PHOTOCHEMICAL ALTERATIONS IN HUMAN HAIR 207 o 1 '•• Light-unfrbrow ½ 'l J Jl , , Light-brown, irradiated ,, "• ',,' I i J• • TLC- development Figure 4. Influence of six-week global radiation on the lipid fractions from blond human hair. Qualitative and quantitative determination occurs by comparison of densitograms from IL extracts separated by thin- layer chromatography. DISCUSSION IL from blond and black hair contain the same lipid fractions in comparable amounts. Irradiation with sunlight degrades the IL from blond hair more than those from black hair. UV-B and UV-A destroy in blond hair approximately 25% of the cholesterol. VIS and global radiation even degrade 60% and more of the initial cholesterol content. In contrast, the cholesterol fraction from black hair is not significantly altered by UV-B, UV-A, and visible light in contrast with blond hair, global radiation leads only to a lower extent (24%) of photooxidation of cholesterol in black hair. The photochemical degradation of FFA occurs in blond and black hair by the influence of UV-B and UV-A to comparable degrees. UV-B irradiation reduces the FFA amount by approximately 40% and UV-A irradiation by approximately 20%. Differences as a function of the type of pigmentation can be detected for hair irradiated with VIS. The FFA fraction from blond hair is photooxidized by this radiation range by more than 50% and that from black hair by only 23%. With the exception of the FFA fraction from black hair, IR irradiation does not show a significant degradation of lipids. Global irradiation causes in blond hair a degradation of fatty acids of 33% and in black hair of 42%. The lower photooxidative degradation in black hair suggests that eumelanin, the pig- ment in black hair, is responsible for this effect. It protects the IL mainly from the photochemical influence of the visible range of sunlight. The protective function of melanin against photodegradation also applies to the UV-B and UV-A ranges. The effects of a partial (UV) or very drastic (VIS) destruction of IL in hairs not suffi-

208 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS t- TL[- development Figure 5. Influence of six-week global radiation on the lipid fractions from black human hair. Qualitative and quantitative determination occurs by comparison of densitograms from IL extracts separated by thin- layer chromatography. 700 .•. .c 600 o 500 = 400 'B 300 *• 200 o 100 light-brown black Figure 6. Influence of specific ranges of sunlight (UV-B, UV-A, VIS, IR, global) on quantitative changes in the cholesterol fraction from blond and black human hair (irradiation for approximately 1000 h).