Phytoene and Phytofluene Isolated from a Tomato Extract are Readily Incorporated in Mixed Micelles and Absorbed by Caco-2 Cells, as Compared to Lycopene, and SR-BI is Involved in their Cellular Uptake.

SCOPE: Absorption mechanisms of phytoene (PT) and phytofluene (PTF) are poorly known. The main objectives of the study are to measure their micellization and intestinal cell uptake efficiencies and to compare them to those of commonly consumed carotenoids. Other objectives are to assess the involvement of protein(s) in their cellular uptake and whether they compete with other carotenoids for micellization and cellular uptake.

METHODS AND RESULTS: Tomato-extract-purified PT and PTF, mainly present as cis-isomers, are much better incorporated in synthetic mixed micelles than pure all-trans lycopene. PT impairs lycopene micellization (-56%, P < 0.05) while PT and PTF do not significantly affect the micellization of other carotenoids, and vice versa. At low concentration, Caco-2 PTF uptake is higher (P < 0.05) than that of PT and lycopene (29%, 21%, and not detectable). SR-BI, but not CD36 neither NPC1L1, is involved in PT and PTF uptake. PT and PTF impair (p < 0.05) β-carotene uptake (-13 and -22%, respectively).

CONCLUSIONS: The high bioaccessibility of PT and PTF can be partly explained by their high micellization efficiency, which is likely due to their natural cis isomerization and/or to their high molecular flexibility. SR-BI is involved in their cellular uptake, which can explain competitions with other carotenoids.