Determination of the extraction frequency of green tea leaves by the antioxidant method

Aim. To determine the optimal extraction frequency of green tea leaves with 60 % ethanol by the antioxidant method. Materials and methods. Chun Myn green tea leaves were the object of the study, the raw material was collected in Anhui province (China) from March to April. Dry green tea leaves were standardized according to the European Pharmacopeia 9.0. Spectrophotometry was used to quantify biologically active substances. The antioxidant activity was determined by the potentiometric method. Potentiometric measurements were performed on a HANNA 2550 pH meter (Germany) with a combined platinum EZDO 50 PO electrode (Taiwan). A UV-1000 spectrophotometer (China) was used to measure the optical density. Results and discussion. The total content of phenolic compounds was 9.60 ± 0.17, 1.30 ± 0.03 and 0.12 ± 0.002 %, catechins – 9.20 ± 0.18, 1.20 ± 0.02 and 0.07 ± 0.002 %, flavonoids – 0.27 ± 0.005, 0.04 ± 0.001, 0.005 ± 0.001, hydroxycinnamic acids – 0.49 ± 0.01, 0.07 ± 0.002 and 0.007 ± 0.001 %, dry residue – 10.75 ± 0.11, 1.59 ± 0.02 and 0.15 ± 0.002 %, the antioxidant activity was 474.08 ± 9.48, 67.70 ± 1.35 and 7.01 ± 0.14 mmol-equiv mdry res(-1) for the first, second and third extraction, respectively. According to the results obtained, the optimal number of extractions of the raw material with 60 % ethanol was found to be two. Conclusions. The dynamic of extractions of biologically active substances of green tea leaves has been studied by triple extraction of the raw material to find the optimal extraction frequency; for the first time, a method for determining the extraction frequency based on the antioxidant activity of the extracts has been developed and proposed. It has been found that the optimal extraction rate is 2 times. The results obtained will be used in the further production of herbal medicines, dietary supplements, and cosmetic products with a green tea extract.