Negative pressure cavitation-microwave assisted preparation of extract of Pyrola incarnata Fisch. rich in hyperin, 2′-O-galloylhyperin and chimaphilin and evaluation of its antioxidant activity

A novel and effective extraction method, namely negative pressure cavitation-microwave assisted extraction technique (NMAE), was developed for the preparation of extracts of Pyrola incarnata Fisch., which are rich in the main constituents hyperin, 2′-O-galloylhyperin and chimaphilin. Single factor experiments and Box–Behnken design (BBD) were combined with a response surface methodology to examine factors affecting extraction. Maximum extraction yields of hyperin, 2′-O-galloylhyperin and chimaphilin (1.339 ± 0.029, 4.831 ± 0.117 and 0.329 ± 0.011 mg/g, respectively) were achieved under the following optimised conditions: 700 W microwave power, 50 °C extraction temperature, 30:1 mL/g liquid–solid ratio, −0.05 MPa negative pressure, 55% ethanol concentration and 12 min extraction time. First-order kinetics equation demonstrated that NMAE offered significant savings in extraction time, and enhancing extraction efficiency. Furthermore, NMAE extracts yielded excellent antioxidant activity (IC50 0.121 mg/mL for DPPH 2.896 mmol FeSO4/g DW FRAP).