RÉSUMÉ
For many years, medicinal plants have been a resource for healing in several local communities around the world and the phytochemicals in them such as flavonoids, alkaloids, phenolic, tannins, and terpenoids are attributed to their many medicinal values. Vernonia amydalina, Senna alata, Jatropha curcas, and Grewia pubescens are important plants with immense value. In this study, phytochemical screening, antioxidant analysis and the potential anti-hyperglycemic properties of the plants was investigated in-vitro. The ethanol leave extracts of the plants were subjected to qualitative phytochemical screening and tannin, flavonoids and phenol quantification. Ferric reducing antioxidant power and DPPH radical inhibition of the extracts was done by spectrophotometric method while the anti-diabetic potential was analyzed through the in-vitro ?-amylase and ?-glucosidase inhibition. Phytochemicals detected in the ethanol leave extracts of the four plants are tannins, flavonoids, phenolics, terpenoids, steroids, alkaloids, cardiac glycosides, and saponins. Flavonoids, phenols, and tannin content were highest in Senna alata (0.27±0.0.002 mg: mg of rutin per g of extract, 10.63±0.0.017 mg: mg of gallic acid per g of extract, and 6.72±0.06 mg/g respectively) followed by V. amygdalina (0.20±00.002 mg: mg of rutin per g of extract, 8.27±0.0.017 mg: mg of gallic acid per g of extract, and 7.98±0.03 mg/g respectively). While the least content of all was found in the extracts of Jatropha curcas. Concentration dependent and statistically significant difference was observed in both the FRAP and DPPH radical inhibition of all the extracts. Senna alata showed the strongest reducing power followed by the V. amygdalina. Both Senna alata and V. amygdalina showed DPPH radical inhibition that is not significantly (p>0.05) different from that of trolox. ?-amylase and ?-glucosidase inhibition was also demonstrated in a concentration dependent manner. In both the ?-amylase and ?-glucosidase inhibition, V. amygdalina and S. alata exhibited the most significant inhibitory properties among the plant extracts. The overall result in this study suggested that V. amygdalina, S. alata with the highest content of the phytochemicals, and antioxidant activities are potential source of antioxidant constituents and might be useful for the management of diseases such as diabetes.