Curcuminoids as potential new iron-chelating agents: spectroscopic, polarographic and potentiometric study on their Fe(III) complexing ability
2002; Elsevier BV; Volume: 328; Issue: 1 Linguagem: Inglês
10.1016/s0020-1693(01)00687-9
ISSN1873-3255
AutoresMarco Borsari, Érika Ferrari, Romano Grandi, Monica Saladini,
Tópico(s)Free Radicals and Antioxidants
ResumoThe pKa values of curcumin and diacetylcurcumin are, here doubtless, determined by means of spectroscopic and potentiometric measurements, and the enolic proton is the more acidic one. The interaction of Fe3+ with curcumin and diacetylcurcumin, in water/methanol 1:1 solution, leads to the formation of the complex species [FeH2CU(OH)2] and [FeDCU(OH)2] (H2CU and DCU=curcumin or diacetylcurcumin monoanion, respectively) which prevails near pH 7. At more basic condition the prevailing species are [FeH2CU(OH)3]− and [FeDCU(OH)3]−, which prevent metal hydroxide precipitation. 1H NMR data state that the dissociated β-diketo moiety of the ligands is involved in metal chelation. The pKa value of the deprotonation reaction is strongly anticipated by the metal ion, as shown by UV spectral data. The stability constants, evaluated from potentiometric data, are near to that of desferrioxamine, which is, by now, the only iron-chelating agent for clinical use.
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