5,5'-dicapsaicin, 4'-O-5-dicapsaicin ether, and dehydrogenation polymers with high molecular weights are the main products of the oxidation of capsaicin by peroxidase from hot pepper

The nature of the products of capsaicin oxidation by hot pepper peroxidase was studied by gel permeation chromatography. Three main types of oxidation products were identified. Peak 1, with an average molecular weight of 603 +/- 12 and corresponding to dimers of capsaicin, was resolved by gas chromatography-mass spectrometry into the dimers 5,5'-dicapsaicin (1a) and 4'-O-5-dicapsaicin ether (1b). Peak 2 appears to be a polymeric product with a molecular weight of 4500 and probably corresponds to polymeric products with a mean degree of 15. Capsaicin-protein copolymers (peak 3) also appear to be products of capsaicin oxidation, probably arising from protein and capsaicin copolymerization. These results suggest that Capsicum peroxidase oxidizes capsaicin to yield 5,5'-dicapsaicin and 4'-O-5-dicapsaicin ether, together a mixture of highly polymerized dehydrogenation products, all of them therefore of a lignin-like nature.