HAIR MELANIN 185 Table II Alterations in the Color of Light-Brown and Black Human Hair After 6 Weeks of Irradiation With Simulated Segments of the Sunlight Spectrum Color alteration Spectral range Light-brown Black UV-B Tips lighter Unaltered UV-A Somewhat lighter Unaltered Visible light Significantly lighter Somewhat lighter IR Unaltered Unaltered Global Lighter Somewhat lighter a,b Figure 1. Scanning electron micrographs of isolated melanin granula from untreated human hair. The bars correspond to length of 1 Ixm. a: Black hair granula. b: Light-brown hair granula. enzymatic removal of the keratin. After a 24-h hydrolysis of the melanin-CMC mixture, the yield of the remaining granules was determined to assess the effect of the irradiation spectrum on the melanin content (Figure 2). A subsequent long-term hydrolysis and delipidization led to a higher purity of the melanin sample for the IR investigations, but purity could not be determined quantitatively because of the small quantity of the available material and the inherent experimental error. The yield of melanin granules derived from untreated black hair was 4.8 % (+/- 0.25 %) and from untreated light-brown hair 3.95 % (+/- 0.3 %) of the total hair weight (Figure 2). While it has been found that the melanin granules of the black hair were only slightly affected by irradiation with visible and global light, the yields of the granules from the light-brown hair were significantly reduced by such irradiation and mostly by UV-A light (44 % less than the unirradiated sample). UV-B showed only limited effect, and the IR segment had no effect on the melanin yield. These results correlate with the results of the color measurements given in Table II. IR SPECTROSCOPY OF THE MELANIN FROM INTACT AND IRRADIATED HAIR It is assumed that the IR spectroscopic investigation of the melanin might provide some insight into changes occurring in the melanin polymers as the result of irradiation.

186 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS v• 4,5 • 4 e- 3,5 0'• 3 .c= 2,5 _.m 2 E 1,5 0 1 =__ 0,5 ß -• O. : : : : : I : : : : : : m '-- o m '-- o • • • -- _ • •) • -- _ light-brown hair black hair Figure 2. Melanin yields of intact and irradiated black and light-brown hair in relation to the different segments of the sunlight spectrum. The transmission spectrum (diamond cell) of the melanin samples led to a more satis- factory result than the KBr pellets (better band resolution). The IR transmission spectra of the melanin isolated from the black and light-brown hair are given in Figure 3. They conform well to the spectra of both synthetic (4) and natural melanin (12,17). --1 Spectral characteristics ofeumelani,. The broad absorptions between 3600 and 2500 cm 2 b[c]ck • • [ighf-brow i I i I i j 4000 3680 2960 2460 1920 1400 880 360 Wovenumber in crn -• Figure 3. FTIR spectra of intact black and light-brown hair. Assignment of bands of Table III.