The total antioxidant activity (TAA) and trypsin inhibition activity (TIA) of storage protein dioscorin from six yam cultivars (Dashan, Hualien No. 3, Keelung, Mingchien, Tainong No. 2, and Japanese yam) were demonstrated. Japanese yam had the highest TAA and the lowest calculated EC50 at any purification stage. Following gel permeation, dioscorins purified from Hualien No. 3 and Japanese yam showed the highest TIA and lowest calculated IC50. Dioscorin with higher TIA apparently possesses better TAA. The pIs of dioscorin from all yam species were in the range of 5.94–4.33 indicating acidic protein in nature. Results from isoelectric focusing chromatography showed regardless of species higher TIA for dioscorin eluted at lower pH.