Allyl rhodanine azo dye derivatives: Potential antimicrobials target d-alanyl carrier protein ligase and nucleoside diphosphate kinase

3-Allyl-5-(4-arylazo)-2-thioxothiazolidine-4-one (HLn) ligands (where n=1 to 3) were hypothesized to have antimicrobial activities mediated through inhibition of new antimicrobial targets. The ligands (HLn) were synthesized and characterized by infrared (IR) and H-1 nuclear magnetic resonance (H-1 NMR) spectra. The ligands (HLn) were in silico screened to their potential inhibition to models of d-alanyl carrier protein ligase (DltA) (from Bacillus cereus, PDB code 3FCE) and nucleoside diphosphate kinase (NDK) (from Staphylococcus aureus; PDB code 3Q8U). HL3 ligand has the best energy and mode of binding to both NDK and DltA, even though its binding to DltA was stronger than that to NDK. In antimicrobial activity of HL3 ligand, morphological and cytological changes in HL3-treated bacteria agreed with the in silico results. The HL3 ligand showed significant antimicrobial activity against B. cereus, S. aureus, and Fusarium oxysporium. The HL3-treated bacterial cells appeared malformed and incompletely separated. Its cell walls appeared electron-lucent and ruptured. They contained more mesosomes than normal cells. It was found that the HL3 ligand represented as a bactericide against B. cereus and S. aureusby blocking target DltA, and may target NDK.