Chemical evaluation of wild under-exploited Vigna spp. seeds

Eight wild Vigna spp. (Vigna vexillata, Vigna vexillata macrosperma, Vigna luteola, Vigna oblongifolia, Vigna unguiculata dekindtiana, Vigna racemosa, Vigna reticulata, Vigna ambacensis) were analysed for chemical characteristics (protein, amino acid profile, starch digestibility) and for antimetabolic compounds, such as trypsin inhibitors, cysteine proteinase inhibitors, lectins, phytic acid and tannins, in order to find useful material for improving the resistance and nutritional aspects of cowpeas. V. vexillata showed a high protein content of up to 293 g kg−1, whereas all the accessions had high sulphur amino acids (2.05-3.63 g per 16 g N) and consequently a high chemical score. Moreover, the level of resistant starch was also high (64–75%). A wide variability was found in the trypsin inhibitors, tannins and lectins; V. luteola contained high levels of these compounds, whereas V. unguiculata dekindtiana, V. reticulata and V. ambacensis had very low levels. Significant positive correlations were found between bruchid resistance and trypsin inhibitor, tannin and resistant starch content.