Biosynthesis of Cucurbitacins in Bryonia dioica Seedlings

Abstract

The biosynthesis of cucurbitacins during the seed germination of Bryonia dioica was studied by analysis of the cucurbitacin-triterpenoid fraction and by tracer experiments with acetate-[2-¹⁴C]. Isolation of 10α-cucurbita-5,24-dien-3β-ol (9a), the simplest tetracyclic triterpene with a cucurbitane skeleton, supports the view that (9a) is the general precursor of cucurbitacins. Moreover, following the tracer experiments, cucurbitacin E (1a) was the first cucurbitacin formed, whereas the less oxygenated bryodulcosigenin (4a) was not detectable during germination of the plant.

In the course of the present investigation, a new pentacyclic triterpene, isomultiflorenol (11a) (possible precursor of bryonolic acid (5a)), was also isolated.

Key Word Index

Bryonia dioica - Cucurbitaceae - Cucurbitacins - Triterpenes - Biosynthesis