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

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.

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.

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.

TBL is an important source of antidiabetic, antimicrobial and antioxidant agent.