The involvement of the glucoalkaloid strictosidine in antimicrobial an
d antifeedant activity in Catharanthus roseus leaves was investigated.
Strictosidine and its deglucosylation product, specifically formed by
the enzyme strictosidine glucosidase, were shown to be active against
several microorganisms. In contrast, neither the intact glucoside, no
r the aglycone product(s) was found to exhibit antifeedant activity ag
ainst Spodoptera exigua larvae, as was found for intact C. roseus leav
es and leaf extracts. Besides alkaloids further downstream in the bios
ynthesis pathway, a more apolar, yet unidentified compound may be invo
lved in this activity.