Bioactivity and Nutritional Values of Some Dioscorea Species Traditionally Used as Medicinal Foods in Bandundu, DR Congo

Aims: To valorize traditional foods of the Democratic Republic of Congo in general and the province of Bandundu in particular by evaluating the antioxidant activity of five species of Dioscorea, the determination of their chemical composition as well the determination of their glycemic index.

Study Design: Survey; plant collection and identification, phytochemical and biological evaluation: phytochemical screening, proximate analyses, in vitro and in vivo assays.

Place and Duration of Study: “Université de Kinshasa” (DR Congo), from February 2013 to December 2015.

Methodology: The anti-diabetic activity was carried out in vivo using an animal model (NMRI mice), by administration of a solution of glucose (200 mg/mL). Antioxidant activity was evaluated using the ABTS and DPPH assays. The micrographic analysis of the flours of the studied species showed that their starch grains are characteristic of each species by their size, their form and the position of the hila and the presence of the scratches.

Results: All extracts of Dioscorea displayed highest ABTS and DPPH radical-scavenging activities (IC50<1 mg/mL) related to their appreciable amount of total phenolic contents. Total phenolic contents expressed as mg of gallic acid equivalent per gram of dried extract are ranged from 9.85±0.098 to 51.12±0.500. Only Dioscorea bulbifera contains flavonoids expressed as 3.33±0.23 mg of quercetin equivalent. These yams showed a good antihypergycemic activity, Dioscorea praehensilis and Dioscorea bulbifera showed a glucose reduction rate of 54.0% and 51.3% after 30 min respectively.

Conclusion: The results obtained show that Dioscorea tubers species studied have a high food value and thus can be developed as functional food.