New Acylated Triterpene Saponins from Polygala arenaria

Abstract

AbstractEight 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.