Nuclear Magnetic Resonance Studies of 6-hydroxydopamine and Its Interactions with SH-containing Model Compounds. Evaluation of Possible Mechanism for Neurocytotoxicity

6-Hydroxydopamine (I) is a well-known neurocytotoxic agent which has become an important tool in many neurochemical studies in recent years. Biochemical investigations of the mechanism of action of 6-hydroxydopamine indicated that this amine binds covalently and irreversibly to proteins. In the present work, molecular properties of 6-hydroxydopamine in aqueous solution such as self-association, ionization, intramolecular conformations, and possible cyclization were investigated using 1H nuclear magnetic resonance spectroscopy. A model study for the interaction of 6-hydroxydopamine with proteins was undertaken by using SH-containing molecules: cysteine, glutathione, and bovine serum albumin. The binding of these compounds to 6-hydroxydopamine was found to cause labilization of the hydrogen attached to C2 of the amine aromatic ring. This effect was interpreted in terms of nucleophilic attack of RS- on C1 of 6-hydroxydopamine. A proposed model for neurocytotoxicity is discussed.