A melanomorph is a substance related to the pigment melanin. Melanomorphs originate from the aromatic amino acids tyrosine, tryptophan, and phenylalanine. They tend to absorb ultraviolet-B light, with peaks around 280 nanometers. See also Beer's Law.
References Organic Chemistry 5th Ed. Bruice http://www.textbookslist.com/sciences/organic-chemistry-5th-edition-paula-y-bruice.html