]. Cosmet. Sci., 58, 385-391 CTuly/August 2007) Hair melanin content and photodamage ANA CAROLINA SANTOS NOGUEIRA and INES JOEKES, Chemistry Institute, State University of Campinas-UNICAMP, CP 6154, 13084-971, Campinas, SP, Brazil. Synopsis The aim of this study was to compare the susceptibility of hair with different melanin content (virgin white, bl�nd and dark-brown) to photodegradation, evaluating changes on hair color and mechanical properties. Light exposure was carried out with a mercury-vapor lamp for up to 1800h. It was observed that color changes are different for each hair type and dependent on the wavelength range. Breaking elongation and breaking strength were affected in all hair types, mainly by UVB radiation. Results show that the melanin type and content of each hair is not the only parameter related to hair damages caused by sun exposure. INTRODUCTION The human hair fiber is composed mainly of keratins, a group of insoluble cystine- containing helicoidal protein complexes, which account for 65% to 95% of the hair by weight. The remaining constituents are water, lipids, pigments, and trace elements (1). The greatest mass pf the hair shaft is the cortex, which is responsible for the mechanical properties of the fiber. These properties are dependent on time, temperature and hu- midity (2). Inside the cortex are also located the melanin granules (about 3% by weight). These are the hair pigments, whose type, size and quantity establish hair color. There are two types of melanin, the brown-black pigment (eumelanin) and the less prevalent red pigment (pheomelanin). The chemical structures and molar masses of the melanins are not yet known (3), mainly because they are highly insoluble materials of presumably high molar mass and are therefore difficult to separate from the other cellular compo- nents of the structures in which they occur (4,5 ). Surrounding the cortex is the cuticle, a layer of overlapping, keratinized scales, which can account for 10% of the hair fiber by weight and has the role of protecting the fiber against environmental and chemical damage (6,7). As the cuticle protects the cortex, damage in the cortex generally occurs after extensive damage to hair cuticle. It is well known that solar radiation causes dryness, reduced strength, rough surface texture, loss of color, decreased luster, stiffness, brittleness and an overall dull, unheal appearance of the hair. These damages cause degradation of cystine, but the exact mechanism is not well known (8). Hair melanins provide some photochemical protection Address all correspondence to Ines Joekes. 385

386 JOURNAL OF COSMETIC SCIENCE to hair proteins, especially at lower wavelengths, where both the pigments and the proteins absorb light, by absorbing and filtering the impinging radiation and subse- quently dissipating this energy as heat. Their high absorption capacity can be explained in terms of their extensive system of conjugate carbonyl groups and double bonds. This not only captures a large fraction of the radiation but also immobilizes many of the free radicals formed upon the absorption of the UV radiation by the photo-sensitive amino acids in hair, preventing the transport of these free radicals into the keratin matrix. However, in the process of protecting the hair proteins from light, the pigments are degraded or bleached (9-11). Contradictions are still found in the literature about the effect of specific wavelength ranges of the solar radiation on hair properties and the sensibility of different hair types to photodegradation. Authors generally attribute hair damage to the total ultraviolet range of the solar spectrum and relate the photo-sensibility of light and dark hair to the hair melanin type. The aim of this work was to quantify and compare the effect of different UV wavelength ranges on the mechanical properties and color of hair with different melanin content. In this way, we hope to improve knowledge on the interac- tions of human hair with solar radiation. MATERIALS AND METHODS HAIR SAMPLES Tresses of (blended) virgin dark-brown and blond hair from De Meo Brothers Inc. (New York, USA) and virgin white hair from a volunteer were used. Each tress, weighing 2.0 g and approximately 20-cm in length, was washed two times with 2.0% w/w sodium lauryl sulfate aqueous solution, as follows: (a) hand-washing with 1 ml of the solution for 1 min (b) rinsing with 40°C water for 1 min (c) wet combing four times using a polypropylene comb. Afterwards, they were dried at room temperature, combed and stored. RADIATION EXPOSURE Sun exposure was simulated by irradiation with a mercury vapor lamp (OSRAM HQL 125W, Sao Paulo, Brazil). Full or UVB filtered radiation conditions were used as described in a previous work (12). The tresses were irradiated for 448 and 1792 h at 30 ± 2 °C and 50 ± 2 % RH. The values of radiation intensity obtained for the mercury- vapor lamp were 1.5 ± 0.5 W/m2 (UVB), 26.0 ± 1.0 W/m2 (UV A) and 70.0 ± 1.0 W/m2 (visible plus infrared radiations), summing a total radiation intensity of97.5 ± 1.0 W/m2. This value is around seven times smaller than that measured for the sun (692.0 ± 1.0 W/m2). Considering that lh sun exposure is "equivalent" to 7-h lamp exposure and 4 h of sun exposure per day, in this work we have simulated 16 and 64 sun exposure days. COLOR CHANGES Changes in the hair color were measured by diffuse reflectance spectrophotometry (DRS),