SPECTROPHOTOMETRIC CHARACTERIZATION OF EUMELANIN AND PHEOMELANIN IN HAIR

Mammalian melanins exist in two chemically distinct forms: the brown t o black eumelanins and the yellow to reddish-brown pheomelanins. They can be quantified by HPLC analysis of pyrrole-2,3,5-tricarboxylic acid (PTCA) and aminohydroxyphenylalanine (AHP). We recently developed a s pectrophotometric method for assaying the total amount of eu- and pheo melanins by dissolving melanins in Soluene-350 plus water. In this stu dy, we examined whether absorbance at 500 nm (A(500)) of the Soluene-3 50 solution reflects the total amount of melanins obtained by the HPLC methods, and whether the ratio of absorbances between 650 and 500 nm reflects the eumelanin/total melanin ratio in mouse hair, sheep wool, and human hair. Our findings were as follows: (1) Total melanin levels calculated from A(500) values correlate well with those obtained from PTCA and AHP values by multiplying with the following factors: for mi ce, PTCA x 45 + AHP x 2.5; for sheep, PTCA x 40 + AHP x 15; and for hu mans, PTCA x 160 + AHP x 10. (2) The A(650)/A(500) ratios were higher (0.25-0.33) in black to brown hair while they were significantly lower (0.10-0.14) in yellow to red hair. These results indicate that (1) th e A(500) value can be used to quantify the total combined amount of eu - and pheomelanins, and (2) the A(650)/A(500) ratio can serve as a par ameter to estimate the eumelanin/total melanin ratio. The present meth od provides a convenient way to qualitatively characterize eu- and phe omelanins in melanins produced in follicular melanocytes.