UV-vis and electrical impedance characterizations of the hydroxychloroquine-zinc complex in the phospholipid-like oleic acid phase

Abstract

• Investigating properties of hydroxychloroquine-Zinc complex in hydrophobic oil. • UV-vis and impedance spectroscopies identified stable complex formation. • Efficiency of complex migration across water-oil interface was analyzed. • The complex polarization reduced signal energy loss inside oil. • Facile impedance measurement to confirm hydroxychloroquine as Zn ionophore. • The work is interesting for both fundamental biophysics and COVID-19. UV-vis and impedance measurements were performed to determine the stable formation of the Hydroxychloroquine-Zinc (HCQ-Zn) complex within the oleic acid (oil) phase of the oil-water system. Decreased UV absorbance with increased Zn concentration was associated with the gradual formation of the complexes within the oil phase, agreeing with existing reports and our time-dependent-density-functional calculations. The reproducibility of our data over a long period indicates the stability of the complex within the oil phase. The impedance measurement showed that the dielectric loss of the oil phase due to the polarization of the complex is less than that due to the polarization of HCQ. A basic impedance measurement revealed that the aqueous-to-oil transfer of Zn is not possible without the HCQ, a result pertinent to the recent report that HCQ is Zn ionophore. Our work is thus important to the fundamental physical chemistry and the current COVID-19 issue where the Zn infusion across the living cell phospholipid membrane (mimicked as an oil-water interface) reduces viral replication.