Paper
Paper
This work aimed to develop a microwave-assisted extraction (MAE) method for green tea to efficiently extract catechins. Green tea was extracted with various solvent types, including water, 50 % ethanol–water, and 50 % acetonitrile–water, with a controlled microwave power of 250–800 W for 2–8 min of irradiation at a fixed temperature of 80 °C. Caffeine from the crude extract was separated by partitioning with chloroform, and catechins were separated using ethyl acetate. The HPLC results demonstrated that maximum yield of catechins (24.7 mg/g for EGC; 8.2 mg/g for C; 14.3 mg/g for EC; 39.6 mg/g for EGCG 14.5 mg/g for GCG and 21.7 mg/g DW tea for ECG) was obtained with a 50 % ethanol–water system at 500 W power within 6 min of treatment. The limits of detection and quantification were in the range of 0.15–0.56 and 0.30–1.23 µg mL−1, respectively. Satisfactory recoveries (0.8–2.7 %) and the intra-day and inter-day precisions (RSD% 1.63–3.84 % and 0.76 %–1.95 %, respectively) were found. The catechin components discovered in green tea included relatively high quantities of epicatechin gallate (ECG), (epigallocatechin gallate (EGCG), and epigallocatechin (EGC). The DPPH assay assessed the antioxidant activity of the various infusions prepared at different parameters. The results demonstrated high antioxidant activity (78.4–94.0 %) for the infusions extracted with the ethanol–water mixture at 500 W microwave power within 6 min of treatment, followed by the acetonitrile–water mixture. The antioxidant potentials of the extracts showed a linear correlation with the catechin contents in the extracts.