Triterpene saponins from Cussonia arborea

Cussonia arborea A. Rich (Araliaceae) is a medium size tree that occurs in savannah of tropical and subtropical area of Africa. Cussonia species are generally used in folk medecines for treatment of dizziness and infertility in women, acne, diarrhea, syphilis, mental diseases, malaria and rhumatism [1]. The chemical and biological activities of this plant have not previously been investigated, but phytochemical studies on related species revealed the presence of terpenoid saponins and flavonoids [2,3]. In our continuing search for novel biologically active compounds from Cameroonian endemic plants, we investigated the stem bark of Cussonia arborea collected in the Western highlands of Cameroon. The combination of separation techniques (CC, VLC, MPLC) afforded seven triterpene saponins from the butanolic fraction of the methanol extract. Their structures were elucidated mainly by 1D- and 2D-NMR spectroscopic methods (¹H, ¹³C/DEPT, COSY, TOSCY, NOESY, HSQC, HMBC) and FABMS. Three of them were characterized as 3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl hederagenin 28-O-β-D-galactopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3-O-β-D-glucopyranosyl-(1→3)-β-D-xylopyranosyl-(1→2)-α-D-glucopyranosyl oleanolic acid 28-O-[α-L-arabinopyranosyl-(1→6)]-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl ester, 3-O-[α-L-rhamnopyranosyl-(1→4)]-[β-D-glucopyranosyl-(1→2)]-α-L-arabinopyranosyl oleanolic acid 28-O-β-D-galactopyranosyl-(1→6)-β-D-glucopyranosyl ester, new natural compounds.

References: 1. Adjanohoun, E. et al. (1991) Traditional Medicine and Pharmacopoeia, contribution to ethnobotanical and floristic studies in Western Nigeria; commission of Scientific and Technical Research/Organisation of African Unity. 2. Tapondjou, L. et al. (2003)J. Nat. Prod. 66: 1266–1269. 3. Mitaine-Offer, A.-C. et al. (2004) Biochem. Syst. Ecol. 32: 607–610