Four fractions, namely, rice bran, rice husk, brown rice and milled rice of a Thai rice variety (Khao Dawk
Mali 105), collected from three different growth sites, were analysed to determine phenolic acid composition,
c-oryzanol and tocopherols content and their antioxidant capacity using the 2,2-diphenyl-1-picrylhydrazyl
(DPPH) radical scavenging and ferric reducing ability power (FRAP) assays. The bran and
husk fractions showed higher values of antioxidant activity based on the DPPH and FRAP assays, compared
to the other fractions. In addition, the bran fraction had the highest c-oryzanol and tocopherols
content. On the other hand, the husk fraction showed a greater phenolic acids concentration than the
other fractions. The three major phenolic acids found in all fractions, despite different growth sites, were
ferulic, vanillic and p-coumaric acids. Ferulic acid was most evident in the bran, whereas vanillic and
p-coumaric acids were mostly found in the husk. Significant differences (p < 0.05) in the antioxidant
capacities of each fraction depended on the growth sites and antioxidant components. We propose that
variation in phenolic acid content could be affected by the growth sites. This study demonstrates that rice
bran and husk can be considered as valuable sources of bioactive components with high antioxidant
properties.