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Abstract

Context and aim:The présent study is the contribution in the valorization of local traditional foods of current consumption in Kinshasa in particular and in Democratic Republic of Congo in general.It has as aim to assess the phytochemical and antioxidant activities of the total polyphenolic extracts of tubers of two yams, Dioscorea alata and D. rotundata.Methodology and Results : The content of polyphenolic compounds has been measured in using the antioxidant Folin Ciocalteu's reagent assay.The antioxidant activity of total extracts of two yams has been measured by the percentage of inhibition of DPPH radical.It comes out of this study that the extraction production is respectively 20.5 and 12.9% for Dioscorea alata and D. rotundata.Furthemore, the recorded contents of the total polyphenolic compounds are: 3,888±0,346mgGAE/g DM (dry matter) for Dioscorea alata and 30,166±1,877mgGAE/g DM for D. rotundata.The rapports in flavonoids and tannins are equally different between two plants.The variance analysis (ANOVA 1) and the Turkey test indicated that the difference is significant on probability sill α= 0.05 (p<0,05).However, it has not significant difference in the antioxidant activity realesed by the total extract coming from two yams species (p>0.05); the two plants having both presented a good antioxidant capacity (IC50 ≤ 1 mg/mL).A positive correlation was observed between concentrations coming from different prepared dilutions and inhibition rate of DPPH radical by the extracts of plants (The correlation coefficient R 2 close to 1). Conclusion and application of results:The presence of the phenolic compounds makes these yams a nutraceutic to valorize.They can thus be developped and daily used as functional food for the population.