Probing the interaction of kojic acid antibiotics with iron(III) chloride by using electrospray tandem mass spectrometry

Kojic acid, 5‐hydroxy‐2‐(hydroxymethyl)‐4H‐pyran‐4‐one, has been used extensively as a clinical iron‐chelating drug although the nature of the complexes of iron and kojic acid has not been established. In this article we demonstrate the complexation of kojic acid with iron(III) chloride by using electrospray ionization mass spectrometry (ESI‐MS). The ESI‐MS analysis revealed different reactions between iron(III) chloride and kojic acid (M), and the mass spectrum exhibited four complexes: [Fe+2(MH)]+, [Fe+3(MH)+H]+, [Fe2+4(MH)+Cl]+, and [Fe2+5(MH)]+. All these proposed complexes and the presence of chloride ion in one of the dinuclear complexes have been confirmed by isotopic patterns and fragmentation studies by means of tandem mass spectrometry (MSn). Copyright © 2004 John Wiley & Sons, Ltd.