Ethnopharmacological Value and Biological Activities via Antioxidant and Anti-Protein Denaturation Activity of Morinda lucida Benth and Momordica charantia L. Leaves Extracts from Benin

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 study aimed to appreciate the ethnopharmacological knowledge and evaluate the antioxidant and anti-inflammatory effects of M. charantia and M. lucida leaves extracts. Semi-structured surveys supported by individual interviews were conducted with herbalists and traditional healers in southern Benin. The antioxidant activities were evaluated by a micro-dilution technique using ABTS and FRAP methods. These activities were supported by cyclic voltammetry analysis. The anti-inflammatory activity was evaluated by the albumin denaturation method. The volatile compounds were analysed by GC-MS analysis. All the respondents involved in this study have good knowledge of the two plants. We identify 21 diseases grouped into five categories of condition. The two plants’ extracts possess variable antioxidant capacity. Indeed, all the active extracts of M. charantia presented an IC(50) < 0.078 mg/mL, while the extracts of M. lucida had an IC(50) up to 0.21 ± 0.02 mg/mL. For anti-inflammatory activity, a dose-response activity (p < 0.001) was observed in the protein denaturation inhibition rate of the extracts. It should be noted that the highest inhibition rate (98.34 ± 0.12) of the albumin denaturation was observed with M. lucida dichloromethane extract. A total of 59 volatile compounds were identified by GC-MS analysis in the extracts of the two plants. The M. charantia ethyl acetate extract shows the presence of 30 different compounds with a relative abundance of 98.83%, while that of M. lucida shows 24 compounds with a relative abundance of 98.30%. These plants are potential candidates to discover new compounds with therapeutic properties that could be used to solve public health problems.