Evaluation of antioxidant activities and phenolic subtype contents of ethanolic bran extracts of Thai pigmented rice varieties through chemical and cellular assays

This study revealed that the ethanolic bran extracts of 11 Thai pigmented (red and purple) and 2 nonpigmented rice varieties exerted scavenging activity against DPPH and ABTS radicals and ROS in HL‐60 cells in the following order: red > purple > nonpigmented rice. These rice extracts also showed the same order of phenolic and flavonoid contents, which were strongly correlated with their scavenging activity. Phenolic subtype analysis further indicated that proanthocyanidins as well as anthocyanins and protocatechuic acid contributed directly to antioxidant capacity in red and purple rice bran, respectively. In contrast, these pigmented rice bran extracts possessed moderate chelating activity partly attributed to their contents of phenolics and flavonoids, especially proanthocyanidins in red rice bran. Moreover, rice bran extracts significantly restored SOD and CAT activities in oxidative stress‐induced A549 cells. This study provides new insights on the intracellular potent antioxidant capacity of pigmented rice bran extracts in the cell‐based systems.