New acylated triterpene saponins from Polygala arenaria

Eight new acylated triterpene saponins 1-8 were isolated from the roots of Polygala arenaria as four inseparable (E)/(Z) mixtures of the 4-methoxycinnamoyl and 3,4-dimethoxycinnamoyl derivatives by repeated MPLC over silica gel. Their structures were established mainly by 600-MHz 2D-NMR techniques (¹H,¹H-COSY, TOCSY, NOESY, HSQC, HMBC) as 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-galactopyranosyl-(1→4)-O-[β-D-glucopyranosyl-(1→3) ]-O-β-D-xylopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→2) {4-O-[(E)-4-methoxycinnamoyl]}-β-D-fucopyranosyl) ester and its (Z)-isomer (1/2), 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-galactopyranosyl-(1→4)-O-[β-D-glucopyranosyl-(1→3) ]-O-β-D-xylopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→2) -{4-O-[(E)-3,4-dimethoxycinnamoyl]}-β-D-fucopyranosyl) ester and its (Z)-isomer (3/4), 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-glucopyranosyl-(1→3)-O-α-L-arabinopyranosyl-(1→4) -O-α-L-rhamnopyranosyl-(1→2)-{4-O-[(E)-4-methoxycinnamoyl]} -β-D-fucopyranosyl) ester and its (Z)-isomer (5/6), and 3-O-(β-D-glucopyranosyl)presenegenin 28-(O-β-D-glucopyranosyl-(1→3)-O-α-L-arabinopyranosyl-(1→4) -O-α-L-rhamnopyranosyl-(1→2)-{4-O-[(E)-3,4-dimethoxycinnamoyl]} -β-D-fucopyranosyl) ester and its (Z)-isomer (7/8) (presenegenin= (2β,3β)-2,3,27-trihydroxyolean-12-ene-23,28-dioic acid). In our in vitro lymphocyte proliferation assay (Jurkat T-leukemia cells), a fraction containing 1-4 showed a concentration-dependent immunomodulatory effect. This effect was not found for the prosapogenin (tenuifolin=3-O-(β-D-glucopyranosyl)presenegenin), underlining the importance of the acyl-oligosaccharidic moiety.