Philippine yam (Dioscorea spp.) tubers phenolic content and antioxidant capacity
2011
Cornago, D.F. | Rumbaoa, R.G.O. | Geronimo, I.M.
Five Philippine varieties of purple yam or ube (Dioscorea alata)-Daking, Kimabajo, Rapang-rapang, Sampero, and Shiket, and two varieties of lesser yam or tugui (Dioscerea esculenta)-Highland and Lowland, were analyzed in the study for phenolic content and anti-oxidant activity. The total phenolic content of the samples ranged from 69.9 to 421.8 mg gallic acid equivalent (GAE)/100 g dry weight. EC sub 50 values were 1.7-14.8, 6.2-31.7, and 17.5-35.1 mg/mL for radical scavenging activity, reducing power and iron chelating capacity, respectively. Total antioxidant activity by ferric thiocyanate method at 50 mg/mL was between 92.0-95.6%. All samples had better scavenging activity and reducing power on a ug analyte basis than alpha-tocopherol. Significant correlation was observed between total phenolic content and DPPH radical scavenging activity (R= -0.7664, P0.05) and reducing power (R0.05), for both purple yam and tugui. Significant correlation between total phenolic content and iron-chelating capacity was observed only for the tugui varieties (R= -0.9859, p0.05).
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