Evaluation of antioxidant and α-glucosidase inhibitory activities of some subtropical plants.

The antioxidant and α-glucosidase inhibitory activities of the methanolic leaf extracts of some subtropical plants were evaluated in the present study. Antioxidant activity was evaluated based on 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, reducing power, hydrogen peroxide and β-carotene bleaching assays. α-Glucosidase inhibitory activity and enzyme kinetics as well as the total phenolic content of the extracts were also investigated. Elaeocarpus sylvestris extract had the highest activities on all the antioxidant assays performed such as DPPH scavenging activity (IC50 12.7 ± 0.5 μg mL(-1)), reducing power (491.1 ± 6.3 mg QE g(-1) dry extract), hydrogen peroxide (IC50 65.6 ± 0.4 μg mL(-1)) and β-carotene bleaching assays (IC50 5.1 ± 1.9 μg mL(-1)). The total phenolic content of the E. sylvestris extract also had the highest values for gallic acid, quercetin and rutin equivalents (353.8 ± 28.6 mg GAE g(-1) dry extract; 294.9 ± 24.5 mg QE g(-1) dry extract; 663.0 ± 52.3 mg RE g(-1) dry extract, respectively). α-Glucosidase inhibition assay revealed that Distylium racemosum had the highest activity with an IC50 value of 22.6 ± 1.9 μg mL(-1). The results of the present study revealed the potencies of E. sylvestris, D. racemosum, Acer mono Maxim and Liquidambar styraciflua as alternative sources for antioxidants and α-glucosidase inhibitors.