Some aspects of monoterpene biosynthesis

Biosynthesis of terpenes present some special features. Incorporations of precursors are generally low. Degradation of substrates or higher terpenes into smaller units and their reutilisation into lower terpenes cause randomisation of the labels. Unbalanced distribution of the labels from labelled mevalonalactone (mva) into isopentenyl pyrophosphate and dimethylallyl pyrophosphate moieties and incorporation of amino acids into terpenes are some of the other special features of monoterpene biosynthesis. Bakuchiol, a meroterpene isolated from the plantPsoralea corylifolia provides a good model for biosynthetic studies pertaining to some of the above points. Using substrates labelled with suitable isotopes, it has been established that bakuchiol is biosynthesised from one phenylpropane and twomva units. Incorporation of leucine into bakuchiol has also been observed. Degradation of biosynthesised bakuchiol indicated extensive randomisation of the labels, thus its terpenic part is biosynthesised by the normal mevalonate pathway.