Antidiabetic, antioxidant and antimicrobial activities of extracts of Tephrosia bracteolata leaves

Aims: Plant extracts have long been used for the ethnomedical treatment of diabetes, microbial infections and as a source of antioxidant. This study was aimed at investigating the antidiabetic, antioxidant, and antimicrobial activities of the n-hexane and ethyl acetate extract of Tephrosia bracteolata leaves (TBL) as associated with the ethnobotanical knowledge of the local people of Nigeria. Main methods: The phytochemical composition of the n-hexane and ethyl acetate extract of the leaves of T. bracteolata were determined following standard procedures in literature, and it's in vitro inhibitory activities against α-glucosidase enzyme. 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS.+) and 1,1-diphenyl-2-picrylhydrazyl (DPPH+) antioxidant activities were also examined. Well diffusion method was employed in evaluating the antimicrobial property of the extracts. Key findings: The ethyl acetate extract of T. bracteolata leaves had the greatest inhibitory effect on α-glucosidase, followed by the n-hexane with IC50 43.95 μg/ml and IC50 ˃50 μg/ml respectively. The ethyl acetate also exhibited significant DPPH+ and ABTS.+ antioxidant activity with IC50 of 24.96 μg/ml and 6.48 μg/ml as compared to Ascorbic acid and Trolox (12.24 μg/ml and 5.91 μg/ml) respectively. The zones of inhibition of the ethyl acetate extract of T. bracteolata leaves ranges from 10 – 25 mm at a concentration of 6.25–200 mg/ml, and it showed a greater antibacterial activity than the n-hexane extract, having a zone of inhibition from 10 – 20 mm at concentration of 12.5–200 mg/ml when compared to the standard Gentamycin. Similarly, the ethyl acetate extract of T. bracteolata showed a better anti fungi activity at concentration range 12.5–200 mg/ml than the n-hexane extract at concentration range of 25–200 mg/ml with reference to Tioconazole. These results indicated for the first time that the ethyl acetate extract of T. bracteolata leaves extracts exerted potent inhibitory effects against α-glucosidase, actively scavenge DPPH+ and ABTS.+ free radicals and successfully inhibits the proliferation of Gram positive and Gram negative microorganism. Significance: TBL is an important source of antidiabetic, antimicrobial and antioxidant agent.