Pathway of Gallic Acid Biosynthesis and Its Esterification with Catechins in Young Tea Shoots

Abstract

Shikimic acid-G-¹⁴C, phenylalanine-U-¹⁴C, and trans-cinnamic acid-3-¹⁴C were incorporated into the gallic acid moiety of (—)-epicatechin-3-gallate and (—)-epigallocatechin-3-gallate in young tea shoots. The incorporation of shikimic acid-7-¹⁴C into the gallic acid was almost equal to that of shikimic acid-G-¹⁴C, i.e. decarboxylation of the side chain did not occur during the conversion of shikimic acid to gallic acid and the conversion apparently was due to dehydrogenation of the shikimic acid. These results suggest at least two pathways for gallic acid biosynthesis in tea shoots; a) a pathway through phenylpropanoid, and b) a pathway through the dehydrogenation of shikimic acid.

Esterification of gallic acid with catechins was also confirmed by tracer experiments in young tea shoots.