Abstract:

The phenolics in brown rice were purified with liquid extraction, macroporous resin method and solid phase
extraction method, respectively. The recovery of polyphenol and antioxidant activity were studied. The recoveries of total
phenolic acids and nine individual compounds were analyzed by HPLC. The recoveries of polyphenols purified with the
above purification methods were 20.51%, 53.45% and 87.87%, respectively, whereas the recoveries of total phenolic acids
with the three purification methods were 56.84%, 67.35% and 68.99%, respectively. The purity of polyphenols from brown
rice was increased from 19.23% to 40.72%, 46.84% and 78.71%, respectively. Polyphenol content displayed significant
correlations with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability and ferric reducing ability of plasma
(FRAP) (P < 0.01). Except for the rice varieties, the purification methods resulted in a large difference in the phenolic
content by influencing the recovery of non-phenolic acid polyphenols. The purification methods had a significant influence
on the recovery of phenolic acids. Thus, the appropriate method should be chosen by recovery of the targets but not by the
recovery of total polyphenols or total phenolic acids.

Key words: brown rice, polyphenol, purification, high performance liquid chromatography (HPLC)