Stress metabolites of Solanummelongena: biosynthetic studies and isolation of auberganol and α- and β-eudesmol

Abstract

Attempts to clarify the biosynthetic origin of the eggplant stress metabolite aubergenone (1) by incorporation of label from sodium [2-2H3,1-13C]acetate were frustrated by low yields and enrichment levels. However, the presence of deuterium in the biosynthetically significant 5-position was demonstrated by 2Hmr for the closely related auberganol (5) and α-and β-eudesmol (10 and 11), suggesting that these compounds, and hence also 1, are normal eudesmanes and not the products of a possible double rearrangement. Deuterium was also incorporated into the expected positions of 9-oxonerolidol (12), 9-oxynerolidol (13), and lubimin (4). Incorporation of label from [1,2-13C2]acetate could be determined satisfactorily only for 13 and its allylic isomer 14, corresponding with expectations. This is the first report of 5 as a natural product and of 10, 11, and the 10-epimer of 4 as eggplant stress metabolites.