Phytochemical Composition, Antioxidant and In Vitro Enzyme-Based Antidiabetic Activities of Tulbaghia violacea Collected from the Eastern Cape and Gauteng Provinces, South Africa

Tulbaghia violacea, a plant native to Africa, is popular for its uses in traditional medicine, as well as in food and for household purposes. This study aimed to determine phytochemicals present in T. violacea, investigate the antioxidant and the enzyme-based antidiabetic activities in vitro, and identify potential differences in the activities depending on the growing environment of the plant. T. violacea leaves samples from two provinces in South Africa, viz. Gauteng (GP), an inland province and the Eastern Cape (EC), a coastal province were compared. The samples were extracted using maceration with hexane, acetone and methanol. Antioxidant activity was determined qualitatively and quantitatively with the DPPH radical scavenging assay, while the antidiabetic effects were determined using the α- amylase and α- glucosidase inhibition assays. The qualitative phytochemical screening revealed variable presence of saponins, flavonoids, tannins, alkaloids, steroids, cardiac glycosides and phenolics from both samples. The EC hexane extract showed the highest antioxidant activity (41,3%, IC50 68,3ug/ml). The GP and EC hexane extracts exhibited α-amylase inhibition of 85,5% (IC50= 9,02ug/ml ) and 85,7% (IC50= 15,03ug/ml) respectively, while the GP acetone extract showed α-glucosidase inhibition of 60,0% (IC50 = 42,2ug/ml). The findings elucidate on the antidiabetic mechanisms of T. violacea, showing in vitro α- amylase and α- glucosidase inhibitory activities and validate its ethnomedicinal use for diabetes.