PHOTOCHEMICAL ALTERATIONS IN HUMAN HAIR .2. ANALYSIS OF MELANIN

A brief investigation was carried out of changes in the melanin pigmen t that occur during the irradiation of hair with simulated UV-B, UV-A, visible light, infrared light, and total sunlight. After six weeks of irradiation, the pigments were isolated from hair samples and the cha nges in their physicocharacteristics were evaluated. The melanin appea rs to be affected most by visible light, although the pigment of black and dark brown hair (predominantly eumelanin) is less changed than th at of light-brown hair (a mixture of eu- and pheomelanins). The weight losses of melanin correlate with photochemically induced alterations of the melanin polymer. IR spectroscopic investigations characterize t he eumelanin by five peaks and the pheomelanin by six peaks in the ran ge of 1800 to 500 cm(-1). The intensity of some of these peaks decreas es, depending on the irradiation wavelength and on the origin of melan in pigments.