Fig. 14.

Structures of the metabolites in the metabolic pathway of β-apo-10′-carotenal in Caco-2 cells. There was rapid uptake of β-apo-10′-carotenal into cells, and β-apo-10′-carotenal was converted to a major metabolite that we identified as 5,6-epoxy-β-apo-10′-carotenol and a minor metabolite that is likely a dihydro-β-apo-10′-carotenol. Previous studies have suggested that β-apo-10′-carotenol, β-apo-10′-carotenoic acid, and β-apo-12′-carotenoic acid are detected in serum and tissues of animals given β-apo-10′-carotenal as the only source of provitamin A activity (39). However, in the present study, we did not detect any of these metabolites.