The chemical investigation of the fresh flowers of Albizia lebbeck (L.) Benth. (Fabaceae, Mimosoideae) led to the isolation of two new echinocystic acid saponins. They were isolated by using chromatographic methods and their structures were elucidated by detailed 1H and 13C NMR spectral data including 2 D-NMR (COSY, HSQC, HMBC and APT) spectroscopic techniques, high-resolution electrospray ionization mass spectrometry (HRESIMS) and acid hydrolysis. Their structures were established as 16-hydroxy-3-[[O-β-D-xylopyranosyl-(1→2)-O-α-L-arabinopyranosyl-(1→6)-2-(acetylamino)-2-deoxy-β-D-glucopyranosyl]oxy]-(3β,16α)-olean-12-en-28-oic acid O-6-deoxy-α-L-mannopyranosyl-(1→4)-O-6-deoxy-α-L-mannopyranosyl-(1→2)-β-D-glucopyranosyl ester (1) and 16-hydroxy-3-[[O-β-D-xylopyranosyl-(1→2)-O-α-L-arabinopyranosyl-(1→6)-2-(acetylamino)-2-deoxy-β-D-glucopyranosyl]oxy]-(3β,16α)-olean-12-en-28-oic acid 6-O-[(2S,3R,4R)-tetrahydro-3-hydroxy-4-(hydroxymethyl)-2-furanyl]-β-D-glucopyranosyl ester (2). Additionally, the permeability property and the capacity of interaction with biological membranes of compounds 1 and 2 were investigated.
Keywords: Albizia lebbeck; echinocystic acid saponins; structural elucidation; triterpenoid saponins.