Bioactive compounds and antioxidant properties of different solvent extracts derived from Thai rice by-products

We investigated the contents and compositions of bioactive compounds in by-products of rice as affected by extraction with different solvents. Free and bound phenolic compounds and their antioxidant activities of rice bran and husk extracted by acetone, ethanol, and water at different temperatures (50, 60, 70, and 80 degrees C) were evaluated. Overall, the heated water extract provided the highest 2,2-diphenyl-1-picrylhydrazyl radical scavenging activities, ferric-reducing antioxidant power, total phenolic content, and total flavonoid content compared to the other solvents of all the samples studied. The antioxidant activities increased when the water temperature increased from 50 to 70 degrees C but decreased at 80 degrees C. The contents of bound phenolics were greater than those of free phenolics, including phenolic acids and flavonoids, in all the samples studied. Acetone gave the highest amounts of gamma-oryzanol and tocopherols in all samples. With a reduction in particle size of the rice husk, there was a significant increase in extracted phenolic acids, flavonoids, and antioxidant properties.