MODEL SYSTEMS FOR THE BIOLOGICAL OXIDATION OF MONOTERPENE HYDROCARBONS

Abstract

Photooxygenations of α–thujene and sabinene in the presence of chloroplast preparations from Tanacetum vulgäre or Juniperus sabina and of various dyes have been studied as possible model systems for the biosynthesis of oxygenated monoterpenes. Evidence is presented for the formation of a chlorophyll–oxygen complex and for the involvement of both singlet (excited state) and triplet (ground state) oxygen in some reactions. In addition, peroxidases capable of cleaving a range of monoterpene hydroperoxides were detected in the leaves of both plant species.

It is concluded that chloroplasts in vivo probably promote oxidation of sabinene by radical–type processes involving ground state oxygen, and the initially formed products can be converted into either thujyl or sabinyl derivatives in different plant species. α–Thujene is probably not a precursor for these monoterpenes in vivo.