Changes in Grape Seed Phenols as Affected By Enzymic and Chemical Oxidation in vitro

ABSTRACT An in vitro oxidation system containing all the phenolic compounds of an extract of grape seeds and phenol oxidases (catechol oxidase from grapes and laccase from grey mold of grape Botrytis cinerea) was used to determine the effects of enzymic oxidation on seven phenolic compounds: gallic acid, (+)‐catechin; (‐)‐epicatechin and four procyanidins, dimers of (+)‐catechin and (‐)‐epicatechin units. HPLC determinations showed that there was considerable depletion of phenolic compounds in the extract by both enzymes since the quantities of all the compounds fell during enzymic oxidation. When a pure chemical oxidation was compared, the decrease was very much slower.