Variation in chemical composition, antibacterial and antioxidant activity of fresh and dried Acacia leaf extracts

This study investigated differences in chemical composition and biological activity of fresh and dried leaf extracts of Acacia galpinii, A. karroo, A. xanthophloea and A. sieberiana occurring in southern Africa. Leaf material was extracted first with acetone and subsequently with chloroform. Drying of leaves led to an increase in the dry mass extracted by acetone and a decrease in the dry mass extracted by the more nonpolar chloroform as well as an overall decrease in the dry mass extracted. The chemical profile, determined by TLC, of fresh and dry material of the same species differed. The antibacterial activity was higher in extracts from dried than fresh leaves with the exception of A. xanthophloea, which was overall, the most active with an MIC of 78mug ml(-1) against Staphylococcus aureus and 160mug ml(-1) against Escherichia coli. There were at least three free radical scavenging compounds present in acetone leaf extracts of all species. This is the first report of antibacterial and free radical scavenging activity for these species.