Inhibitory effect of hydroxysafflor yellow a on mouse skin photoaging induced by ultraviolet irradiation.

Chronic exposure to ultraviolet (UV) irradiation is believed to be the major cause of skin damage that results in premature aging of the skin, so called photoaging, characterized by increases in skin thickness, formation of wrinkles, and loss of skin elasticity. UV induces damage to skin mainly by oxidative stress and collagen degradation. In this study, we examined the photo-protective effect of hydroxysafflor yellow A (HSYA), a major active chemical component isolated from Carthamus tinctorius L., by topical application on the skin of mice. Exposure of the dorsal depilated skin of mice to UV radiation four times a week for 10 weeks induced epidermal hyperplasia, elastin accumulation, collagen degradation, etc. HSYA at the doses of 50, 100, and 200 μg/mouse was topically applied immediately following each UV exposure. The effects of HSYA were evaluated by a series of tests, including macroscopic and histopathological evaluation of skin, pinch test, and redox homeostasis of skin homogenates. Results showed that the UV-induced skin damage was significantly improved after HSYA treatment, especially at doses of 100 and 200 μg/mouse. This protective effect is possibly related to the anti-oxidative property of HSYA and mediated by promoting endogenous collagen synthesis. This is the first study providing preclinical evidence for the protective effect of HSYA against photoaging.