Involvement of strictosidine as a defensive chemical in Catharanthus roseus

The involvement of the glucoalkaloid strictosidine in antimicrobial and antifeedant activity in Catharantus 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, nor the aglycone product(s) was found to exhibit antifeedant activity against Spodoptera exigua larvae, as was found for intact C. roseus leaves and leaf extracts. Besides alkaloids further downstream in the biosynthesis pathway, a more apolar, yet unidentified compound may be involved in this activity.