Free and bound phenolic profiles and antioxidant activity of milled fractions of different indica rice varieties cultivated in southern China

•Free & bound antioxidant phenolics in endosperm and bran of indica rice investigated.•Phenolic content and antioxidant activity of bran/embryo mainly exist in free form.•The endosperm fraction contains both free and bound forms of phenolics.•Bran/embryo fraction contributes most to phenolics content and total antioxidant activity.•Ferulic and coumaric acid in bound forms were distributed mainly in bran/embryo. This study quantified free and bound phytochemicals and their antioxidant activity in the endosperm and bran/embryo of different indica rice varieties. Phytochemicals mainly existed as free form in the bran/embryo and as both free and bound forms in the endosperm. The average values of total phenolic content, flavonoid content, FRAP, ABTS and ORAC values in the bran/embryo were 3.1, 10.4, 8.2, 11.2 and 11.4 times higher than those in the endosperm, respectively. In whole brown rice, the bran contributed 59.2%, 53.7%, 47.7%, 55.5% and 56.9% of total phenolics, flavonoids, FRAP, ABTS and ORAC values, respectively. Seven individual phenolics (gallic, protocatechuic, chlorogenic, caffeic, syringic, coumaric and ferulic acids) were detected with most coumaric and ferulic acids in the bran. All measurements exhibited varietal differences. These findings provide important information for improving human health by encouraging the consumption of whole brown rice and its use in food product development.