Extraction of phenolic compounds and anthocyanin from black and purple rice bran (Oryza sativa L.) using ultrasound: A comparative analysis and phytochemical profiling

Abstract

The ultrasound-assisted extraction (UAE) of phenolic compounds and monomeric anthocyanin from black and purple rice bran was modeled and optimized in this study. The process of extraction was optimized using four variables rotatable central composite design (RCCD) followed by response surface methodology (RSM) to achieve improved total phenolic compounds (TPC) and monomeric anthocyanin content. The effect of pH, temperature, solvent concentration, and extraction time on extraction yield was examined. The comparative analysis of purple and black rice bran at the optimized conditions revealed higher monomeric anthocyanin (34.86mg C3G/L) and TPC (2232mg GAE/100g) in the purple rice bran extracts than black rice (31.95mg C3G/L and 1978.76mg GAE/100g). Moreover, the TPC and anthocyanin yield using UAE were significantly higher than the conventional extraction process for purple (778.98mg GAE/100g and 21.82mg C3G/L) and black rice bran (753.89mg GAE/100g and 18.75mg C3G/L), respectively. The prediction of extraction yield using Artificial Neural Network (ANN) was carried out successfully. GC–MS analysis of extracts showed the presence of nine compounds in purple rice bran extract and four in black rice bran extract. The HPLC analysis showed that α-Tocopherol (163.5 and 154.75μg/L), Cynanidin-3-glucoside (192.63 and 2.78μg/L), 4-Hydroxybenzoic acid (349 and 347μg/L) and Vanillic acid (101.72 and 152.76μg/L) were the predominant compounds in bran extracts.