Comparative Study of the Chemical Constituents of Edible and Saponin Bearing Dioscorea Tubers

Tubers of three saponin bearing species of the genus Dioscorea (D. composite/, D. deltoidea and D. floribunda) and two edible species (D. alata and D. esculenta) were analysed for certain chemical and mineral constituents, β-amylase activity was also studied. The saponin bearing species as a group are quite distinct chemically in some aspects from the two edible species studied. The amounts of total carbohydrates, crude protein and tannins was higher in the two edible species. The edible species had lower β-amylase activity. The saponin bearing species had higher phosphorus and potassium contents. This group of species showed a higher concentration of soluble amino acids. The pattern of amino acids and non volatile organic acids in the two groups of species was similar. Citric and malic acids were identified in all the species. The data on sugars gave no definite pattern of distribution to contrast the edible from the saponin bearing species.