Synthesis, biological activities and potential uses of some heterocyclic compounds that can be used in food safety

In this thesis, the synthesis, biological activities and potential uses of some heterocyclic compounds that can be used in ensuring food safety were investigated. Within the scope of the study, isoxazolo-1,4-benzothiazine-4,4-dioxide, isoxazolo-1,4-benzothiazine-4-oxide and benzoimidazoltio acetate derivatives were synthesised. The structures of the synthesised compounds were characterised by Infrared (IR), 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy and High Resolution Mass Spectrometry (HRMS) methods. The antibacterial properties of these compounds were investigated against Gram positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Listeria monocytogenes, Micrococcus luteus) and Gram negative (Escherichia coli, Pseudomonas aeruginosa and Salmonella Typhimurium) bacteria. According to the disc diffusion method, Minimum Inhibitory Concentration (MIC) values of compounds with a large zone of inhibition (>15 mm) were determined. The compounds with this property were isoxazolo-1,4-benzothiazine-4,4-dioxide derivatives and especially one of them (compound 42b) showed high antibacterial activity against Bacillus cereus, Bacillus subtilis and Staphylococcus aureus with large inhibition zone diameter (22-33 mm) and low MIC values (2 µg/mL). Biofilm inhibition and biofilm eradication properties of isoxazolo-1,4-benzothiazine-4,4-dioxide derivatives, whose MIC values were determined, against Bacillus cereus, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus bacteria with high biofilm formation capacity were investigated. Biofilm inhibition at MIC, MIC/2 and MIC/4 concentrations and biofilm eradication properties (removal of formed biofilm) at MIC concentrations of the compounds were investigated. Some of the compounds (42b, 42c and 42f) showed 100% activity against Bacillus cereus, Bacillus subtilis and Staphylococcus aureus in biofilm inhibition studies. On the other hand, many compounds showed low activity against Gram negative bacteria and exhibited high MIC values of >500 µg/mL. The antibacterial and antibiofilm activities of heterocyclic compounds showed high activity especially against Gram positive bacteria, indicating that these compounds may have potential applications in food safety applications.