Phytochemical study of the aerial parts of Zygophyllum geslini

Zygophyllum geslini Coss. (Zygophyllaceae), traditionally used as antidiabetic [1], was collected in the Algerian Central Sahara. From a methanolic extract of the aerial parts, a crude saponin mixture was obtained and submitted to successive solid/liquid preparative chromatographic methods, i.e. VLC, MPLC over silica gel and RP-18. Five saponins were isolated and purified, and their structures were established mainly by 600MHz 2D NMR techniques (COSY, TOCSY, NOESY, HSQC, HMBC) and mass spectrometry. Three new triterpene glycosides were identified as 3-O-α-L-rhamnopyranosyl-(1(→2)-α-L-arabinopyranosyl-(1(→2)-β-D-glucuronopyranosyl-urs-20(21)-en-28-oic acid-28-O-(2-O-sulfo-β-D-glucopyranosyl) ester, 3-O-(2-O-sulfo-β-D-glucuronopyranosyl)-urs-20(21)-en-28-oic acid-28-O-(2-O-sulfo-β-D-glucopyranosyl) ester, and 3-O-(2-O-sulfo-β-D-glucopyranosyl)-quinovic acid, together with the known zygophylosides E and G. Comparing the results obtained with different Zygophyllum species [2], the presence of the ursane-type aglycone and the sulfonyl moiety in these molecules may represent chemotaxonomic markers of this genus.

References: [1] Smati, D. et al. (2004) J. Ethnopharmacol. 95: 405–407. [2] Safir, O. et al. (1998) J. Nat. Prod. 61: 130–134.