ABSTRACT
Objective:To investigate the free radical scavenging,antidiabetic,kinetics of enzyme inhibition and cytotoxic potentials of flavonoid-rich extract of Gazania krebsiana leaves using standard methods.Methods:Antioxidant activity of the flavonoids was investigated at scavenging free radicals such as 1,1-diphenyl-2-picryl hydrazyl,nitric oxide,hydroxyl radical,reducing capabilities,2,2-azinobis (3-ethylbenzothiazoline-6) sulphonic acid as well as metal chelating capability at different concentrations (125-1 000 μg/mL) while the antidiabetic activity was evaluated via the inhibition and kinetics of carbohydrate digestive enzymes including α-αmylase,α-glucosidase,sucrase and maltase.Brine shrimp lethality assay was also employed to examine the cytotoxic effects at various concentrations (125-2 000 μg/mL).Results:The study showed the best antioxidant activity in 2,2-azinobis (3-ethylbenzothiazoline-6)sulphonic acid,hydroxyl radical,nitric oxide and metal chelating with IC5o values of (1 089.00±19.29),(719.40±5.35),(633.10±5.31),(1 116.00±22.92) μg/mL,respectively;as compared with butylated hydroxyl anisole (standard) with IC50 of 1 166,747,639 and 1 363 μg/mL,respectively.Similarly,strong inhibition of α-glucosidase as well as moderate inhibition of sucrase and maltase enzyme activities which were significantly (P＜0.05) better than acarbose were also observed in the study;though acarobse activity against α-amylase was better than the extract.The kinetics or mode of inhibition of α-amylase by the extract revealed an uncompetitive inhibition,competitive for α-glucosidase and non-competitive inhibitions for both sucrase and maltase,while the result of the lethality assay showed a potent cytotoxic effect with LC50 value of 359 μg/mL.Conclusion:The results obtained from this study are suggestive of the antioxidative,antidiabetic and cytotoxic potentials of flavonoid-rich extract of Gazania krebsiana.