Magnetic beads method for determination of binding of drugs to melanin.

Binding to melanin is considered to be a reason for several adverse effects of drugs and should be known to reduce the failure rate due to inappropriate pharmacokinetics in search for better pharmaceuticals. A new, reliable and convenient method of determination of affinity of drugs and drug candidates to melanin has been proposed employing magnetic beads. For that aim the reaction conditions to effectively covalently immobilize melanin on surface of superparamagnetic beads have been determined. Binding efficiency of melanin towards antipsychotic and other basic drugs has been determined and compared to that obtained in the affinity HPLC systems employing aminopropylsilica stationary phases with immobilized melanin. The magnetic beads method provided melanin binding data correlating well with the ability of agents to evoke extrapyramidal symptoms. Quantitative structure-property relationships have been derived describing the melanin binding efficiency in terms of structural descriptors of drugs from calculation chemistry. Thus, an approach has been proposed to evaluate a priori melanin binding potency of drug candidates based solely on their chemical formula.