Apo-8′-lycopenal and Apo-12′-lycopenal are metabolic products of lycopene in rat liver

The health benefits of lycopene as an anticarcinogenic compound have been widely studied but little is known about the metabolic products of lycopene produced in vivo. We investigated lycopene metabolites in the liver of F344 male rats that had been prefed a lycopene-containing diet (0.25 g lycopene/kg diet). After 30 d of feeding, they were given a single oral dose of ¹⁴C-labeled lycopene (421.8 kBq). The metabolic products of both nonradioactive and ¹⁴C-labeled lycopene in rat liver were extracted and separated using HPLC and analyzed by UV/VIS spectrometry, online radioactive detection, and off-line and in-line positive ion electrospray ionization MS. Among a number of metabolite products formed, we identified apo-8′- lycopenal (λ_max = 473 nm and m/z = 417). The putative compound, apo-12′-lycopenal, was detected but no apo-10′-lycopenal was present. A number of other very polar, short-chain and/or short chromophore compounds with UV/VIS absorption <300 nm were present but were not characterized. These data show that lycopene is cleaved in vivo by rats at different positions to produce apo-12′-lycopenal, and other unidentified metabolites in addition to apo-8′-lycopenal. Apo-8′-lycopenal and the putative apo-12′-lycopenal are identified as lycopene metabolites in rat liver in vivo.