Terpene biosynthesis. Part V. Interconversions of some monoterpenes in higher plants and their possible role as precursors of carotenoids
Feeding of [14C]-labelled p-menth-1-en-8-ol (α-terpineol) or trans-thujan-3-one (isothujone) to Tanacetum vulgare L. or 3,7-dimethylocta-2,6-dien-1-ol (geraniol) to Artemisia annua L. led to significant (0.14–6.7%) uptake of tracer into carotenoids, and the labelling pattern suggested incorporation of either undegraded C10 units or the biogenetic equivalent of 3,3-dimethylallyl pyrophosphate. Tracer uptake (ca. 0.2%) into chlorophyll was consistent with degradation of the precursors to C2 units.
[14C]p-Menth-1-en-8-ol was converted directly into isothujone in T. vulgare, but experiments with [14C,3H]isothujone showed that although possible direct conversion into thujols occurred within 40 h of feeding, longer metabolism times led to extensive degradation of the additive and scrambling of its tracer into other monoterpenes.