Green extraction of anthocyanins from Syzygium cumini fruit pulp using aqueous glycerol through ultrasound-assisted extraction

Abstract

Aqueous glycerol is a proposed green extractant for anthocyanins and polyphenols as an alternative to conventional solvents. The aim of this study was to investigate the potential use of aqueous glycerol to extract anthocyanins from Syzygium cumini fruit pulp with high yields. The ultrasound-assisted extraction process was also examined to enhance the extraction yield. The application of ultrasound-assisted extraction along with glycerol as a modifier remarkably enhanced the extraction of anthocyanins compared to the conventional extraction. Aqueous glycerol (70%) was screened against conventional solvents (ethanol, methanol and water), where glycerol showed promising outcomes. The optimised ultrasonication time and extraction temperature (25 °C for 5 min) were selected based on our previous study of NADESs. The results showed that glycerol gave the highest amount of anthocyanin content (201.05 mg C3G/100 g fresh weight) compared to conventional solvents for retrieving anthocyanins from S. cumini fruit pulp. Besides the anthocyanin content, the extract yield, phenolic content, and antioxidant activities using DPPH and FRAP were also determined. Glycerol showed a higher phenolic recovery (0.9 mg GAE/g dry sample), resulting in higher antioxidant activity (DPPH activity-73.35% inhibition). Therefore, the application of UAE with aqueous glycerol provides accessibility and enhanced anthocyanin extraction efficiency, thus fulfilling the green and sustainable approach to anthocyanin extraction.