Fig. 13.

Structures of the metabolites in the metabolic pathway of β-apo-8′-carotenal in Caco-2 cells. There was rapid uptake of β-apo-8′-carotenal into cells, and β-apo-8′-carotenal was largely converted to β-apo-8′-carotenoic acid. Several studies show that this apocarotenoic acid is a major metabolite present in the serum and tissues of animals fed β-apo-8ʹ-carotenal (38, 39). This metabolic conversion is similar to what is observed with retinal, which can be converted to retinol or RA. β-Apo-8′-carotenal was also converted to a minor metabolite that was identified as 5,6-epoxy-β-apo-8′-carotenol, which is analogous to the formation of epoxy metabolites of vitamin A in vivo (41, 42).