What’s the function of green tea extract ?

What ‘s the function of green tea extract ?   Green tea is tea shoots buds , leaves, stems, after fixing, rolling , drying and other process made early tea ( or called Maocha ) and by shaping , classification process made of refined tea ( also known as the finished product tea ) ; is to keep the green features, for drinking tea. Is not fermented tea , its processing is characterized by high temperatures at the beginning of [...]