Antibacterial and Antioxidant Activities of Two New Kaempferol Glycosides Isolated from Solenostemma argel Stem Extract

Chemical constituents, antibacterial and antioxidant activities of the 70% aqueous ethanolic extract of Solenostemma argel stems (AE) were investigated. Its chromatographic, chemical and spectral analysis revealed the presence of two new natural kaempferol glycosides namely: kaempferol 3-O-α-D-glucopyranosyl (1→2) β-D-xylopyranoside and kaempferol 3-O-α-L-arabinopyranosyl (1→2) β-D-galactopyranoside, together with the following known compounds:- kaempferol 3-O-α-L-arabinoside; 3-O-β-D-xyloside; 7-O-α-L-rhamnoside; 7-O- α-L-arabinoside; 3,7-di-O- β-D-glucoside; 3,7-di-O- α-L-rhamnoside and kaempferol. The two new natural kaempferol glycosides and its extract (AE) were active against both Gram-positive and Gram-negative bacteria to some extent. The results presented here for the antioxidant activity, using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free-radical assay, indicated a high radical scavenging activity of (AE) and a moderate activity for the isolated new compounds, so consequently we can say that they might be a valuable natural antioxidant source.