Purification, identification, and in vitro antioxidant activities of selenium-containing proteins from selenium-enriched brown rice

Selenium-enriched brown rice (Se-BR) has been reported to accumulate Se mainly in its proteins. Purification of selenium-containing proteins (Se-Ps) from Se-BR and their in vitro antioxidant activities were investigated in this study. Sephadex G-100 gel filtration and diethylaminoethyl cellulose Sepharose Fast Flow anion-exchange chromatography were used to purify the major Se-Ps from the crude protein extract from Se-BR. Se content was measured after each step to determine the major Se-containing fraction for further separation. Three major Se-Ps with molecular weights of similar to 15 kDa, determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis, were isolated and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Their antioxidant activities were evaluated using three different free radical-scavenging assays, namely, the hydroxyl radical-, superoxide anion-, and 1,1-diphenyl-2-picrylhydrazyl-scavenging assays. Results indicate that Se-Ps purified from Se-BR exhibit antioxidant activities and may be used as potential antioxidants.