Orange peel extract, containing high levels of polymethoxyflavonoid, suppressed UVB ‐induced COX ‐2 expression and PGE 2 production in HaCaT cells through PPAR ‐ γ activation

Ultraviolet light ( UV ) induces an inflammatory response in the skin by cyclooxygenase ( COX )‐2 expression and prostaglandin ( PG ) E 2 production. Citrus peel has been used as a natural medicine. It contains polymethoxyflavonoids ( PMF s) as a major ingredient, which have anti‐inflammatory activity. We obtained orange peel extract containing high levels of PMF s. The extract suppressed UVB ‐induced COX ‐2 expression and PGE 2 production in HaCaT cells . Furthermore, it was found that this extract acted as a peroxisome proliferator‐activated receptor ( PPAR )‐ γ agonist. The suppression of UVB ‐induced COX ‐2 expression by this extract was inhibited by GW 9662 and T0070907, which are both PPAR ‐ γ antagonists. It is therefore suggested that orange peel extract, containing high levels of PMF s, suppresses UVB ‐induced COX ‐2 expression and PGE 2 production through PPAR ‐ γ . Hence, these extracts could provide useful protection against or alleviation of UV damage.