Phenotype-specific apoptosis induced by three new triterpenoid saponins from Albizia glaberrima (Schumach. & Thonn.) Benth.

As part of our search of new bioactive saponins from Cameroonian medicinal plants, phytochemical investigation of the roots of Albizia glaberrima led to the isolation of three new oleanane-type saponins, named glaberrimosides A-C (1-3). Their structures were established by direct interpretation of their spectral data, mainly HRESIMS, 1D NMR (1H, 13C NMR, and DEPT) and 2D NMR (COSY, ROESY, HSQC and HMBC) as 3-O-[α-L-arabinopyranosyl-(1 → 6)-[β-D-glucopyranosyl-(1 → 2)]-β-D-glucopyranosyl]-28-O-[β-D-glucopyranosyl-(1 → 6)-[β-d-glucopyranosyl-(1 → 2)]-β-D-glucopyranosyl]-oleanolic acid (1), 3-O-[α-L-arabinopyranosyl-(1 → 6)-[β-D-glucopyranosyl-(1 → 2)]-β-D-glucopyranosyl]-28-O-[β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl]-oleanolic acid (2), and 3-O-[β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl]-28-O-[β-D-glucopyranosyl-(1 → 6)-[β-D-fucopyranosyl-(1 → 2)]-β-D-glucopyranosyl]-oleanolic acid (3). The pro-apoptotic effect of the three saponins was evaluated on three human cell lines (pancreatic carcinoma AsPC-1, hematopoietic monocytic THP-1, and human fibroblast cell line BJ). Saponins 1-3 specifically induced apoptosis of pancreatic carcinoma cell (AsPC-1) in a dose-dependent manner. More interestingly, there were inactive on monocytic (THP-1) and normal human fibroblast (BJ) cell lines.