Enzymatic and oxidative metabolites of lycopene

Using the post-mitochondrial fraction of rat intestinal mucosa, we have investigated lycopene metabolism. The incubation media was composed of NAD+, KCl, and DTT with or without added lipoxygenase. The addition of lipoxygenase into the incubation significantly increased the production of lycopene metabolites. The enzymatic incubation products of 2H10 lycopene were separated using high-performance liquid chromatography and analyzed by UV/Vis spectrophotometer and atmospheric pressure chemical ionization–mass spectroscopy. We have identified two types of products: cleavage products and oxidation products. The cleavage products are likely: (1) 3-keto-apo-13-lycopenone (C18H24O2 or 6,10,14-trimethyl-12-one-3,5,7,9,13-pentadecapentaen-2-one) with λmax = 365 nm and m/z = 272 and (2) 3,4-dehydro-5,6-dihydro-15,15′-apo-lycopenal (C20H28O or 3,7,11,15-tetramethyl-2,4,6,8,12,14-hexadecahexaen-1-al) with λmax = 380 nm and m/z = 284. The oxidative metabolites are likely: (3) 2-apo-5,8-lycopenal-furanoxide (C37H50O) with λmax = 415 nm, 435 nm, and 470 nm, and m/z = 510; (4) lycopene-5, 6, 5′, 6′-diepoxide (C40H56O2) with λmax = 415 nm, 440 nm, and 470 nm, and m/z = 568; (5) lycopene-5,8-furanoxide isomer (I) (C40H56O) with λmax = 410 nm, 440nm, and 470 nm, and m/z = 552; (6) lycopene-5,8-epoxide isomer (II) (C40H56O) with λmax = 410, 440, 470 nm, and m/z = 552; and (7) 3-keto-lycopene-5′,8′-furanoxide (C40H54O2) with λmax = 400 nm, 420 nm, and 450 nm, and m/z = 566. These results demonstrate that both central and excentric cleavage of lycopene occurs in the rat intestinal mucosa in the presence of soy lipoxygenase.