The effects of solvent–based ultrasonic–assisted extraction of bioactive compounds and antioxidant activities from pigmented rice bran

Abstract

Rice is one of the staple grains that most people consume. Pigmented rice is a highly nutritious rice bran, and it is abundant in bioactive compounds like phenolic compounds, which have antioxidant activities. In order to effectively extract bioactive compounds for adoption, it is essential to select the optimal solvent–based extraction method. The study's objective was to optimize the solvent–based ultrasonic–assisted extraction of bioactive compounds and antioxidant activities from pigmented rice bran. A single factor investigation was used to study the effects of duration time (20–40 min), UAE temperature (30–60 °C), and sample–to–solvent ratio (1:10–1:30 g/mL). The bioactive compounds were determined using total anthocyanin content (TAC), total phenolic content (TPC), and total flavonoid content (TFC) assays. The DPPH radical scavenging activity assay was used to assess antioxidant activities. According to the results of the experiments, extraction conditions had a significant effect on bioactive compound extraction and antioxidant activities. The optimum solvent extraction was 60% (v/v) aqueous methanol with 0.1% citric acid solvent, yielding values of 2.32 ± 0.14 mg C3G/g DW for TAC, 13.36 ± 0.89 mg GAE/g DW for TPC, 2.99 ± 0.87 mg QE/g DW for TFC and 398.29 ± 96.08 µg/mL for 50% inhibition concentration on DPPH (IC50). The ultrasonic–assisted extraction (UAE) of pigmented rice bran bioactive compounds under optimal conditions at 30 °C for 30 min with a material-to-solvent ratio of 1:20 g/mL resulted in an extract with 3.15 ± 0.15 mg C3G/g DW of TAC, 16.13 ± 0.82 mg GAE/g DW of TPC, 4.04 ± 0.11 mg QE/g DW of TFC and 413.90 ± 47.46 µg/mL of IC50. It shows that, under optimal conditions, solvent–based ultrasonic–assisted extraction could be used to maximize the extraction of bioactive phytochemicals from pigmented rice bran.