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

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 (34.86 mg C3G/L) and TPC (2232 mg GAE/100 g) in the purple rice bran extracts than black rice (31.95 mg C3G/L and 1978.76 mg GAE/100 g). Moreover, the TPC and anthocyanin yield using UAE were significantly higher than the conventional extraction process for purple (778.98 mg GAE/100 g and 21.82 mg C3G/L) and black rice bran (753.89 mg GAE/100 g and 18.75 mg 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 alpha-Tocopherol (163.5 and 154.75 mu g/L), Cynanidin-3-glucoside (192.63 and 2.78 mu g/L), 4-Hydroxybenzoic acid (349 and 347 mu g/L) and Vanillic acid (101.72 and 152.76 mu g/L) were the predominant compounds in bran extracts. (C) 2016 Elsevier B.V. All rights reserved.