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Photoprotection by dietary carotenoids has been linked to their antioxidant properties, in particular quenching of singlet molecular oxygen and scavenging of peroxyl radicals. Here, we compared the DNA-protection and antioxidant effects of selected carotenoids exclusively synthesized in red pepper (capsanthin and capsorubin) to the xanthophyll lutein. Preincubation of human dermal fibroblasts (hdf) with capsanthin and capsorubin significantly counteracted UVB induced cytotoxicity at doses between 0 and 300 mJ cm(-2). Pretreatment of hdf with capsanthin, capsorubin or lutein (1 μM) significantly decreased the formation of DNA strand breaks following irradiation with UVB light. All carotenoids studied decreased caspase-3 cleavage (a marker for UVB-induced apoptosis), however, caspase dependent PARP-1 cleavage was not affected suggesting that the remaining caspase activity is sufficient to promote UVB-induced apoptosis. It is conceivable that carotenoids selectively interfere with cellular responses activated by UVB-mediated damage. Our findings indicate that capsanthin and capsorubin exhibit similar properties to lutein and could be used as a dietary supplement to improve natural photoprotection.

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This study analyzed the assimilation efficiency of carotenoids when they are delivered as inclusion complexes with beta-cyclodextrin (CyDIC) in water. The in vitro assimilation model used was the brush border membrane vesicles (BBMV) system in which the BBMVs were incubated with CyDIC. Carotenoid suspensions in Tween were used as a reference. Regardless of the form in which the carotenoids were delivered to the BBMV preparation, a higher assimilation efficiency was observed for carotenes than for the xanthophyll lutein. At the highest donor solution concentration, supplying carotenoids in CyDIC produced a significant increase in carotenoid assimilation compared to the corresponding carotenoid suspensions in Tween. The assimilation process using CyDIC takes place by means of a dissociation process in which the carotenoids are released from the beta-cyclodextrin to later be assimilated. At the highest concentration of CyDIC in the donor solution, the dissociation equilibrium will be shifted toward the free forms of the complex, thus increasing the amount of carotenoids available for assimilation. In another set of experiments, the effect of high-density lipoproteins as activity inhibitors for the receptors involved in carotenoid assimilation was analyzed. In carotenoid suspensions in Tween, with an inhibitor, a significant decrease in the assimilated quantity compared was observed with values reached without the inhibitor. Lutein presented the most significant decrease (70%). The fact that complete inhibition was not reached suggests that both simple and facilitated diffusion contributes to the assimilation process. When the donor solution composed of CyDIC and inhibitor was added, significant increases were observed in beta-carotene and lycopene assimilation for all concentrations and in lutein for the highest concentration. This effect is due to the exchange between lipoprotein lipid components and CyDIC, which promotes the dissociation and liberation processes of the carotenoid, which then becomes available for assimilation.