j. Soc. Cosmet. Chem., 48, 133-140 (May/June 1997) A novel natural-based hair coloring process K. C. BROWN, E. MARLOWE, G. PROTA and G. WENKE, Research and Development Laboratories, Clairol Inc., 2 Blachley Road, Stamford, CT 06922 (K.C.B., E.M., G.W.), and Department of Organic and Biological Chemistry, University of Naples, Naples, Italy (G. P.) Accepted for publication July 31, 1997. Presented in part at the 5th World Congress of the International Society of Cosmetic Dermatology, Montecatini, Italy, October 26-29, 1995. Synopsis In an attempt to develop hair dye products that give more natural-looking colors, some of the basic steps from the natural biosynthetic pathway to melanin have been imitated chemically. Our hair coloring process starts with 3,4-dihydroxyphenylalanine (dopa). By careful selection of oxidant and oxidation conditions, dopa is converted on hair to 5,6-dihydroxyindole in high yield. This indole has been known for many years to be the immediate precursor to the black eumelanins, and it can be readily polymerized in situ to dye the hair an intense black color. Additionally, the natural process produces the red and yellow pheomelanins by incorporating sulfur-containing nucleophiles such as cysteine into the melanogenic process. We have also found that significant color changes can be produced by adding a variety of nucleophiles to the system, including cysteine and other thiols. By these means, a wide range of shades can be produced on hair under conditions acceptable to the user of the hair dye. Performance of the dyed hair appears to be comparable to that of current permanent dyes and is clearly superior in both application technique and performance to the alternative natural dye products available today. INTRODUCTION Until this century, alteration of the coloration of hair and skin for cosmetic purposes could only be achieved by the use of various types of naturally available materials. Frequently the color change required long processing times and stringent conditions, especially when lightening was desired, and the results were variable and usually not predictable. The discovery of synthetic dyes simplified the processing steps necessary for dyeing hair and gave much more reliable and versatile results, so that today, natural dye products account for an infinitesmally small fraction of hair dye sales. Even so, there is a growing trend towards the use of natural materials, despite the fact that most of the available natural dye products still rely on centuries-old technology along with its problems and inconveniences. The products are supplied as powders that require soaking in hot water to extract the active dye components. Since the dye content is generally low, 133

134 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS large volumes of powder are needed to obtain adequate color coverage on a whole head of hair. Also, because the product is applied to hair as a thick paste and the dyeing times range from one to two hours, the paste usually dries on the head during this time and becomes quite difficult to rinse out after dyeing. Probably the most serious deficiency, though, is the very limited range of colors available. These types of colors usually exclude the products from use for gray coverage, which is one of the major reasons that con- sumers turn to hair color products. While there are clearly a number of opportunities for product improvements in this area, we have chosen to take a different approach in our development of natural dye products. This paper is an account of our progress. MELANINS AND MELANOGENESIS Human hair and skin are colored by the presence of melanins, materials that are also responsible for coloration in many other animals and some plants. Many of the biological processes that form melanins are now adequately understood, and much research has been carried out in recent years on the structure and properties of the various melanins (1). Two different melanins are found in human hair: blonde, brown, and black hair contains eumelanin, while pheomelanin is found in red hair. It is believed that the melanins share a common biosynthetic pathway (1) with the selection controlled by the presence or absence in the melanocyte of thioIs such as cysteine. Eumelanins are polymers of 5,6- dihydroxyindole and its 2-carboxylic acid, both of which result from the enzymatically controlled oxidation and subsequent cyclization of dopa. In pheomelanocytes, however, dopaquinone, the oxidation product of dopa, reacts with cysteine to produce a mixture of cysteinyldopas that subsequently cyclize to benzothiazines, the building blocks of pheomelanin. A simplified reaction scheme is shown in Figure 1. The color of hair is thought to be largely produced by light scattering from the melanin CYS •OH OH $ENZOTHIAZIN•. ALANINE •i PHEOMELANIN8 EUMELANIN$ HO COOH H DHICA Figure 1. Simplified scheme for melanogenesis.