These products help people get a jump-start on their summer glow without exposure to harmful ultraviolet radiation.
Aruba in a Tuba is just one of a hundred or more brands of creams, gels, mousses, and sprays that you can find at drug- stores, department stores, and salons. They all work the same way–that is, they all have the same active ingredient: dihydroxyacetone (DHA).
DHA is a simple sugar and is nontoxic. In fact, it is an intermediate in carbohydrate metabolism in higher plants and animals and is more rapidly metabolized than glucose in the body. Specifically, this three-carbon keto sugar is a physiologic product of the body formed and utilized during glycolysis–that quintessential metabolic process that we’ve all had to memorize at least once. DHA used in self-tanners is usually prepared by fermentation of glycerine by Acetobacter suboxydans.
Here is how it happens in self-tanners: The reaction of skin with DHA to produce an artificial tan proceeds through combination with free amino groups in skin proteins, and particularly by combination of DHA with the free guanido group in arginine. (Epidermal proteins have a very high content of the amino acids arginine, lysine, and histidine.) In related experiments, Wittgenstein found that arginine was the most reactive, with the appearance of a dark brown color within 30 minutes. Aqueous mixtures of DHA with glycine, lysine, and histidine also gave brown to yellow pigments. These pigments are called melanoidins. Melanoidins are polymeric compounds that are linked by lysine side chains to the proteins of the stratum corneum–which is the outermost, dead layer of human skin.
Visit “What’s That Stuff” to read more about self-tanners.
Excerpted with permission, Chemical & Engineering News
Copyright © 2000 American Chemical Society