Formation Of Epoxycarotenoids And Apocarotenals From Lycopene By Chemical Reactions And Autoxidation In Model Systems And In Processed Foods

A better understanding of the reactions and the underlying mechanisms of the oxidative degradation of carotenoids is needed not only in avoiding losses of these important compounds during processing and storage of foods, but also in evaluating the implications to in vivo biological processes. In this study, the products formed by epoxidation with m-chloroperbenzoic acid (MCPBA), oxidative cleavage with KMnO4, and autoxidation in low-moisture and aqueous model systems, in the presence and absence of light, at ambient condition were identified. The presence of oxidation products was also verified in processed products (tomato juice, tomato paste, tomato puree, guava juice, and "goiabada"). Lycopene-5,6,5',6'-diepoxide, lycopene-1,2,1',2'-diepoxide, 2,6-cyclolycopene-1, 5-diol, lycopene-1,2,5,6-diepoxide, lycopene-1,2,5',6'-diepoxide, lycopene-1,2-epoxide, lycopene-5,6-epoxide, and 2,6-cyclolycopene-1,5-epoxide were formed by the reaction of lycopene with MCPBA. The oxidation products produced with KMnO 4 were apo-15'-lycopenal, apo-14'-lycopenal, apo-12'-lycopenal, apo-10'-lycopenal, apo-8'-lycopenal, and apo-6'-lycopenal. Lycopene-5,6-epoxide, lycopene-5,6,5',6'-diepoxide, lycopene-1,2,1',2'- diepoxide, and apo-14'-lycopenal were not detected in the model systems and in the foods analyzed. However, the acid-catalyzed rearrangement product 2,6-cyclolycopene-1,5-diol and apo-12'-lycopenal were found in all model and food systems, and lycopene-1,2-epoxide and 2,6-cyclolycopene-1,5-epoxide were found in the model systems and in all but one ("goiabada") of the five foods analyzed. Lycopene-1,2,5',6'-diepoxide, apo-8'-lycopenal, and apo-6'-lycopenal were found in most of the systems, while apo-15-lycopenal and apo-10'-lycopenal were encountered in only a couple of systems. The inability to detect an intermediate product could be due to a fast turn-over. Increased Z-isomerization was also observed and Z-isomers of the oxidation products were detected.841367372Caris-Veyrat, C., Schmid, A., Carail, M., Böhm, V., Cleavage products of lycopene produced by in vitro oxidations: Characterization and mechanisms of formation (2003) J. Agric. Food Chem, 51, pp. 7318-7325Khachik, F., Steck, A., Niggli, U.A., Pfander, H., Partial synthesis and structural elucidation of the oxidative metabolites of lycopene identified in tomato paste, tomato juice, and human serum (1998) J. Agric. Food Chem, 46, pp. 4874-4884Rodriguez, E.B., Rodriguez-Amaya, D.B., Formation of apocarotenals and epoxycarotenoids from β-carotene by chemical reactions and by autoxidation in model systems and processed foods (2007) Food Chem, 101, pp. 563-57