Effects of extraction solvents on antioxidant activities and total phenolic contents of four whole grains

The objectives of this study were to determine antioxidant activity and total phenolic contents (TPC) of the different solvent extractions (60% ethanol, 60% methanol, 60% acetone) from four whole grains, and to investigate relationships between antioxidant activities and TPC. The antioxidant activities of grain extractions were evaluated using the 1, 1-diphenyl-2- picrylhydrazyl radical (DPPH), 2, 2’-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium Salt (ABTS•+) and Ferric-ion reducing antioxidant power (FRAP) methods and the TPC were determined by Folin-Ciocalteu reagent (FCR). Results showed that extraction solvent mixtures had different impacts on antioxidant activity and TPC of whole grain varieties. For 60% acetone extraction, TPC hierarchy was as follows: buckwheat﹥barley﹥rye﹥oat; from which, the highest DPPH and ABTS•+ scavenging activities and reducing power were found in buckwheat. Furthermore, correlations analysis revealed that TPC, reducing power, DPPH and ABTS•+ scavenging activities were positively correlated with each other. Buckwheat could be important source of natural antioxidants to improve health conditions and to reduce disease risks.