In vitro: |
Archives of Biochemistry and Biophysics, 01 Apr 1978, 187(2):307-314. | Biosynthesis of aromatic monoterpenes: conversion of gamma-terpinene to p-cymene and thymol in Thymus vulgaris L.[Reference: WebLink] | METHODS AND RESULTS: The major components of the volatile oil of thyme (Thymus vulgaris L.) are the aromatic monoterpenes, thymol (38%) and p-cymene (23%), and the cyclic diene, γ-terpinene (28%). The time course of incorporation of 14CO2 into the volatile terpenoids of thyme cuttings suggested a biosynthetic sequence by which γ-terpinene gave rise to p-cymene, which in turn yielded thymol. Intact leaves from young thyme plants converted exogenous γ-[G-3H] terpinene into p-cymene and thymol, whereas p-[G-3H]cymene gave rise to only thymol in this tissue. Preincubation of the tissue with unlabeled p-cymene followed by incubation with γ-[G-3H]terpinene resulted in an increase of radioactivity inp-cymene and a substantial decrease of radioactivity in thymol. Similar isotopic dilution experiments with other possible intermediates, such as α-terpinene and terpinen-4-ol, produced no significant change in product distribution. All of the biosynthetic products were identified by radio gas-liquid chromatography and by the synthesis of several derivatives, which were analyzed by radio chromatography or crystallized to constant specific activity.
CONCLUSIONS:
These results provide, for the first time, strong evidence that thymol is biosynthesized by the aromatization of γ-terpinene to p-cymene followed by hydroxylation of p-cymene. |
|