Ultrasound-assisted extraction of bioactive compounds from green tea leaves and clarification with natural coagulants (chitosan and Moringa oleífera seeds).

In this study, a sequential process of extraction and clarification by natural coagulants and centrifugation successfully produced green tea extracts clear and enriched in bioactive compounds. Desirability function methodology was applied to optimize ultrasound-assisted extraction (UAE) of total polyphenols and flavonoids by the evaluation of the parameters temperature (22-83 °C), tea-to-water ratio (12-73 g  L-1) and amplitude (23-77%). Green tea clarification was carried out using the extract at UAE optimized conditions (77, 73 g L-1, 77%). The effect of centrifugation and the concentrations of chitosan (25-2000 mg L-1) and Moringa oleífera seeds (MOS) (100-10000 mg L-1) were evaluated. The best clarification conditions were at the concentrations of chitosan 500 mg L-1 and MOS 8000 mg L-1 followed by centrifugation. These optimized clarification conditions provided turbidity, solids and polyphenols reduction of 95% and 96%, 16 and 16%, 18 and 19% for chitosan and MOS treatments, respectively. The main individual compounds identified by high liquid chromatography (HPLC) were epigallocatechin gallate, epicatechin, epigallocatechin and catechin, gallic acid and caffeine.