Antioxidant Activities of Mucilages from Different Taiwanese Yam Cultivars

The antioxident effects of crude mucilages (CM) and partially purified mucilages (PPM) from three different Taiwanese yam cultivars-including Dioscorea alata L. cv. Tainong 1 (Th1), Dioscorea alata L. cv. Tainong 2 (TN2), and D. alata L. var. purpurea (Roxb.) Ming-Jen (MJ)-were evaluated, including 1,1-diphenyl-2-picrylhy-drazyl (DPPH) radical, hydroxyl radical, and superoxide radical scavenging activities Electron spin resonance (ESR) spectrometry was used to measure hydroxyl radical scavenging activities. The IC50 stands for the concentration required for 50% scavenging activity. The IC50 of CM and PPM against DPPH radical was 0.329, 0.279; 0.547, 0.653; and 0.847, 0.631 mg/ml, respectively, for TN1, TN2 and MJ. The IC50 of CM and PPM against hydroxyl radical by spectrophotometry was 0.668, 1.146; 1.461, 1.096; and 0.946, 1.554 mg/ml, respectively, for TN1, 1N2 and MJ. The IC50 of CM and PPM against superoxide radical was 0.802, 0.368; 0.681, 0.258; and 0.086, 0.148 mg/ml, respectively, for TN1, TN2 and MJ. Using ESR to detect hydroxyl radicals, the IC50 of PPM against hydroxyl radical was 0.083, 0.47, and 0.004 mg/ml, respectively, for TN1, TN2 and MJ. The results demonstrated that different cultivars of yams exhibited different antioxidant ability, and the purification process was able to partially increase the antioxidant activity of the mucilage polysaccharide. Taken together, these results suggest that mucilage polysaccharides of the yam tuber might play an important role on antiradicals and antioxidants.