Antibacterial and antifungal activities in vitro of a novel silver(I) complex with sulfadoxine-salicylaldehyde Schiff base

Abstract

Skin wound infections can be considered one of the most common causes of death in burned patients. The raising reports of multidrug resistant microorganisms reveals a complicated condition for the treatment of burn wound injuries, establishing urgency in the development of novel antimicrobial agents. Considering this scenario, the present work describes the synthesis, antibacterial and antifungal activities of a sulfadoxine-salicylaldehyde Schiff base (SFX-SL), and of its novel dimeric silver(I) complex (AgSFX-SL). Elemental analysis indicated a 1:1 metal:ligand molar composition for the AgSFX-SL complex, with the minimum formula AgC19H17N4O5S. Mass spectrometric (HRMS) data reveal the existence of dimeric species of the complex in solution. Infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic studies suggest coordination of the Schiff base to silver(I) by the nitrogen and oxygen atoms of the sulfonamide group. The structure of the SFX-SL Schiff base was determined by single crystal X-ray diffraction. Molecular modeling confirms the proposition of a dimeric structure for the AgSFX-SL complex as early indicated by mass spectrometric data. The AgSFX-SL complex showed an effective antimicrobial activity over pathogens including Gram-positive Staphylococcus aureus (multidrug resistant), S. epidermidis, Cutibacterium acnes, and Gram-negative Pseudomonas aeruginosa and Burkholderia cepacia, with minimum inhibitory concentration (MIC) values in the range 12.0–48.0 µmol·L−1. Additionally, the AgSFX-SL complex was active against Candida albicans with a MIC value of 2.8 µmol·L−1. Electrophoresis assays showed that the AgSFX-SL complex does not interact with protein models lysozyme and bovine serum albumin (BSA).