Preparation and antioxidant activity of green tea extract enriched in epigallocatechin (EGC) and epigallocatechin gallate (EGCG).

The present study investigated effects of solvents, temperature, and duration on extracting efficiency of catechins from green tea by an orthogonal test. The results suggested that extraction of epigallocatechin gallate (EGCG) was highly dependent on these factors, whereas that of epigallocatechin (EGC) was significantly affected by duration and solvent (P < 0.05). Effects of these factors on epicatechin (EC), catechin (C), and epicatechin gallate (ECG) were not significant. A two-step preparation was adopted to produce green tea extract enriched in EGC (GTE-EGC) and green tea extract enriched in EGCG (GTE-EGCG). The optimum conditions for GTE-EGC were that green tea was brewed in 75% ethanol at 30 degrees C for 10 min, whereas for GTE-EGCG the same tea was brewed in 35% ethanol at 90 degrees C for 60 min. Compared with GTE-EGC, GTE-EGCG had EGCG increased by 110.42%, whereas EGC decreased by 40.38% with EC and ECG being unchanged. Most importantly, GTE-EGCG possessed greater antioxidant activity (in vitro) than GTE-EGC.