An aphid repellent glycoside from Solanum laxum.

A spirostanic saponin was isolated from the ethanolic extract of the aerial parts of Solanum laxum Steud. The compound, named luciamin, was characterised by NMR spectroscopy, mass spectrometry and chemical methods, as (22R, 25S)-spirost-5-en-3 beta, 15 alpha-diol 3-O-|beta-D-glucopyranosyl (1 --> 2)-beta-D-glucopyranosyl-( 1 --> 4)-[alpha-L-rhamnopyranosyl-( 1 --> 2)]-beta-D-galactopyranoside|. The compound was tested against the aphid Schizaphis graminum by incorporation in artificial diets. It showed a deterrent (toxic) activity against the insect and is the first spirostane glycoside reported to have this activity.