Figure 9.20 The guanosine derivative designated HF-7 from venom of Hololena curta, a funnel-web spider, and the amide of oxalic acid with agmatine (decarboxylated arginine) from a hunting spider Plectreurys tristis adapting derivatives of primary metabolites (compare section on spiders in Chapter 3, p. 52).

a-Tocopherol acetate (Figure 9.21) is present in the secretion of the pupae of the squash beetle Epilachna borealis. It is made from choris-mic acid via /?-hydroxybenzoic acid with isoprene units added. Tocopherol contains a completely reduced diterpene chain fused onto a trimethylhydroquinone. The extra methyl groups on the quinone part come from S-adenosylmethionine. Tocopherol is an antioxidant and is vitamin E in humans, so this application of the compound is curious. It is related to the ubiquinones, also known as coenzyme Q, they are primary metabolites, found in all cells, with a function in electron transport.

Figure 9.21 Outline of the formation of a-tocopherol acetate from p-hydroxybenzoic acid, a reduced terpene chain and additional methyl groups, and, for comparison, the formation of ubiquinones
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