Accepted Article This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/pcmr.12673 This article is protected by copyright. All rights reserved. DR. SHOSUKE ITO (Orcid ID : 0000-0001-9182-5144) PROF. KAZUMASA WAKAMATSU (Orcid ID : 0000-0003-1748-9001) Article type : Original Article Manuscript Category: Melanin Chemistry & Pigmentation (MCP) Original Article: Melanin Chemistry & Pigmentation Acid hydrolysis reveals a low but constant level of pheomelanin in human black to brown hair Shosuke Ito 1 , Shiho Miyake 2 , Shoji Maruyama 2 , Itaru Suzuki 2 , Stéphane Commo 3 , Yukiko Nakanishi 1 and Kazumasa Wakamatsu 1 1 Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan 2 Nihon L’Oréal, R&I, Kawasaki, Japan 3 L’Oréal Research and Innovation, Aulnay-sous-Bois, France Correspondence: Shosuke Ito, Tel +81-562-93-2595; Fax +81-562-93-4595; e-mail: sito@fujita-hu.ac.jp Summary We previously reported a constant ratio of the benzothiazole-pheomelanin marker thiazole-2,4,5-tricarboxylic acid (TTCA) to the eumelanin marker pyrrole-2,3,5-tricaboxylic acid (PTCA) in eumelanic, black human hair. A constant level (20-25%) of benzothiazole-type pheomelanin was recently demonstrated in human skin with varying concentrations of melanin. Therefore, in this study, we aimed to investigate the origin of pheomelanin markers in black to brown human hair by developing a method to remove protein components from hair by heating with 6 M HCl at 110˚C for 16 h. For comparison, synthetic melanins were prepared by oxidizing mixtures of varying ratios of dopa and cysteine with tyrosinase. Hair melanins and synthetic melanins were subjected to acid hydrolysis followed by alkaline H 2 O 2 oxidation. The results show that the hydrolysis