pour le Développement au Tchad, ont fait l'objet d'une étude comparative de leurs teneurs en polyphénols et en antioxydants totaux. Les teneurs en polyphénols totaux ont été déterminées par la méthode utilisant le réactif du Folin-Ciocalteu et les teneurs en antioxydants ont été évaluées par trois méthodes courantes, simples et disponibles : Trolox Equivalents Antioxidant Capacity (TEAC), 1,1-Diphenyl-1-picrylhydrazyl (DPPH) et Ferric Reducing Antioxidant Power (FRAP). L'étude a montré que les polyphénols, responsables de la couleur des péricarpes contribuent à 94% à la teneur en antioxydants totaux des extraits étudiés. Ainsi, à travers les comparaisons effectuées, les 17 variétés suivantes ont été sélectionnées comme étant les plus riches en polyphénols (≤ 4,536 mg d'EAG/g) et en antioxydants totaux (≤ 10,72 mg d'ET/g ; FRAP
Momordica charantia L. (cucurbitaceae), is a plant whose fruits are widely consumed in Chad. Seeds, green and ripe pulps of the fruits of this plant were subject of this study. The total polyphenols, antioxidants, flavonoids and anthocyanins were evaluated by the Folin - Ciocalteu, DPPH, iron trichloride and pH-differential methods respectively. The total polyphenol obtained were 9.368 mg GAE/g for the seeds extract, 9.068 mg GAE/g for the green pulp extract and 8.505 mg GAE/g for the mature pulp extract. The total antioxidant were 2.351, 2.074 and 1.365 mg QE/g for seeds, green pulp and ripe pulp respectively. The total flavonoid was 0.818 mg QE/g for seeds, 0.812 mg QE/g for green pulp and 0.808 mg EQ/g for ripe pulp. The total anthocyanin for seed, green and ripe pulp extracts were 0.360, 0.318 and 0.238 mg/g, respectively. The results of the polyphenol assays of the samples after traditional culinary transformed, show that the thermal transformation has a negative impact which is characterized by a decrease in the polyphenol contents. Percentages of total polyphenols after culinary transformation were 11.28; 8.84 and 8.26% respectively for the extracts of green pulp, seeds and ripe pulp.
In order to make Mucuna seeds consumable, seeds are treated according to the following procedures: boiling, soaking followed by boiling in the presence of 0.5% KOH and finally soaking for a long time followed by boiling in the presence of 0.5% KOH, so that tannins can be removed. Preliminary studies done on the raw seeds of four Mucuna species revealed the presence of tannins.The results showed that the crushed seeds contained all high tannin with the content of 0.370 g GAE/100g DM, 0.336 g GAE/100g DM; 0.266 g GAE/100g DM and 0.203 g GAE/100g DM for Mucuna deerigiana, Mucuna nagaland, Mucuna cochinchinensis and Mucuna rajada respectively. The different methods of seed treatment significantly reduced the tannin content in Mucuna seeds. The method of soaking the seeds for 12 hours and then scalding in the presence of 0.5% KOH reduced tannins in Mucuna deerigiana, Mucuna nagaland, Mucuna cochinchinensis, and Mucuna rajada seeds by 47.29%; 48.21%; 66.16%; and 15.76% respectively. This method gave the highest tannin reduction rate.
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