Planta Med 2014; 80 - P1L75
DOI: 10.1055/s-0034-1394732

Three new triterpenoid saponins from Albizia glaberrima roots

L Simo 2, SA Azouaou 1, M Tsoukalas 1, DE Pegnyemb 2, CD Muller 1, A Lobstein 1
  • 1University of Strasbourg, Faculty of Pharmacy, Laboratory of Pharmacognosy and Bioactive Natural Products (UMR 7200), 74, route du Rhin, CS60024, 67400 Illkirch Graffenstaden, France
  • 2University of Yaoundé, Faculty of Sciences, Department of Organic Chemistry, Laboratory of Pharmaco-chemistry of natural substances, BP 812, Yaoundé, Cameroun

Albizia glaberrima (Schumach. & Thonn.) Benth (Mimosaceae) is a large emergent tree up to 30 m high widely distributed in the Northeast, West, West-Central, East and South tropical Africa [1]. As part of our research of new bioactive saponins from Cameroonian medicinal plants, chemical investigation of the roots of A. glaberrima has led us to the isolation and structure elucidation of three new oleanane-type saponins named glaberrimosides A-C:

  • 3-O-[α-L-arabinopyranosyl-(1→6)-[α-L-arabinopyranosyl-(1→2)]-β-D-glucopyranosyl]-28-O-[β-D-glucopyranosyl-(1→6)-[β-D-glucopyranosyl-(1→2)]-β-D-glucopyranosyl] oleanolic acid

  • 3-O-[α-L-arabinopyranosyl-(1→6)-[α-L-arabinopyranosyl-(1→2)]-β-D-glucopyranosyl]-28-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl] oleanolic acid

  • 3-O-[α-L-arabinopyranosyl-(1→6)-[β-D-xylopyranosyl-(1→2)]-β-D-glucopyranosyl]-28-O-[β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl] oleanolic acid.

These structures were established by direct interpretation of their spectral data, mainly 1D NMR (1H, 13C NMR, and DEPT) and 2D NMR (COSY, NOESY, HSQC and HMBC) experiments, and HRESIMS. We then investigated the pro-apoptotic activity of these purified saponins on human pancreatic adenocarcinoma (AsPC-1) cells, using capillary cytometry. Compounds 1 – 3 induced cellular apoptosis with IC50 of 35µM, 433µM and 60µM, respectively. So, A, glaberrima contain cytotoxic oleanane-type triterpene saponins but not cytotoxic acacic-type saponins, identified in other Albizia species [2].

Keywords: Oleanane saponins, cytotoxicity

References:

[1] Arbonier. M. (2002). Arbres, arbustes et lianes des zones d'Afrique de l'Ouest.

[2] MA Lacaille Dubois et al. (2011) Phytochem. Rev. 10, 565 – 584.