In Vitro Evaluation of Skin-Related Physicochemical Properties and Biological Activities of Astaxanthin Isomers.

Dietary astaxanthin exists predominantly as the all- E -isomer; however, certain amounts of the Z -isomers are universally present in the skin, whose roles remain largely unknown. The aim of this study was to investigate the effects of the astaxanthin E / Z -isomer ratio on skin-related physicochemical properties and biological activities using human dermal fibroblasts and B16 mouse melanoma cells. We revealed that astaxanthin enriched in Z -isomers (total Z -isomer ratio = 86.6%) exhibited greater UV-light-shielding ability and skin antiaging and skin-whitening activities, such as anti-elastase and anti-melanin formation activities, than the all- E -isomer-rich astaxanthin (total Z -isomer ratio = 3.3%). On the other hand, the all- E -isomer was superior to the Z -isomers in singlet oxygen scavenging/quenching activity, and the Z -isomers inhibited type I collagen release into the culture medium in a dose-dependent manner. Our findings help clarify the roles of astaxanthin Z -isomers in the skin and would help in the development of novel skin health-promoting food ingredients.