Spirostanol Saponins from Asparagus sprengeri and Their Molluscicidal Activity

Abstract

Two new spirostane saponins namely (25R)-6α-[(β-D-glucopyranosyl)oxy]-5α-spirostan-3β-yl β-D-galactopyranoside (1) and (25R)-6α-[(β-D-glucopyranosyl)oxy]-27-hydroxy-5α-spirostan-3β-yl β-D-glucopyranoside (2), together with three known metabolites (25S)-5β-spirostan-3-β-yl O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranoside (3), (25R)-5α-spirostan-3-β-yl O-β-D-galactopyranosyl-(1→2)-O-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside (4) and (25R)-5α-spirostan-3-β-yl O-β-D-glucopyranosyl-(1→3)-O-[β-D-xylopyranosyl-(1→2)]-O-β-D-glucopyranosyl-(1→4)-β-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, ¹H, DEPT ¹³C NMR, ¹H-¹H 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.