Bioactive saponins from Astragalus suberi L. growing in Yemen

From the aerial parts of Astragalus suberi L., Fabaceae, seven saponins were isolated. Based on spectral data (IR, H-1 and C-13 NMR and HR-FABMS), the structures were established as 3-O-(beta-D-glucopyranosyl)-soyasapogenosol B (1); 3-O-(beta-D-glucuronopyranosyl)-soyasapogenol B (2); 3-O-{[}beta-D-galactopyranosyl (1 -> 2)-beta-D-glucopyranosyl]-soyasapogenol B (3); 3-O-{[}alpha-L-rhamnopyranosyl (1 -> 2)-beta-D-galactopyranosyl (1 -> 2)-beta-D-glucopyranosyl]-soyasapogenol B (4); 3-O-{[}alpha-L-rhamnopyranosyl (1 -> 2)-beta-D-galactopyranosyl (1 -> 2)-beta-D-ghlcopyranosyl]-11-hydroxy-soyasapogenol B (5); 3-O-{[}alpha-L-rhamnopyranosyl (1 -> 2)-beta-D-galactopyranosyl (1 -> 2)-beta-D-glucuronopyranosyl]-soyasapogenol B (6) and 3-O-{[}alpha-L-rhamnopyranosyl (1 -> 2)-beta-D-galactopyranosyl (1 -> 2)-beta-D-glucuronopyranosyl]-complogenin (7). The isolated saponins exhibited antibacterial activities against Gram-positive and Gram-negative bacteria with minimum inhibitory concentration values > 100 mu g/ml, antifungal activity against all the strains tested with minimum fungicidal concentration values between 25 and 50 mu gml and inhibited the growth of Hep-2 (human carcinoma of larynx), with IC50 values between 50 mu g/ml (compounds 5-7) and 100 mu g/ml (compounds 1-4), and Hela (human carcinoma of cervix) cell lines in culture with different IC50 values {[}74 (compound 7), 98 (compound 5) and 180 mu g/ml (compounds 1-4 and 6)].