a step-wise consideration of these cyclizations shows the first as leading to a catecholic structure considerable as precursor to both ellagic acid and chebulic acid. while ellagic acid would simply be formed from this precursor by further cyclization, chebulic acid could be considered as formed from it via selective cleavage of its catechol ring by an intradiol catechol dioxygenase followed by the reduction of the generated muconate analogue intermediate by an FADH2-dependent oxidoreductase.