Synthesis And Antibacterial Application Of Novel Pyridinium-N-Halamine Biocides

In recent years, the environment deterioration and the spread of pathogenic microorganisms have lead to frequent public safety health incidents, which greatly threaten people’s daily life and property safety. Therefore, the development of highly effective antibacterial agents and antimicrobial materials is of great significance in order to reduce the influence of pathogenic microorganisms on the food, water and health et al.N-Halamine antibacterial agents are used widely due to high bactericidal efficacy, bactericidal broad-spectrum, rechargeable antibacterial function and other advantages, but their hydrophilicity decreased after chlorination. Introducing quaternary ammonium structure to the N-Halamine by Li Lingdong and his colleagues can effectively improve the hydrophilcity of N-Halamines. What’s important that, the introduced cation can greatly enhance antibacterial activity of the N-Halamines. Given the consideration, we firstly designed and totally synthesized novel pyridinium-N-Halamines which combined N-Halamine structure unit and pyridinium salt structure via covalent bond.(1) In this thesis, four pyridinium-N-Halamine compounds with different hydrophobic chain length were synthesized with 5,5-dimethyl hydantoin as the starting material by N-alkylation, quaternization, and chlorination. Structures of all compounds were confirmed by 1HNMR and 13C NMR.(2) The antimicrobial activity of prepared pyridinium-N-Halamine against E. coli ATCC 25922 was performed by shaking flask method. The effects of ionic moiety structure and the length of hydrophobic chain on antimicrobial activity were discussed. Experimental results indicated that the antimicrobial activity of pyridinium-N-Halamines were much stronger than the reported quaternium-N-Halamines, probably due to the more concentrated positive charge of pyridinium structure; With the increase of hydrophobic chain length between N-Halamine moiety and quaternary ammonium salt moiety, the antimicrobial activity of pyridinium-N-Halamines reduced firstly and then increased. When the length of the alkyl chain reaches to 12-CH2-, the antimicrobial activity was the highest among all the tested samples:in presence of 20 ppm active chlorine 2.14 log reductions of E. coli ATCC 25922 (1.66×106 CFU) was realized within 5 min. The observed resluts was probably caused by the hydrophilcity decreases as the chain length increases from 3-CH2-units to 8-CH2-units, and by the little contribution of the linker chain which are not capble of penetrateing the bacterial cell membrane. However, when the hydrophobic chain length was 12 -CH2- units, the pyridinium salt exhbited distinct antibacterial activity because of the long linker chain which could break through cell membrane at this point, although the hydrophilcity of this biocide molecule (Compound 16) is still not good as the biocide molecule with 3 -CH2- units (Compound 13)(3) In addition, taking 3-hydroxypyridine as the starting material, a pyridinium-N-Halamine precursor with bonding group-siloxane structure was totally synthesized, and the structure was successfully confirmed by NMR data. The resulting pyridinium-N-Halamine precursor could be easily immobilized on cotton fabric surface which will be carried out in near future.