Kinetic studies on the manganese(II) complex catalyzed oxidation of epinephrine

The manganese complex [Mn2(HL)2](BPh 4)2 was found to be a selective catalyst for the oxidation of epinephrine (a catecholamine derivative) to adrenochrome at room temperature in sodium carbonate-bicarbonate buffer. The epinephrine auto-oxidation rate significantly increases upon the addition of manganese complex. The kinetics of reaction was studied by spectrophotometric method, monitoring the increase in concentration of adrenochrome product. According to the proposed mechanism, O2 binding to the manganese complex is followed by the formation of a ternary catalyst-dioxygen-substrate complex as active intermediate, which decomposes in a rate-determining step, generating the adrenochrome. © 2013 Elsevier B.V.