Reversed-phase and size-exclusion chromatography as useful tools in the resolution of peroxidase-mediated (+)-catechin oxidation products

The peroxidase-catalysed oxidation of plant phenolics involves one-electron oxidation reactions, and yields unstable mono-radical species, which couple to generate heterogeneous product mixtures of different degrees of polymerisation. One such phenolic susceptible to oxidation by peroxidase is (+)-catechin. Low-pressure chromatography on Sephadex LH-20, using methanol as mobile phase, resolves the main peroxidase-mediated (+)-catechin oxidation products into a dimeric compound (dehydrodicatechin A) and an oligomeric fraction with a polymerisation degree equal or greater than 5. These pure fractions were used to develop rapid high-performance liquid chromatographic methods, both reversed-phase and size-exclusion chromatography for the direct analysis of the peroxidase-mediated (+)-catechin oxidation products. The joint use of both chromatographic systems permitted the qualitative and quantitative identification of the peroxidase-mediated (+)-catechin oxidation products, and can thus be considered as a useful tool for analysing the complex mixtures of natural bioactive plant products synthesized in reactions catalyzed by plant peroxidases.