Abstract
The use of antibacterial medication is one of the greatest discoveries of the pharmaceutical industry. However, the overuse and misuse of these compounds have led to bacterial pathogens developing resistance to them and rendering previously effective antimicrobial drugs ineffective. This phenomenon is known as Antimicrobial Resistance (AMR) and is forecasted to reach a death toll of 10 million by 2050. In response to this, Schiff base compounds have been considered as possible therapeutic candidates for antibacterial and anticancer applications. This dissertation was focused on studying the influence that halogen and alkyl substituents have on the biological activity that Schiff base compounds express, as well as how their respective Schiff base-derived Pd(II) complexes compare.
The Schiff base compounds were synthesised using salicylaldehyde or halogen-substituted salicylaldehyde and aniline or alkyl-substituted aniline derivatives. The compounds were then complexed onto Pd(II) using Pd(OAc)2 as the complexing agent. The synthesis of the Schiff base compounds and their respective Pd(II) complexes was confirmed using various spectroscopic and analytical techniques, including melting-point determination, ¹H and ¹³C NMR spectroscopy, CHN elemental analysis, FTIR, UV-Vis spectroscopy, HR-MS, and SC-XRD.
The crystallographic data obtained indicated that the Schiff base ligands are bidentate and bind onto the Pd(II) metal cation in a trans-N,N’ and -O,O’ arrangement. Stability testing revealed that the Schiff base compounds and their respective complexes do not all show appreciable levels of stability, with iodine and tert-butyl substituted compounds (S4/C4 & S7/C7) showing the best sample stability.
Cytotoxicity analysis of the Schiff base compounds and their respective complexes was conducted using the MTT assay. The Schiff base compounds did not exhibit appreciable cytotoxicity against the ME180 cell line, showing greater cytotoxicity only at lower concentrations. The Schiff base complexes, however, displayed improved cytotoxicity but also showed reduced efficacy at higher concentrations. The best-performing compounds were the isopropyl- and chlorine-substituted Schiff base compounds and Pd(II) complexes.
Antioxidant analysis was conducted using both the ABTS and DPPH assays. Results from the DPPH assay show that the Schiff base compounds had greater radical scavenging activity ...