.2.3.45, PaDC1) is an enzyme with systematic name (+)-copalyl-diphosphate diphosphate-lyase (phyllocladan-16α-ol-forming). This enzyme catalyses the following chemical reaction
Terpentedienyl-diphosphate synthase is an enzyme with systematic name terpentedienyl-diphosphate lyase (decyclizing). This enzyme catalyses the following chemical reaction
Fumitremorgins are tremorogenic metabolites of Aspergillus and Penicillium, that belong to a class of naturally occurring 2,5-diketopiperazines.
Akuammicine is a monoterpene indole alkaloid of the Vinca sub-group. It is found in the Apocynaceae family of plants including Picralima nitida, Vinca minor and the Aspidosperma.
Penicillium paxilli is an anamorph, saprophytic species of the genus Penicillium which produces paxilline, paxisterol, penicillone, pyrenocine A, paspaline B and verruculogene. Penicillium paxilli is used as a model to study the biochemistry of the indol-diterepene biosynthesis
Lolitrem B is one of many toxins produced by a fungus called Epichloë festucae var. lolii), which grows in Lolium perenne. The fungus is symbiotic with the ryegrass; it doesn't harm the plant, and the toxins it produces kill insects that feed on ryegrass. Lolitrem B is one of these toxins, but it is also harmful to mammals. The shoots and flowers of infected ryegrass have especially high concentrations of lolitrem B, and when livestock eat too much of them, they get perennial ryegrass staggers. At low doses the animals have tremors, and at higher doses they stagger, and at higher yet doses the animals become paralyzed and die. The blood pressure of the animals also goes up. The effect of the lolitrem B comes on slowly and fades out slowly, as it is stored in fat after the ryegrass is eaten. The condition is especially common in New Zealand and Australia, and plant breeders there have been trying to develop strains of fungus that produce toxins only harmful to pests, and not to mammals.
Conophylline is a autophagy inducing vinca alkaloid found in several species of Tabernaemontana including Ervatamia microphylla and Tabernaemontana divaricata. Among its many functional groups is an epoxide: the compound where that ring is replaced with a double bond is called conophyllidine and this co-occurs in the same plants.
Cytochrome P450, family 76, also known as CYP76, is a cytochrome P450 family in land plants, related to the biosynthesis of many plant monoterpenes and diterpenes such as 8-hydroxygeraniol, tanshinone and alkannin. The first gene identified in this family is the CYP76A1 and CYP76A2 from the eggplant.
