Green tea leaves contain beneficial antioxidants which their major portion is converted to thearubigins and teaflavins (tea coloring constituents) during black tea processing and production. Because of the beneficial properties of these compounds and their applications in food, drug, health and cosmetics products, there has been a great deal of researches on the optimized extraction methods of these antioxidants.
In this research, the total amount of catechins in Iranian green tea leaves were measured in spring, summer, and fall seasons. Moreover, the catechins content of green tea leaves were measured at different extraction times and temperatures using solvents such as acetone, ethanol, acetonitrile, and water. The results indicated that the 50 percent solution of aqueous acetonitrile at its boiling point extracts the maximum amount of catechins. Finally, ultrasonic waves were used for extraction and purification of epigallocatechin gallate. According to these experiments, the optimum EGCG extraction conditions are 60oC, 40 min, and 540 watts of ultrasonic power.