Bulk preparation of (−)-epigallocatechin gallate-rich extract from green tea

• A three-stage process was developed for bulk preparation of EGCg-rich extract.
• Either of crude tea extract or green tea leaf is viable as raw material.
• High EGCg >700 mg g−1 and low caffeine <1 mg g−1 products are obtained.
• Solvent extraction and silica column purification are the major procedures.
• No toxic solvents or metal ions are used.

(−)-Epigallocatechin gallate (EGCg)-rich extract (EGCg > 700 mg g−1) was prepared from green tea leaves through a three-stage process consisting of liquid–liquid extraction and silica column purification. Crude tea extract was dissolved in ethyl acetate. After filtration, the solution was extracted by 10 g L−1 citric acid solution twice, and then passed through silica column. The catechins compounds in the ethyl acetate eluate were back extracted to the aqueous phase, then extracted with a mixed solution of n-hexane/ethyl acetate (2/5, v/v) 3 times, concentrated, and freeze dried. 12.8 g EGCg-rich extract containing 709 mg g−1 EGCg and 965 mg g−1 total catechins was obtained from 300 g green tea leaves, with an EGCg recovery of 26.1% and a yield of 4.3%. This method was suitable for bulk preparation of EGCg-rich catechins from green tea leaves.