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Green tea preparation and its influence on the content of bioactive compounds

The effect of different extraction conditions (tea form, water temperature, extraction time and multiple extractions) and storage time of prepared infusions on the content of phenolic compounds and methylxanthines of green teas and their antioxidant capacity were investigated. The content of total phenols, total flavonoids and total nonflavonids in green teas was determined spectrophotometricaly, while 7 flavan-3-ols, 6 phenolic acids and 3 methylxanthines were identified and quantified by using high performance liquid chromatography coupled with photodiode array detection (HPLC-PDA). In order to determine the antioxidant capacity of teas the 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging and ferric reducing/antioxidant power (FRAP) assays were applied. All tested green teas present a rich source of bioactive compounds, which extraction efficiency depends on extraction conditions. The findings of this investigation suggest that maximum extraction efficiency of studied bioactive compounds from green tea is achieved during aqueous extraction at 80°C, for 5´(powder), 15´(bagged) and 30´ (loose leaf). Regardless of the extraction conditions all green teas exhibited significant antioxidant capacity in vitro, which confirmes that green tea is one of the best dietary source of antioxidants. Antioxidant capacity of all tested teas was in correlation with their phenolic content, depending on the extraction conditions.

antioxidant capacity; bioactive composition; green tea; HPLC; preparation

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