Microwave-assisted green extraction of antioxidant components from Osmanthus fragrans (Lour) flower using natural deep eutectic solvents

Abstract

Osmanthus fragrans (Lour) flower is a typical fragrant herb in eastern countries containing multiple bioactive compounds, the extract of which has been widely used as a natural antioxidant additive in food and cosmetics. However, the existing extraction methods use organic solvents during the extraction process, which is non-eco-friendly and harmful to human health. In this study, we introduce, to our knowledge for the first time, microwave-assisted deep eutectic solvent extraction (MA-DESE) to extract antioxidant components from O. fragrans flower. The MA-DESE procedure was optimised, validated, and compared with that of traditional solvent extraction by using response surface methodology. The maximum antioxidant activity of 101.81 mg Trolox equivalent/g of dry weight was achieved at the following optimum MA-DESE parameters: microwave power, 497.12 W; microwave treatment time, 59.03 s; and solid–liquid ratio, 31.14 mL/g. In addition, UPLC-MS analysis showed a greater variety of antioxidant components, such as olivil and osmanthuside H, in O. fragrans flower extract obtained by MA-DESE than by the traditional ethanol reflux method. These results demonstrated that MA-DESE, which is safe and eco-friendly, could substitute for the conventional solvent extraction process, which is time-consuming and tedious, for the extraction of antioxidant components from O. fragrans flower.