Effects of p-coumaric acid on erythema and pigmentation of human skin exposed to ultraviolet radiation

It has been recently recognized that p-coumaric acid (PCA) is a strong inhibitor of cellular melanogenesis.To evaluate the erythema-suppressive and skin-lightening effects of PCA after topical application to human skin.The control and PCA cream products were applied twice daily to the skin of the forearm of 21 subjects before and after ultraviolet (UV) irradiation to determine whether they could prevent erythema formation and pigmentation. The cream products were also applied to different areas only after the induction of erythema or pigmentation to determine whether they could have a depigmenting effect.A 7-day application of control and PCA cream products before UV irradiation decreased UV-induced erythema formation by 31% and 77%, respectively, compared with untreated skin. When the PCA cream was applied after UV irradiation, its effects on skin colour or pigmentation were less remarkable. However, the melanin index was significantly decreased at the sites treated with PCA cream for 70 days compared with control sites, and the Individual Typology Angle (ITA°) value was increased significantly. Of the 21 subjects, 2 had mild adverse skin reactions to both the PCA and control creams.These results suggest that PCA cream can reduce UV-induced erythema formation and subsequent pigmentation in human skin.