ANTIOXIDANT EVALUATION AND PHYTOCHEMICAL CONTENT OF VARIOUS RICE BRAN EXTRACTS OF THREE VARIETIES RICE FROM SEMARANG-CENTRAL JAVA, INDONESIA

摘要

Objectives : The objectives of this research were to 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 EC 50 of FRAP and IC 50 of DPPH antioxidant activities. Methods : Extraction was conducted by reflux using different polarity solvents. The extracts were evaporated using rotary evaporator. Determination of total phenolic, flavonoid and carotenoid content, antioxidant activities using FRAP and DPPH assays were performed by UV-visible spectrophotometry and its correlation with EC 50 of FRAP capacities and IC 50 of DPPH scavenging activities were analyzed by Pearson’s method. Results : Ethanolic rice bran extract of black rice showed the lowest EC 50 of FRAP capacity 64.35 μg/ml and IC 50 of DPPH scavenging activity 23.92 μg/ml. The highest phenolic content, flavonoid content and carotenoid content were also given by ethanolic rice bran extract of black rice. There were significantly negative correlation between total phenolic content and carotenoid content in rice bran extract of red rice and black rice with their IC 50 of DPPH. Conclusions : All of rice bran extracts (except n-hexane rice bran extract of black rice and ethanolic rice bran extract of white rice) were very strong antioxidant, by DPPH assay. Phenolic and carotenoid compounds in rice bran extracts of red rice and black rice were the major contributor in antioxidant activity by DPPH assay. Rice bran extracts of black rice had linear results by FRAP and DPPH assays.