Spirostanol Saponins from Asparagus sprengeri and their molluscicidal activity

Two new spirostane saponins namely (25R)-6 alpha-[(beta-D-glucopyranosyl)oxy]-5 alpha-spirostan-3 beta-yl beta-D-galactopyranoside (1) and (25R)-6 alpha-[(beta-D-glucopyranosyl)oxy]-27-hydroxy-5 alpha-spirostan-3 beta-yl beta-D-glucopyranoside (2), together with three known metabolites (25S)-5 beta-spirostan-3-beta-yl O-beta-D-glucopyranosyl-(1 -> 2)-beta-D-glucopyranoside (3), (25R)-5 alpha-spirostan-3-beta-yl O-beta-D-galactopyranosyl-(1 -> 2)-O-beta-D-glucopyranosyl-(1 -> 4)-beta-D-galactopyranoside (4) and (25R)-5 alpha-spirostan-3-beta-yl O-beta-D-glucopyranosyl-(1 -> 3)-O-[beta-D-xylopyranosyl-(1 -> 2)]-O-beta-D-glucopyranosyl-(1 -> 4)-beta-D-glactopyranoside (5) were identified from the leaves of Asparagus sprengeri Regel (Asparagaceae). Determination of the structures was based on chemical and spectroscopic data (HRESI-MS/MSn, H-1, DEPT C-13 NMR, H-1-H-1 COSY, HSQC and HMBC). The dry powder, the 1-butanol extract of the leaves, and the isolated compounds (3-5) exhibited molluscicidal properties against Biomphalaria alexandrina snails (the intermediate host of Schistosoma mansoni) [LC90 = 150, 40, 7, 10 and 13 ppm, respectively], while compounds 1 and 2 were molluscicidally inactive.