Biosynthesis of γ-bisabolene in tissue cultures of Andrographispaniculata

Abstract

Experiments with intact callus cultures of a. paniculata and a derived cell-free system established that; the biosynthesized .gamma.-bisabolene has the Z-configuration the biosynthetic intermediate is a 6-trans-13 and not a 6-cis-15 farnesyl pyrophosphate; in paniculide B 17, and probably also in .gamma.-bisabolene 14, the ring carbon derived from C-2 of mevalonate is anti to the side chain; mevalonolactone and trans -trans-farnesylpyrophosphate are incorporated into .gamma.-bisabolene without hydrogen loss respectively from C-5 and C-1; cyclization to the bisabolenyl cation therefore does not involve prior trans to cis isomerization of the terminal double bond of farnesol by a redox mechanism; taken together with previous findings, Andrographis cultures apparently contain 2 independently functioning enzymes; a trans-trans- to cis-trans-farnesol isomerase and a trans-trans-farnesylpyrophosphate isomerase-cyclase. The absolute configuration of paniculide B has been established by an X-ray crystallographic analysis of its bis-p-bromobenzoate.