Three Varieties Rice from Central Java- Indonesia: Rice Bran Potential as Antioxidant

This chapter evaluate antioxidant activity from different polarities rice bran extract of three varieties of rice using two methods of antioxidant testing which were FRAP (Ferric Reducing Antioxidant Power) and DPPH (2,2-diphenyl-1-picrylhydrazyl), and correlation of total phenolic, flavonoid and carotenoid content with their EC50 of FRAP and IC50 of DPPH antioxidant activities. Rice bran is a rich source of natural antioxidants which can be used as free radical scavengers. It is widely recognized that many of the today’s diseases are due to the oxidative stress that results from an imbalance between formation and neutralization of free radicals. Reflux extraction was carried out with various polarity solvents. A rotary evaporator was used to evaporate the extracts. By utilising UV-visible spectrophotometry, the total amount of phenolic, flavonoid, and carotenoid content was determined. Antioxidant activities were assessed using the FRAP and DPPH tests, and their association with the EC50 of FRAP capacities and the IC50 of DPPH scavenging activities was examined using Pearson's method. Ethanolic rice bran extract of black rice showed the lowest EC50 of FRAP capacity 64.35 g/ml and IC50 of DPPH scavenging activity 23.92 g/ml. Present research exposed that EC50 of FRAP capacities and IC50 of DPPH scavenging activities of various rice bran extracts from three varieties rice in the range of 64.35 - 387.90 g/ml and 23.92 - 143.59 g/ml, respectively. FRAP and DPPH assays have the same mechanism reaction which is electron transfer. Electron transfer in DPPH assay, including ability to scavenge free radical of DPPH, meanwhile in FRAP assay depend on reduction potential of sample The highest phenolic content, flavonoid content and carotenoid content were also given by ethanolic rice bran extract of black rice. There were significantly negative correlations between total phenolic content and carotenoid content in rice bran extract of red rice and black rice with their IC50 of DPPH. By DPPH assay, all rice bran extracts were extremely potent antioxidants, with the exception of the n-hexane rice bran extract of black rice and the ethanolic rice bran extract of white rice. Red and black rice bran extracts' phenolic and carotenoid components were the main source of the antioxidant activity measured by the DPPH experiment. DPPH and FRAP methods showed linear result in antioxidant activities of rice bran extracts of black rice. Rice bran of red and black rice had potential to be developed as natural antioxidant sources.