Presenegenin Glycosides from Securidaca welwitschii

摘要

The five new presenegenin glycosides 1–5 were isolated from Securidaca welwitschii, together with one known sucrose diester. Compounds 1–4 were obtained as pairs of inseparable (E)/(Z)-isomers of a 3,4-dimethoxycinnamoyl derivative, i.e., 1/2 and 3/4. Their structures were elucidated mainly by 2D-NMR techniques and mass spectrometry as 3-O-(β-D-glucopyranosyl)presenegenin 28-{O-β-D-xylopyranosyl-(1→4)-O--L-rhamnopyranosyl-(1→2)-O-[β-D-glucopyranosyl-(1→3)]-4-O-[(E)-3,4-dimethoxycinnamoyl]-β-D-fucopyranosyl} ester (1) and its (Z)-isomer 2, 3-O-(β-D-glucopyranosyl)presenegenin 28-{O-β-D-galactopyranosyl-(1→4)-O-β-D-xylopyranosyl-(1→4)-O-3-O-acetyl--L-rhamnopyranosyl-(1→2)-O-[β-D-glucopyranosyl-(1→3)]-4-O-[(E)-3,4-dimethoxycinnamoyl]-β-D-fucopyranosyl} ester (3) and its (Z)-isomer 4, and 3-O-(β-D-glucopyranosyl)presenegenin 28-[O-β-D-galactopyranosyl-(1→3)-O-β-D-xylopyranosyl-(1→4)-O--L-rhamnopyranosyl-(1→2)-β-D-fucopyranosyl] ester (5) (presenegenin=(2β,3β,4)-2,3,27-trihydroxyolean-12-ene-23,28-dioic acid).