Mechanism of oolongtheanin formation via three intermediates

To clarify the mechanism of oolongtheanin formation, the oxidations of (−)-epigallocatechin and (−)-epigallocatechin gallate were investigated, and key intermediates were isolated. These intermediates were determined to be dehydrotheasinensins and pro-oolongtheanins, which we have reported previously, and one novel intermediate. Based on the chemical structures of these intermediates, a mechanism was proposed for oolongtheanin formation from catechins, and confirmed by NMR and GC–MS analysis.