Comparative study on conventional, accelerated solvent extraction and ultrasonic-assisted extraction of total phenolic and anthocyanin contents and antioxidant activities from Riceberry bran

Abstract

Importance of the work: The majority of phenolic compounds in cereals is bound to cell wall components, making extraction challenging.
Objectives: This study compared three extraction methods: accelerated solvent extraction (ASE), conventional solvent extraction (CSE) and ultrasonic-assisted extraction (UAE).
Materials & Methods: The total phenolic and anthocyanin contents of the Riceberry bran (RBB) extracts were evaluated using the Folin-Ciocalteu and pH differential methods. Antioxidant activities were determined using ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-1picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. The phenolic acids and anthocyanins contents of the extract were detected using high performance liquid chromatography (HPLC).
Results: The optimal conditions for each method were: CSE, UAE (80°C for 15 min) and ASE (80°C for 5 min). Comparing the optimal condition among the three methods, ASE had mean values for the total phenolic content (TPC) and total anthocyanin content (TAC) of 19.70 ± 0.68 mg gallic acid equivalents/g RBB and 88.54 ± 0.57 mg/100g RBB, respectively. The FRAP value, %scavenging activity of DPPH and ABTS of the ASE extract were 85.06 ± 0.28 μmol/g RBB, 57.94 ± 0.31 and 26.39 ± 0.27, respectively. Significant differences (p < 0.05) in the amounts of phenolic acids and anthocyanins in the extract depended on the extraction method. The ASE and UAE extracts had the highest amount of vanillic acid, cyanidin 3-glucoside and total bioactive compounds that were significantly different from the CSE method.
Main Finding: The ASE method could be more appropriate for the extraction of total phenolic and anthocyanin contents as it had the highest levels of TPC and TAC efficiency.