Occurrence of the insecticidal 16,17-didehydro-16(E)-stemofoline in Stemona collinsae

The occurrence of two alkaloids, 16,17-didehydro-16(E)-stemofoline and its isomer at C-4, 16,17-didehydro-4(E)-16(E)-stemofoline, were found together with a known insecticidal compound, stemofoline, in Stemona collinsae. The 16,17-didehydro- 16(E)stemofoline displayed higher insecticidal and antifeedant activities against the diamondback moth larvae than stemofoline. (C) 2001 Elsevier Science Ltd. All rights reserved.