From the roots of three species of Acanthophyllum (Caryophyllaceae), two new gypsogenic acid glycosides, 1 and 2, were isolated, 1 from A. sordidum and A. lilacinum, 2 from A. elatius and A. lilacinum, together with three known saponins, glandulosides B and C, and SAPO50. The structures of 1 and 2 were established mainly by 2D NMR techniques as 23-O-beta-D-galactopyranosylgypsogenic acid-28-O-beta-D-glucopyranosyl-(1-->3)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-galactopyranoside (1) and gypsogenic acid-28-O-beta-D-glucopyranosyl-(1-->3)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-galactopyranoside (2). The cytotoxicity of several of these saponins was evaluated against two human colon cancer cell lines (HT-29 and HCT 116).
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 3Introduction. ester, which represents a chemotaxonomic marker [2] (presenegenin ¼ (2b,3b,4a)-2,3,27-trihydroxyolean-12-ene-23,28-dioic acid). This prompted us to study the genus Securidaca in the framework of our study of the saponin constituents of the Polygalaceae family. In a previous contribution, we reported on the isolation and characterization of trimethoxycinnamoyl saponins from S. longepedunculata [3]. We have now extended our investigations to another species S. welwitschii Oliv. It is a liana (until 25 m high) widely distributed in Guinea, Cameroon, Democratic Republic of Congo, Angola, and Uganda [4]. This plant was reported to contain methyl salicylate and one major saponin deriving from presenegenin. Its sugar part was constitued by glucose, galactose, xylose, arabinose, fucose, and rhamnose [4]. Its use in traditional medicine is rare excepted for eyes affections [4]. In this article, we describe the isolation from the stem barks and the structural elucidation of five new triterpene saponins with presenegenin as aglycon, and one known sucrose diester previously isolated from S. longepedunculata [5].
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