Cytotoxic Oleanane‐Type Saponins from the Leaves of Albizia anthelmintica Brongn.

Two new oleanane‐type saponins: β‐d‐xylopyranosyl‐(1 → 4)‐6‐deoxy‐α‐l‐mannopyranosyl‐(1 → 2)‐1‐O‐{(3β)‐28‐oxo‐3‐[(2‐O‐β‐d‐xylopyranosyl‐β‐d‐glucopyranosyl)oxy]olean‐12‐en‐28‐yl}‐β‐d‐glucopyranose (1) and 1‐O‐[(3β)‐28‐oxo‐3‐{[β‐d‐xylopyranosyl‐(1 → 2)‐α‐l‐arabinopyranosyl‐(1 → 6)‐2‐acetamido‐2‐deoxy‐β‐d‐glucopyranosyl]oxy}olean‐12‐en‐28‐yl]β‐d‐glucopyranose (2), along with two known saponins: (3β)‐3‐[(β‐d‐Glucopyranosyl‐(1 → 2)‐β‐d‐glucopyranosyl)oxy]olean‐12‐en‐28‐oic acid (3) and (3β)‐3‐{[α‐l‐arabinopyranosyl‐(1 → 6)‐[β‐d‐glucopyranosyl‐(1 → 2)]‐β‐d‐glucopyranosyl]oxy}olean‐12‐en‐28‐oic acid (4) were isolated from the acetone‐insoluble fraction obtained from the 80% aqueous MeOH extract of Albizia anthelmintica Brongn. leaves. Their structures were identified using different NMR experiments including: 1H‐ and 13C‐NMR, HSQC, HMBC and 1H,1H‐COSY, together with HR‐ESI‐MS/MS, as well as by acid hydrolysis. The four isolated saponins and the fractions of the extract exhibited cytotoxic activity against HepG‐2 and HCT‐116 cell lines. Compound 2 showed the most potent cytotoxic activity among the other tested compounds against the HepG2 cell line with an IC50 value of 3.60μm. Whereas, compound 1 showed the most potent cytotoxic effect with an IC50 value of 4.75μm on HCT‐116 cells.