Affinity of drugs for dopa-auto-oxidation melanin and tyrosinase-catalyzed dopa-melanin in vitro.

We examined spectrophotometrically the ability of drugs to bind with dopa-auto-oxidation melanin or tyrosinase-catalyzed dopa-melanin. Each drug, at 5 X 10(-5) M, was incubated at 37 degrees C for 8 h with 0.4 mg of synthetic melanins in 20 mM potassium phosphate buffer at pH 7.0 or in 20 mM acetate buffer at pH 4.8. Chloroquine, thioridazine, befunolol, pindolol, daunomycin and 5-fluorouracil bound to melanin at pH 7.0 and 4.8. Methotrexate bound to melanin at pH 4.8, but not at pH 7.0. Pilocarpine, epinephrine, acyclovir, vincristine and colchicine did not bind to dopa-auto-oxidation melanin or tyrosinase-catalyzed dopa-melanin.