Phytotoxic steroidal saponins from Agave offoyana leaves

A bioassay-guided fractionation of Agave offoyana leaves led to the isolation of five steroidal saponins (1-5) along with six known saponins (6-11). The compounds were identified as (25R)-spirost-5-en-2 alpha,3 beta-diol-12-one 3-O-{alpha-L-rhamnopyranosyl-(1 -> 3)-O-beta-D-glucopyranosyl-(1 -> 2)-O-[beta-D-xylopyranosyl-(1 -> 3)]-O-beta-D-glucopyranosyl-(1 ->-4)-O-beta-D-galactopyranoside) (1), (25R)-spirost-5-en-3 beta-ol-12-one 3-O-(alpha-L-rhamnopyranosyl-(1 -> 3)-O-beta-D-glucopyranosyl-(1 -> 2)-O-[beta-D-xylopyranosyl-(1 -> 3)]-O-beta-D-glu copyranosyl-(1 -> 4)-O-beta-D-galactopyranoside) (2), (25R)-spirost-5-en-3 beta-ol-12-one 3-O-{beta-D-xylopyrano syl-(1 -> 3)-O-beta-D-glucopyranosyl-(1 -> 2)-O-[beta-D-xylopyranosyl-(1 -> 3)]-O-beta-D-glucopyranosyl-(1 -> 4)-O-beta -D-galactopyranoside) (3), (25R)-26-O-beta-D-glucopyranosylfurost-5-en-3 beta,22 alpha,26-triol-12-one 3-O-{alpha-L-rhamnopyranosyl-(1 -> 3)-O-beta-D-glucopyranosyl-(1 -> 2)-O-[beta-D-xylopyranosyl-(1 -> 3)]-O-beta-D-glucopyrano syl-(1 -> 4)-O-beta-D-galactopyranoside} (4) and (25R)-26-O-beta-D-glucopyranosylfurost-5-en-3 beta,22 alpha,26-triol-12-one 3-O-{beta-D-xylopyranosyl-(1 -> 3)-O-beta-D-glucopyranosyl-(1 -> 2)-O-[beta-D-xylopyranosyl-(1 -> 3)]-O-beta-D-glucopyranosyl-(1 -> 4)-O-beta-D-galactopyranoside) (5) by comprehensive spectroscopic analysis, including one- and two-dimensional NMR techniques, mass spectrometry and chemical methods. The phytotoxicity of the isolated compounds on the standard target species Lactuca sativa was evaluated. (C) 2014 Elsevier Ltd. All rights reserved.