Extraction of spent green tea leaves as bioactive-compound source

Spent green tea leaves (SGTL) are a major contributor to the high cost of commercial tea products because of the large amount of leftover and the cost of disposal. This research investigates on the solvent and time for the extraction of SGTL that provides good yield of potential compound and to separate bioactive compounds as enrich-fractions and pure compounds. The obtained fractions were evaluated for antioxidant, antityrosinase, anticholinesterase and plant growth regulator activities. Caffeine was found in all samples. Among five extracts, the dichloromethane extract revealed high caffeine content (92.8 %peak area), while the methanol extract showed the highest five-catechin content (64.5 %peak area). Further separation of the latter by liquid-liquid extraction, the aqueous phase was extracted with ethyl acetate to gain high catechin family content (EGC, C, EC, EGCG, ECG) fraction with low caffeine. Four subfractions were separated from enrich-catechin family fraction. The enrich-caffeine and enrich-catechin family fractions displayed remarkable biological effects. Caffeine, gallic acid and ECG were bioactive compounds responsible for the biological activity in SGTL. Bioactive compound were isolated from SGTL showed bilogical activity including antioxidant, antityrosinase, anticholinesterase and plant growth regulation. SGTL was proved to be an excellent source of bioactive compounds. The enrich fractions served as prospective materials for the exploration of new multi-functional food and drug formulations.