Nguyen B-C, Kochevar I E
Wellman Laboratories of Photomedicine, Department of Dermatology, Massachusetts General Hospital, WEL-224, Harvard Medical School, 50 Blossom Street, Boston, MA 02114, USA.
Br J Dermatol. 2003 Aug;149(2):332-40. doi: 10.1046/j.1365-2133.2003.05434.x.
Sunless tanning preparations have been used for more than 50 years and are still very popular because they provide temporary pigmentation resembling an ultraviolet-induced tan. The pigment is the product of reactions between dihydroxyacetone (DHA) and amino acids in the stratum corneum.
To understand the factors that influence the reactions of DHA with amino acids in the stratum corneum with the ultimate goal of producing pigmentation with greater photoprotection.
The influence of hydration and/or oxygen on the development of DHA-induced pigment was assessed in vivo using an occlusive dressing and ex vitro on human epidermal preparations. Two spectroscopic techniques, diffuse reflectance and fluorescence emission, were used to monitor the extent of pigment development. The optimal relative humidity for DHA-induced pigmentation was assessed on the epidermal preparations. The formation of products from reactions between DHA and nine amino acids was studied in solutions buffered at pH 5 and 7.
Development of DHA-induced pigmentation was inhibited by a 24-h occlusive dressing but appeared after its removal, indicating that DHA was still present. High hydration but not the absence of oxygen inhibited coloration of occluded skin. The extent of pigmentation did not vary in a simple manner with hydration, as pigment formation was positively correlated with humidity from 0 to 75% but negatively correlated from 75 to 100%. Lysine, glycine and histidine reacted most rapidly with DHA, with reaction rates greater at pH 7 than at pH 5. The products absorbed with maxima at wavelengths up to 340 nm.
These results indicate that extent of hydration, pH and availability of certain amino acids influence the development of DHA-induced pigmentation in the stratum corneum and suggest that manipulation of these factors might produce pigmentation with greater photoprotection.
免晒美黑制剂已使用超过50年，且仍非常受欢迎，因为它们能提供类似紫外线诱导晒黑的临时色素沉着。该色素是二羟基丙酮（DHA）与角质层中氨基酸反应的产物。
了解影响DHA与角质层中氨基酸反应的因素，最终目标是产生具有更强光保护作用的色素沉着。
使用封闭敷料在体内评估水合作用和/或氧气对DHA诱导色素形成的影响，并在人体表皮制剂上进行体外评估。采用漫反射和荧光发射两种光谱技术监测色素形成的程度。在表皮制剂上评估DHA诱导色素沉着的最佳相对湿度。研究了在pH值为5和7的缓冲溶液中DHA与九种氨基酸反应产物的形成。
24小时的封闭敷料抑制了DHA诱导的色素沉着形成，但去除敷料后色素沉着出现，表明DHA仍然存在。高水合作用而非无氧状态抑制了封闭皮肤的着色。色素沉着程度与水合作用并非简单相关，因为色素形成在0至75%湿度时与湿度呈正相关，而在75至100%时呈负相关。赖氨酸、甘氨酸和组氨酸与DHA反应最快，在pH 7时的反应速率高于pH 5。产物在波长高达340 nm处有最大吸收峰。
这些结果表明，水合程度、pH值和某些氨基酸的可用性会影响角质层中DHA诱导的色素沉着形成，并表明对这些因素的调控可能产生具有更强光保护作用的色素沉着。
