Background: Momordica charantia Linn. (Cucurbitaceae), the wild variety of bitter melon and Morinda lucida Benth (Rubiaceae) were commonly used as a popular folk medicine in Benin. This research focused to measure the antioxidant and enzyme inhibitory effects of M. charantia and M. lucida leaves and their antidiabetic activity.
Methods: Antioxidant activities were evaluated by micro-dilution technique using DPPH free radical scavenging activity and β-carotene-linoleate bleaching assay. The α-amylase inhibition assay was carried out utilizing the 3,5-dinitrosalicylic acid procedure, while β-glucosidase inhibition assay was demonstrated using as substrate p-nitrophenyl-β-D-glucopyranoside (PNPG). HPLC-DAD analysis was realized using a high-performance liquid chromatography systems with diode-array detector, L-3000.
Results: Chlorogenic acid, epicatechin, daidzein, rutin, naringin, quercetin, naringenin and genistein were identified as polyphenol compounds in the both plants extract. Dichloromethane and ethyl acetate extracts showed a good α-amylase inhibitory activity (56.46 ± 1.96% and 58.76 ± 2.74% respectively). M. lucida methanolic extract has shown IC50 of 0.51 ± 0.01 mg/mL, which is the lowest for DPPH scavenging activity. M. lucida dichloromethane extract showed the highest inhibitory capacity of β-glucosidase activity (82.11. ± 2.15%).
Conclusion: These results justify some traditional medicinal uses of both plants. The purified fractions could be used in future formulations, possibly incorporated in functional foods to combat certain diseases.
Keywords: Benin; DPPH; HPLC; antioxidant; diabetes mellitus; plant extracts; β-Carotene–linoleate bleaching.