Relationship of melanin degradation products to actual melanin content: Application to human hair

Methods not only for characterizing but also for quantitating melanin subty pes from the two types of melanin found in hair-eumelanin and pheomelanin-h ave been established, In relation to testing for drugs of abuse in hair, th ese methods will allow for correction of drug binding to specific melanin s ubtypes and will serve to improve drug measurement in hair. 5,6-Dihydroxyin dole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) make up the ma jority of the eumelanin polymer while benzothiazene units derived from S-cy steinyl-S-Dopa (2-CysDopa) and 5-cysteinyl-S-Dopa (5-CysDopa) compose the m ajority of the pheomelanin polymer. Our results show that: (1) pyrrole-2,3- dicarboxylic acid (PDCA) and pyrrole-2,3,5 -tricarboxylic acid (PTCA), mark ers for DHI and DHICA units, respectively, are produced in 0.37 and 4.8% yi elds, respectively, when melanins are subjected to alkaline hydrogen peroxi de degradation, (2) 3-aminotyrosine (3AT) and 4-amino-3-hydroxyphenylalanin e (AHP), markers for 2-CysDopa and 5-CysDopa, respectively, are produced in 16 and 23% yield, respectively, when subjected to hydriodic acid hydrolysi s, and (3) that black human hair contains approximately 99% eumelanin and 1 % pheomelanin, brown and blond hair contain 95% eumelanin and 5% pheomelani n; and red hair contains 67% eumelanin and 33% pheomelanin, These data will allow deeper investigation into the relationship between melanin compositi on and drug incorporation into hair. (C) 2001 Academic Press.