In vitro biological effects of two anti-diabetic medicinal plants used in Benin as folk medicine

Background: Extracts from Polygonum senegalensis (Polygonaceae) and Pseudocedrela kotschyi (Meliaceae) are two important traditionally used medicinal plants in rural Benin to treat many diseases and notably type 2 diabetes. The aim of the study was to investigate the a-glucosidase inhibition, antioxidant and antibacterial activities of those plants extract: Polygonum senegalensis leaves, and Pseudocedrela kotschyi root. Methods: Hydro-alcoholic (50%) extracts were analyzed for their phytochemical content and tested for their inhibition potency on a-glucosidase from Saccharomyces cerevisiae. Antioxidant activities were assessed using the DPPH, ORAC, FRAP and DCFH-DA (cell based) assay. Finally, the antibacterial activity was evaluated using MIC determination on four Gram-positive cocci (Bacillus subtilis, Clostridium difficile, Enterococcus faecalis, Staphylococcus aureus), three Gram-negative bacilli (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae), and the yeast Candida albicans. Results: Each extract presented significant a-glucosidase inhibition and antioxidant activities. Polygonum senegalensis leaf extracts were the most active in each in vitro assay with an IC50 = 1.5 mu g/ml for a-glucosidase inhibition and an IC50 = 6.8 mu g/ml for DPPH scavenging, -4.5 mu mol Fe II/g of dry matter -9366 mu mol Trolox / g DW - for FRAP and ORAC values, respectively. IC50 = 2.3 mu g GA / ml for DCFH-DA assay. Concerning its antibacterial activity, a growth inhibitory effect was observed only against three Gram negative bacilli: B. subtilis, E. faecalis, S. aureus and the yeast C. albicans at high concentration. Conclusion: The results showed that the semi alcoholic extract of the two studied plants possess a-glucosidase inhibitory activity, antioxidant potency, and low antibacterial effect.