Bioactive Saponins from Astragalus suberi L. Growing in Yemen

Abstract

From the aerial parts of Astragalus suberi L., Fabaceae, seven saponins were isolated. Based on spectral data (IR, 1H and 13C NMR and HR-FABMS), the structures were established as 3-O-(β-ᴅ-glucopyranosyl)-soyasapogenol B (1); 3-O-(β-ᴅ-glucuronopyranosyl)- soyasapogenol B (2); 3-O-[β-ᴅ-galactopyranosyl (1→2)-β-ᴅ-glucopyranosyl]-soyasapogenol B (3); 3-O-[α-ʟ-rhamnopyranosyl (1→2)-β-ᴅ-galactopyranosyl (1→2)-β-ᴅ-glucopyranosyl]- soyasapogenol B (4); 3-O-[α-ʟ-rhamnopyranosyl (1→2)-β-ᴅ-galactopyranosyl (1→2)-β-ᴅ-glucopyranosyl]-11-hydroxy-soyasapogenol B (5); 3-O-[α-ʟ-rhamnopyranosyl (1→2)-β-ᴅ-galactopyranosyl (152)-β-ᴅ-glucuronopyranosyl]-soyasapogenol B (6) and 3-O-[α-ʟ-rhamnopyranosyl (1→2)-β-ᴅ-galactopyranosyl (1→2)-β-ᴅ-glucuronopyranosyl]-complogenin (7). The isolated saponins exhibited antibacterial activities against Gram-positive and Gramnegative bacteria with minimum inhibitory concentration values > 100 μg/ml, antifungal activity against all the strains tested with minimum fungicidal concentration values between 25 and 50 μg/ml and inhibited the growth of Hep-2 (human carcinoma of larynx), with IC50 values between 50 μg/ml (compounds 5-7) and 100 μg/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 μg/ml (compounds 1-4 and 6)]