Oxygenated diterpenes

A series of complex oxygenated diterpenes is known to be antifeedant. Several of these occur in the Lamiaceae (Labiatae) and Verbenaceae, but are found in other families as well ( .g. in... 

Kupchan et al. [38] first isolated triptolide, a highly oxygenated diterpene from an ethanol ic extract of the Chinese medicinal plant Triptergium... 

The dramatic increase in terpene formation, accumulation, and emission in P. abies in response to methyl jasmonate is consistent with the effect of methyl jasmonate or jasmonic acid on many defense compounds in angiosperms. In conifers, jasmonates had been previously shown to promote the formation of heat shock and defense signaling proteins, to enhance resistance to pathogenic fimgi, and to promote colonization with ectomycorrhizae. In relation to terpenes, jasmonates had been shown to promote formation of an oxygenated sesquiterpene, todomatuic acid, and an oxygenated diterpene, paclitaxel (taxol), in cell cultures, but had never before been reported to enhance terpene accumulation in intact plants. 

Oleoresins characteristically contain 60% or more diterpenes by weight. Because of the resinous nature of this material and its tendency to polymerize in the presence of oxygen, diterpenes are major components of physical barriers to infection at wound sites (Croteau and Johnson, 1985). 

Diterpenes of this series are formed by rearrangement of the labdane skeleton during cyclization (Hanson, 1991 West, 1981) (Fig. 22.11). Many highly oxygenated diterpenes of this series are found in the Lamiaceae and Verbena-ceae. There are over 400 known clerodanes many of these are from Teucrium species (Lamiaceae) (Hanson, 1991). 

Several series of complex oxygenated diterpenes are known to have antifeedant properties. Many of these occur... 

Tursch B, Braekman JC, Daloze D, Dedeurwaerder H, Karlsson R (1978) Chemical studies of marine invertebrates. XXXI(l). Crassolide, a highly oxygenated diterpene from the soft coral lobophytum crassum. (Coeltmterata, Octocorallia, Alcyonacea). Bull Soc Chim Beiges 87 75... 

Marrero, J., Rodriguez, A.D., Baran, P., and Raptis, R.G. (2003) Isolation and structure of providenc in a highly oxygenated diterpene possessing a unique bicyclo[12.2.0]-hexadecane ring system from the sea plume Pseudopterogorgia hallos. Org. Lett., 5, 2551-2554. 

Yong, K.W.L., Salim, A.A., and Garson, M.J. (2008) New oxygenated diterpenes from an AustraHan nudibranch of the genus Chromodoris. Tetrahedron, 64, 6733-6738. 

Eight olibanum samples of unknown botanical origin have been analysed [26]. The chemical compositions are summarized in Table 10.3 for three of them. Both the olibanum coming from Somalia and that from a market in Ta izz (Yemen) have been attributed to Boswellia carteri or sacra on the basis of the occurrence of the characteristic diterpenes isoincensole and isoincensole acetate (128) together with diterpene 126. The absence of methylchavicol (38), oxygenated sesquiterpene 91 and diterpene 124 and the presence in relatively large amount of (3-caryophyllene (73), ot-humulene (78) and caryophyllene oxide (95) excluded the hypothesis of a B. serrata sample. 

Isodon diterpenes. Highly oxygenated.- -seco-ent-kaurane diterpenoids, the isodons (Figure 7), isolated from species of Isodon (now Rhabdosia)... 

Essential oils may comprise volatile compounds of terpenoid or non-terpe-noid origin. All of them are hydrocarbons and their oxygenated derivatives. Some may also contain nitrogen or sulphur derivatives. They may exist in the form of alcohols, acids, esters, epoxides, aldehydes, ketones, amines, sulphides, etc. Monoterpenes, sesquiterpenes and even diterpenes constitute the composition of many essential oils. In addition, phenylpropanoids, fatty acids and their esters, or their decomposition products are also encountered as volatiles [1-16, 21-33, 36-38]. 

C15H24) and diterpenes (C20H32), and oxygenated hydrocarbons such as alcohols, esters, aldehydes, ketones, ethers, and phenols. 

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