Antioxidant evaluation and phytochemical content of various rice bran extracts of three varieties rice from Semarang, Central Java, Indonesia

Abstract

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 ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH), and correlation of total phenolic, flavonoid and carotenoid content with their exhibitory concentration 50 (EC50) of FRAP and inhibitory concentration 50 (IC50) 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 was performed by ultraviolet-visible spectrophotometry and its correlation with EC50 of FRAP capacities and IC50 of DPPH scavenging activities was analyzed by Pearson’s method. Results: Ethanolic rice bran extract of black rice showed the lowest EC50 of FRAP capacity 64.35 µg/ml and IC50 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 was significantly negative correlation between total phenolic content and carotenoid content in rice bran extract of red rice and black rice with their IC50 of DPPH. Conclusions: All of the 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.