FIG 6.

Schematic representation of hydroxycinnamic acid metabolism in L. plantarum WCFS1. When R₁ is –OH and R₂ is –H, the represented compounds are p-coumaric acid (B), vinylphenol (C), ethylphenol (D), and phloretic acid (E). The esters (A) are methyl p-coumarate or ethyl coumarate when R₃ is –OCH₃ or –OCH₂CH₃, respectively. When R₁ is –OH and R₂ is –OH, the represented compounds are caffeic acid (B), vinylcatechol (C), ethylcatechol (D), and hydrocaffeic acid (E). The esters (A) are methyl caffeate or ethyl caffeate when R₃ is –OCH₃ or –OCH₂CH₃, respectively. When R₁ is –OH and R₂ is –OCH₃, the compounds are ferulic acid (B), vinylguaiacol (C), ethylguaiacol (D), and hydroferulic acid (E). The esters (A) are methyl ferulate or ethyl ferulate when R₃ is –OCH₃ or –OCH₂CH₃, respectively. When R₁ is –H and R₂ is –OH, only the reduction reaction is carried out, and the represented compounds are m-coumaric acid (B) and 3-(3-hydroxyphenyl) propionic acid (E).