Relative fluorescence intensities of human plasma soluble melanins in normal adults.

Fluorescence spectroscopy of plasma soluble melanin derived from 3-hydroxyanthranilic acid discloses an emission (em) maximum at approximately 413 nm [excitation (ex) maximum approximately 324 nm]; plasma melanins derived from dopa, catecholamines, catechol and 3-hydroxykynurenine have em maxima at approximately 445 nm (ex maxima approximately 345 nm). All of these melanins are present in human plasma. For the present study, plasma samples were obtained from 120 healthy Caucasian, Hispanic, Mongoloid and Negroid males and females, ranging from 19 to 92 years of age, with 12 or more subjects in each racial and sex group. The average relative fluorescence intensities of all samples (diluted 1 to 50 with water) were 34.6 +/- 7.4 (standard deviation) at 413 nm and 40.8 +/- 8.2 at 445 nm. Individual intensity values in samples from women below 50 years in age were in the lower range of the values observed; at age 50 and higher no difference was seen in samples from women and men. No clear cut relationships to race or age were seen.