Antioxidant activity of ionic liquids formed by carnitine and food acids: a correlation between the data of their FRAP assay and their pKₐ values

Abstract

The usage of the restricted open-shell Hartree-Fock (ROHF) method to the calculation of electronic structures of the complex Fe(III) with 2,4,6-tripyridyl-s-triazine (TPTZ): [Fe(III)(TPTZ)₂]³⁺ and its adduct with the ionic pair [Carnitine-H]^+ [gentisic acid anion]^- (formed by a protonated carnitine zwitterion and an anion of gentisic acid) allows one to reveal that the anion entering this pair retains its ability to quench free radicals. Antioxidant activity of the studied ionic liquids in their reaction with the complex [Fe(III)(TPTZ)₂]³⁺ is determined by the food acids anions included in their ionic pairs. It is also shown that the values of the antioxidant activity of the studied ionic liquids defined by the FRAP assay correlate with the pKₐ values of their precursor food acids.