Molluscicidal steroidal saponins and lipid content of Agave decipiens

GLC analysis of the petrol extract of the leaves of Agave decipiens revealed that n-hexacosane was the main hydrocarbon, beta-sitosterol the main sterol and oleic acid the main fatty acid. Two spirostanol and two furostanol saponins have been isolated from the methanolic extract. The structures of these saponins were established as 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 4)]-beta-D-glucopyranosyl-26-O-beta-D-glucopyranosyl-22 alpha-methoxy-(25R)-furost-5-ene-3 beta,26-diol (1), neoruscogenin 1-O-beta-D-glucopyranosyl-(1 --> 3)-[alpha-L-rhamnopyranosyl-(1 --> 2)]-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranoside (2), 1-O-alpha-L-rhamnopyranosyl-(1 --> 2)-[alpha-L-rhamnopyranosyl-(1 --> 4)]-beta-D-glucopyranosyl-26-O-beta-D-glucopyranosyl-22-O-methylfurasto-5,25(27)-diene-1 beta,3 beta,22,26-tetraol (3) and neohecogenin 3-O-beta-D-glucopyranosyl-(1 --> 3)-[beta-D-xylopyranosyl-(1 --> 3)-beta-D-xylopyranosyl-(1 --> 2)]-beta-D-glucopyranosyl-(1 -, 4)-P-D-galactopyranoside (4). Saponins 2 and 4 showed high molluscicidal activity against B. alexandrina snails (LC90 = 13 and 6 ppm, respectively), whereas saponins 1 and 3 were inactive up to 50 ppm. (C) 1999 Elsevier Science B.V. All rights reserved.