Dehydrometabolites of siphonaxanthin predominate in skin tissues and retain biological activity in keratinocytes.

Siphonaxanthin attenuated ultraviolet B (UVB)-induced cytokine expression in HaCaT cells and primary normal human epidermal keratinocytes. After oral intake of siphonaxanthin in mice, siphonaxanthin and its dehydrometabolites were detected in plasma and skin-related tissues, with dehydrometabolites predominating. The metabolites modulated UVB-induced responses as well as siphonaxanthin itself, suggesting that the metabolic conversion does not abolish the activity.