Extraction and Purification of Bowl Tea Polyphenols

A 500 g raw Bowl tea (RBT) sample was crushed into powder, and 50 mL 45% (volume ratio) ethanol solution was added to the RBT powder and extracted at 90 °C for 30 min. After a repeated extraction, two extracts were combined, and the pH of the total extract was adjusted to 6.0. Then 800 mL mixed precipitant of AlCl₃ (30 g, Tianjin Damao Chemical Reagent Factory, Tianjin, China) and ZnCl₂ (60 g, Tianjin Damao Chemical Reagent Factory, Tianjin, China) was added to the extract for precipitation, and then the mixture was centrifuged at 3000× g for 10 min. 1000 mL hydrochloric acid (12%, volume ratio, Tianjin Damao Chemical Reagent Factory, Tianjin, China) was added to the collected precipitation for transsolution. The supernatant was separated, and 50 mL ethyl acetate (Tianjin Damao Chemical Reagent Factory, Tianjin, China) was added twice for extraction. Finally, the extract was subjected to rotary evaporation to obtain RBTP [15 (link)].