Presenegenin glycosides from securidaca welwitschii

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-α-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-α-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-α-L-rhamnopyranosyl- (1→2)-β-D-fucopyranosyl] ester (5) (presenegenin=(2β,3β, 4α)-2,3,27-trihydroxyolean-12-ene-23,28-dioic acid).