Comparative In Vitro Evaluation of the Antidiabetic Potential of Morinda lucida and Ficus capensis Leaf Extracts

Oxidative stress and rapid postprandial hyperglycaemia are central features of diabetes mellitus, and plant extracts that scavenge free radicals and inhibit the carbohydrate-digesting enzymes α-amylase and α-glucosidase are of interest as sources of antidiabetic agents. Morinda lucida and Ficus capensis are tropical African medicinal plants with reported antidiabetic uses, but their in vitro activities have not been compared directly under the same conditions. Ethanolic leaf extracts of both plants were evaluated for total phenolic content (TPC; Folin–Ciocalteu), total flavonoid content (TFC; aluminium chloride), DPPH radical-scavenging activity (62.5–1000 µg/mL), ferric reducing antioxidant power (FRAP), and α-amylase and α-glucosidase inhibition, with acarbose as the reference inhibitor. IC50 values were estimated by nonlinear regression. F. capensis had higher TPC (≈240 versus ≈85 µg GAE/mg) and TFC (≈123 versus ≈101 µg QE/mg) than M. lucida. DPPH scavenging at 1000 µg/mL was 77.98 ± 0.33% for F. capensis versus 30.37 ± 0.62% for M. lucida, and FRAP was ≈95 versus ≈20 µg TE/mg. F. capensis showed stronger α-amylase inhibition (IC50 ≈110 versus ≈500 µg/mL; acarbose ≈90 µg/mL) and a slightly lower α-glucosidase IC50 (≈230 versus ≈250 µg/mL; acarbose ≈100 µg/mL). Under the conditions tested, the ethanolic leaf extract of F. capensis showed the stronger antioxidant and carbohydrate-digestive-enzyme inhibitory profile, particularly against α-amylase, whereas M. lucida showed weaker but measurable activity. These in vitro findings support further bioassay-guided and in vivo investigation of both plants as sources of antidiabetic constituents.