Laccase-catalyzed conversion of green tea catechins in the presence of gallic acid to epitheaflagallin and epitheaflagallin 3-O-gallate

Green tea extract containing catechin mixtures was treated with gallic acid using laccase (EC 1.10.3.2) to improve its function as a food material. After enzymatic oxidation, two new products were detected on an HPLC chromatogram. These products were purified by extraction with ethyl acetate, sequential column chromatographies, and crystallization. On the basis of 1H/13C NMR, MALDI-TOF/high resolution MS, and UV-visible absorption spectral analyses, they were confirmed to be epitheaflagallin (5) and epitheaflagallin 3-O-gallate (6). This enzymatic process allows us to preferentially convert catechin derivatives in a crude mixture of green tea into different compounds.

Epitheaflagallin (5) and epitheaflagallin 3-O-gallate (6), which are minor components of black tea, were preferentially synthesized from EGC (3) and EGCG (4) in green tea extracts using laccase and gallic acid. This biooxidation process could be applicable to the production of epitheaflagallin derivatives to improve the functionality of green tea.