Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 14, 2001
Publication Date: June 1, 2002
Technical Abstract: Phenolic compounds have free-radical scavenging properties and therefore are considered to be antioxidants. Phytochemicals with antioxidant activity may be protective against cardiovascular disease and cancer. Methanolic extracts of rice bran from sixteen rice varieties differing in bran color were examined for total phenolic content and antiradical efficiency against the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). Total phenolics were measured using the Folin-Ciocateu reagent and the antiradical efficiency was determined by calculating the reduction of the absorbance of a 25 ppm DPPH methanolic solution during the time reaction with the extracts, measured at 515 nm. The entries were extremely diverse for total phenolic contents ranging from 3.5 to 65.3 mg of gallic acid equivalent per g bran (mg GA eq./g). The white, light brown and speckled brown bran lines showed quite similar low phenolic contents (mean= 4.7 mg GA eq./g), whereas those with darker bran showed a greater range in phenolic concentration. Specifically, two genotypes with brown bran had 5.3 and 65.3 mg GA eq./g, and two with purple bran had 3.8 and 18.7 mg GA eq./g. The antiradical efficiency was highly correlated with total phenolics (r2= 0.99), even when the lines displaying low phenolic contents were considered seperately (r2= 0.67). The results indicate that phenolics are one of the primary groups of compounds in rice bran responsible for its free radical-scavenging activity.