Complexation of Gold(III) with Pyridoxal 5′-Phosphate-Derived Hydrazones in Aqueous Solution

Abstract

Today, complexes of gold(I) and gold(III) are recognized as promising drugs for the treatment of bacterial infectious diseases and oncological diseases, respectively. It is of interest to broaden the area of potential use of gold(III) compounds to the pathogenic microorganism as well. The first step towards the development of new antibacterial drugs based on Au3+ complexes is the study of their stability in an aqueous solution. The present contribution reports on the investigation of gold(III) complexation with five hydrazones derived from a well-known biologically active compound, pyridoxal 5′-phosphate (one of the aldehyde forms of the B6 vitamin). The complex formation in aqueous solutions was confirmed by mass spectrometry and fluorescent spectroscopy. The stoichiometric composition of the complexes formed and their stability constants were determined using a UV–Vis titration method. The complexes are quite stable at physiological values of pH, as the speciation diagrams show. The results of the paper are helpful for further studies of gold(III) complexes interaction with biomacromolecules.

Complexes of Gold(III) with Hydrazones Derived from Pyridoxal: Stability, Structure, and Nature of UV-Vis Spectra

“…The reasoning described in our previous paper [39] devoted to the gold(III) complexation with PLP-derived hydrazones is also applicable to the complexation with pyridoxalderived ligands. During the titration, the pH value changed from 3.3 to 9.8 units, which did not cause the precipitate formation.…”

“…Our previous papers [39,40] were devoted to the study of the stability and structure of several gold(III) complexes with hydrazones derived from pyridoxal 5′-phosphate. PLP-derived hydrazones have received less attention with regard to their biological activity than PL hydrazones.…”

“…Our previous papers [39,40] were devoted to the study of the stability and structure of several gold(III) complexes with hydrazones derived from pyridoxal 5 ′ -phosphate. However, some questions remained unanswered.…”

“…Therefore, the present contribution aims to (1) clarify the possible role of the phosphate group in the complexation of B 6 vitamin-derived hydrazones with gold(III) species. To figure out the phosphate effect, it is convenient to study the complexation of gold(III) with pyridoxal hydrazones that are analogous to the PLP derivatives described earlier [39]. (2) Achieve a better agreement between the calculated and experimental UV-Vis spectra for different protonated complexes.…”

Design and Synthesis of Novel Antimicrobial Agents

“…Given its two essential functions in metabolism and iron acquisition, the E4PDH enzyme from A. baumannii may be critical in bacterial pathophysiology [ 128 ]. In addition to vitamin B6 derivatives, metals such as gold [ 130 ], nickel, copper [ 131 ] and gallium [ 132 ] are employed. Metal complexes were investigated for their potential antibiotic efficacy against various bacterial strains, and the results against resistant bacteria were encouraging.…”