The diversity of Stemona stilbenoids as a result of storage and fungal infection.

In relation to their biogenetic origin, 68 Stemona stilbenoids have been grouped into four structural types and are listed in order of increasing substitution pattern. Besides different hydroxylations and methoxylations, the rare C-methylations of the aromatic rings represent a typical chemical feature of these compounds. The formation of phenylbenzofurans constitutes another important chemical character separating Stemona species into two groups consistent with morphological and DNA data. Fungal infection leads to an increasing accumulation of stilbenes, dihydrostilbenes, and phenylbenzofurans with unsubstituted A-rings, suggesting the ecological role of these compounds as phytoalexins. Further oxygenations and methylations of both rings are interpreted as a result of aging or the drying processes. Bioautographic tests on TLC plates and germ-tube inhibition assays in microwells against four different fungi exhibited antifungal activities for almost all stilbenoids tested. Some derivatives also showed effects against yeasts and bacteria. Further activities may also be seen as dormancy-inducing factors of Stemona species occurring in periodically dry habitats. A leucotriene biosynthesis inhibition assay using 15 stilbenoids showed interesting structure-activity relationships, with more potent effects of some compounds than the commercial 5-lipoxygenase inhibitor zileuton being observed. Potential neuroprotective activities have been reported for three dihydrostilbene glucosides against 6-hydroxydopamine-induced neurotoxicity in human neuroblastoma SH-SY5Y cells.