The protective effects of the topical application of orange peel cold-pressed oil (CPO), a rich polymethoxyflavones (PMFs) source, on ultraviolet B (UVB)-induced skin injury were studied. Depilated KM mice were irradiated by UVB at one minimal erythemal dose every day and the treated groups were smeared with CPO before radiation. After two weeks we found that CPO helped to maintain the dermal structure and enhanced serum levels and skin tissue expression of superoxide dismutase, catalase and glutathione peroxidase. In serum CPO lowered interleukin-6/-1 beta and tumor necrosis factor alpha levels; in skin it decreased the levels of type III collagen and H2O2 but increased hydroxyproline and type I collagen. Moreover, the skin expression of matrix metalloproteinases 2/9 was downregulated, whereas the expression of tissue inhibitor of metalloproteinases 1/2 was upregulated. The above effects followed a dose-dependent manner. Liquid chromatography analysis of irradiated skin tissue showed partial decomposition of PMFs into 5-hydroxy-PMFs.

Orange peel cold-pressed oil; Ultraviolet B; Methoxyflavones; Oxidative stress; Skin photoaging

Citrus Research Institute of Chinese Academy of Agricultural Sciences