5-5´dicapsiate:Product of the oxidation of capsiate by cationic peroxidases from pepper (Capsicum annum L.).

Abstract

Capsiate, dihydrocapsiate, and nordihydrocapsiate are part of a group of metabolites from Capsicum annuum which are known as capsinoids. They are structurally and functionally similar to capsaicinoids, the substances that causes pungency in hot peppers, but the capsinoids are non-pungent compounds. The only structural difference between the capsaicinoids and capsinoids is the way in which the carbon chain is bound to the aromatic ring: by an amide moiety in capsaicinoids and by an ester moiety in capsinoids. Secretory plant peroxidases may be directly related to capsaicinoid metabolism, and the oxidation of capsaicin and dihydrocapsaicin by a pepper peroxidase was reported earlier. The aim of the present work was to study the ability of pepper peroxidases to oxidize capsiate. In order to obtain an extract enriched in basic peroxidases, a crude extract from local peppers was subjected to a two-step chromatography protocol. This extract oxidized capsiate following a Michaelis-Menten kinetic. The use of specific inhibitors confirmed the main role of secretory peroxidases in this oxidation. The MS spectrum (Orbitrap) of the principal oxidation-products, revealed a molecular ion of m/z=609, according to a 5-5’ dicapsiate structure. This compound is analogous to the main product previously described for the oxidation of capsaicin