The analysis of quality and antioxidant activity of green tea extracts

The aim of the research was to analyze the composition of biologically active compounds, to determine the correlation between the concentration of biologically active compounds and antioxidant activity, the dependence of extractive compounds on the extraction time, the quality of different tea preparation forms (daily tea, infusions, decoctions) of those teas found in Lithuanian market. Four specimens of green tea from different regions of the world have been chosen as the object of analysis. Quality criteria's have been analyzed by using gravimetric and spectrophotometric methods. Detailed analysis has been performed using high performance liquid chromatography (HPLC) technique. With reference to analysis results it can be stated that in the aspect of relation to antioxidant activity/phenolic compounds, the teas with highest numbers in these dimensions were those from China region. The least numbers in antioxidant activity, dry residue and phenolic compounds were of teas from Sri Lanka. We tested the hypothesis that all green teas have phenolic compounds as their biological active compounds and because of this group of active compounds they distinguish antioxidant activity. The study gave strong evidence that green tea as a daily preparation and as well as pharmaceutical form (infusions, decoctions, capsules of green tea extract) may be used as preventive measures for cancerogenous processes, prostate cancer, renal or liver diseases because of it's antioxidant and free radical binding properties.