Age-dependent changes in eumelanin composition in hairs of various ethnic origins

• Published in: International journal of cosmetic science Vol. 34; no. 1; pp. 102 - 107
• Main Authors: Commo, S., Wakamatsu, K., Lozano, I., Panhard, S., Loussouarn, G., Bernard, B.A., Ito, S.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.02.2012; Wiley
• Subjects: Adolescent; Adult; African Americans; ageing; Asian Continental Ancestry Group; Biological and medical sciences; Child; dopachrome tautomerase; ethnic origin; eumelanin; European Continental Ancestry Group; Female; Fundamental and applied biological sciences. Psychology; Hair - chemistry; Hair Color; hair melanin; Humans; Male; Melanins - analysis; Middle Aged; Pyrroles - analysis; Statistics, Nonparametric; Vertebrates: skin, associated glands, phaneres, light organs, various exocrine glands (salt gland, uropygial gland...), adipose tissue, connective tissue; Young Adult; Human; ethnic origin; Asiatic; Dopachrome Δ-isomerase; Intramolecular oxidoreductases; Enzyme; Pigmentation; Ethnic group; Hair (head); dopachrome tautomerase; Isomerases; Pigments; hair melanin; Caucasoid; Age; Melanin; African American; eumelanin
• ISSN: 0142-5463; 1468-2494
• DOI: 10.1111/j.1468-2494.2011.00691.x

Synopsis Hair pigmentation is one of the most conspicuous phenotypes of humans. From a chemical point of view, however, data remain scarce regarding human hair pigmentation characteristics. To determine melanin content and composition in human eumelanic hair from individuals of different ethnic origins and at different ages, we collected hair from 56 subjects with eumelanic hair from each group of African‐American, East Asian, and Caucasian origin. The 56 subjects consist of 14, seven each of males and females, each from four age classes of younger than 11, between 12 and 19, between 20 and 45, and older than 46. We analysed hair colour scale, total melanin value, and contents of pyrrole‐2,3,5‐tricarboxylic acid (PTCA) and pyrrole‐2,3‐dicarboxylic acid (PDCA). We measured age‐dependent increases in the relative quantity of eumelanin in pigmented human hairs in the three ethnic groups. Regarding melanin composition, we observed an increase in the PDCA/PTCA ratio with age in African‐American and Caucasian hairs until approaching the quite constant level of the ratio in East Asian hairs in the elderly individuals. Our results evidence differences in the content and composition of eumelanin in human hair among African‐American, Caucasian and East Asian individuals. Furthermore, we show evidence of age‐dependent changes in the quantity and quality of eumelanin in pigmented human hairs. In particular, the age‐dependent modification of the PDCA/PTCA ratio, a marker for 5,6‐dihydroxyindole units in eumelanin, suggests a chronological evolution of hair follicle melanocyte phenotype (e.g. decrease in dopachrome tautomerase expression).