LINOLEIC-ACID AND ALPHA-LINOLENIC ACID LIGHTENS ULTRAVIOLET-INDUCED HYPERPIGMENTATION OF THE SKIN

This study was conducted to evaluate the effects of unsaturated fatty acids on ultraviolet-induced hyperpigmentation of the skin. An efficie nt lightening effect was observed following topical application of lin oleic acid or a-linolenic acid to UV-stimulated hyperpigmented dorsal skin of brownish guinea pigs, The number of melanocytes in the treated skin was similar to the number in the skin of the pigmented control, indicating that the pigment-lightening effect was not due to depletion of melanocytes. In vitro experiments using cultured murine melanoma c ells showed that melanin production was inhibited most effectively by alpha-linolenic acid, followed by linoleic acid and then by oleic acid . Furthermore, the turnover of the stratum corneum, which plays an imp ortant role in the removal of melanin pigment from the epidermis, was accelerated by linoleic acid and by alpha-linolenic acid. Taken togeth er, the results suggest that the pigment-lightening effects of linolei c acid and a-linolenic acid are, at least in part, due to suppression of melanin production by active melanocytes, and to enhanced desquamat ion of melanin pigment from the epidermis.