Geometrical isomers of lutein and fucoxanthin: Unveiling their antioxidant potentials and skin-related biological activities

Although carotenoids are most commonly found in dietary sources as all-E-isomers, some carotenoids accumulate in the skin as Z-isomers; their roles are largely unknown. This study investigated the effects of E/Z-isomers of lutein and fucoxanthin, two xanthophyll carotenoids, on their antioxidant potential and skin-related biological activities. Evaluation of ultraviolet (UV)-blocking abilities demonstrated the superior performance of Z-isomer-rich lutein and fucoxanthin against UV-A and UV-B radiation, with Z-isomer-rich lutein exhibiting higher UV-B protection. Antioxidant assays revealed that all-E- and Z-isomer-rich lutein and fucoxanthin had potent singlet oxygen and hydroxyl radical scavenging activities. Moreover, Z-isomer-rich lutein and fucoxanthin exhibited enhanced lipid peroxidation scavenging compared with their all-E counterparts. Both isomers of lutein and fucoxanthin exhibited potent skin-antiaging and skin-whitening effects in several in vitro assays, including anti-elastase and anti-tyrosinase activities. These findings suggest that geometric isomers may enhance the therapeutic efficacy of carotenoids in skin care applications.