Microwave-assisted extraction of tea polyphenols and tea caffeine from green tea leaves

A microwave-assisted extraction (MAE) method is presented for the extraction of tea polyphenols (TP) and tea caffeine from green tea leaves. Various experimental conditions, such as ethanol concentration (0–100%, v/v), MAE time (0.5–8 min), liquid/solid ratio (10:1–25:1 ml g−1), pre-leaching time (0–90 min) before MAE and different solvents for the MAE procedure were investigated to optimize the extraction. The extraction of tea polyphenols and tea caffeine with MAE for 4 min (30 and 4%) were higher than those of extraction at room temperature for 20 h, ultrasonic extraction for 90 min and heat reflux extraction for 45 min (28 and 3.6%), respectively. From the points of extraction time, the extraction efficiency and the percentages of tea polyphenols or tea caffeine in extracts, MAE was more effective than the conventional extraction methods studied.