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 ( 1 H, 1 H‐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=(2 β ,3 β )‐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 acyloligosaccharidic moiety.