Abstract
Endothelin-1 (ET-1), a powerful vasoconstrictor and mitogen for melanocytes, might be responsible for pigmentation that occurs after ultraviolet (UVB) -irradiation. We have previously reported that Sechium edule (S. edule) extract reduces ET-1 secretion in cultured human keratinocytes following UVB irradiation. In this study, we investigated the effect of S. edule extract on melanin synthesis and analyzed the polyphenols contained in the extract. A three-dimensional human skin model comprising normal epidermal keratinocytes and melanocytes was subjected to macroscopical pigmentation and quantitative analysis. The S. edule extract showed an inhibitory effect on macroscopic and microscopic darkening and melanin content; however it did not show an inhibitory effect on tyrosinase enzyme activity. High-performance liquid chromatography with coulometric array detection was employed to determine the polyphenols contained in the extract. The luteolin, ferulic acid, p-coumaric acid, vanillic acid, protocatechuic acid and p-hydroxybenzoic acid were found to be 6.6μg/g, 5.6μg/g, 3.3μg/g, 6.1μg/g, 1.5μg/g and 0.8μg/g (dry weight), respectively. This polyphenolic complex might result in the inhibitory effect of melanin synthesis.
