Oxidative stress mitigation, kinetics of carbohydrate-enzymes inhibition and cytotoxic effects of flavonoids-rich leaf extract of Gazania krebsiana(Less.): An in vitro evaluation

摘要

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/m L) while the antidiabetic activity was evaluated via the inhibition and kinetics of carbohydrate digestive enzymes including α-amylase, α-glucosidase, sucrase and maltase. Brine shrimp lethality assay was also employed to examine the cytotoxic effects at various concentrations(125-2 000 μg/m L). 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 IC50 values of(1 089.00±19.29),(719.40±5.35),(633.10±5.31),(1 116.00±22.92) μg/m L, respectively; as compared with butylated hydroxyl anisole(standard) with IC50 of 1 166, 747, 639 and 1 363 μg/m L, 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 acarbose 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/m L. Conclusions: The results obtained from this study are suggestive of the antioxidative, antidiabetic and cytotoxic potentials of flavonoid-rich extract of Gazania krebsiana.