Diterpene toxins

Sarcophyton species contain diterpenes up to 10% of their dry weight, and this large quantity of secondary metabolites plays an important role in the survival of Octo-corals with defensive, competitive, reproductive, and possibly pheromonal functions. Soft corals lacking physical defense thus seem to be protected from predation by the presence of diterpene toxins in their tissue. Nearly 25 species of this genus occurring in different seawaters have been examined chemically so far, and more than 80 cembranoid diterpenes have been isolated from the Sarcophyton genus since the 1970s. 

Mad honey. Common name for Rhododendron honey containing tetracyclic diterpene toxins ( grayanotox-ins) that can lead to atropine-like poisonings. 

Diterpenes from Euphorbiaceae are toxic to livestock, and so are daphnane and daphnetoxin, diterpenes from Daphne mezereum (Thymelaeaceae). Toxins fromRhododendron are diterpenes. 

Diterpene esters are primary dermal and gastrointestinal irritants. The amount of toxin found in the common greenhouse variety of poinsettia is minimal and very rarely causes symptoms. Irritation, whether dermal or oral, is rare. The poinsettia, despite its unfavorable reputation, appears for the most part to be innocuous. 

Four unusual chlorinated homo diterpenes, hamiltonins A-D (143 - 146), the sesterterpene hamiltonin E (147) and the toxins latrunculin A and B (148, 149) [123], were isolated from the brightly coloured dorid nudibranch Chromodoris hamiltoni (Family Chromodorididae) collected from the Aliwal shoal [124], Since latrunculin A and B were initially shown to cause concentration dependent changes in cell shape and actin organization [125], they have now become the most widely accepted tools for exploring the inhibition of actin polymerization in molecular biology [126],... 

C20H28O4, Mr 332.44, mp. 111-112 C, yellow needles, [a]o -188 (CHCI3), a diterpene with abietane structure from Callicarpa candicans, fish toxin. 

C22H24O8, Mr 416.43, needles, mp. 164-166 °C. Fu-ranocembranolide from seafans and flagellated corals of the genus Lophogorgia. L. is a diterpene with the 14-membered carbocylic ring of the cembranoids. L. is a potent neuromuscular toxin that causes an irreversible postsynaptic blockade of acetylcholine receptors. In this respect it resembles a- bungarotoxin, a cobra venom, LDso (mouse s.c.) 8 mg/kg. 

The terpenoid fraction of many conifers consists of 20-50% volatile monoterpenes and sesquiterpenes and 50-80% nonvolatile diterpene acids. In general, there is little variation in the diterpene fraction among trees of a particular species, although the monoterpene fraction often varies greatly. Alterations in the monoterpene content often determine whether attack by bark beetles will occur and be successful. The monoterpenes may be attractants, repellents, or toxins of not only the insects, but also the pathogenic fungi involved in these systems. The conversion of geranyl pyrophosphate to the parent compounds of the various cyclic types is catalyzed by monoterpene cyclases (see the subsection biosynthesis, above). 

Identification of new compounds may start with TLC analysis of plant extracts. For instance, Jakupovic et al. - isolated and further identified several diterpenes from Euphorbia segetalis. Similarly, chamomile essential oil (Chamomilla reticulata) was analyzed with 11 different development systems and the authors discussed both the most efficient (separation power) and the ideal way they are to be used to identify an unknown component in such a complex mixture, using the minimum number of TLC systems.This area of work still has to be investigated, considering the wide variety of the vegetal reign and of potential plant toxins. 

The role of sesquiterpenes and diterpenes in soldier secretions is little understood. Possibly sesquiterpenes, which are also common toxins in many poisonous plants, may sometimes act as feeding deterrents or inhibitors to vertebrate termite predators. Aristolochene, found in various Syntermes species, has a very high mammalian toxicity. The total secretion also has a powerful gamey smell, and an association between odour of a mound and palatability of the inhabitants could be easily formed. 

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