Studies of new biocidal polyguanidines: antibacterial action and toxicity

The aim of this study was to obtain new water-soluble polyguanidines, assess their antimicrobial properties with respect to the test objects of Escherichia coli and Bacillus cereus and establish the hazard class regulated in the territory of the Russian Federation. Polymers obtained in high yields by the method of polycondensation in the melt of the corresponding monomers and characterized by the methods of IR spectroscopy and elemental analysis. Serial dilution–agar plate procedure was performed in order to estimate antibacterial effects. The biocidal properties of the samples were estimated by the percentage reduction of microorganisms (% reduction). To determine the acute toxicity, a toxicometric assessment and symptoms of intoxication upon oral administration of a single dose were carried out in laboratory animals. New water-soluble guanidine-containing polymers with a number average molecular weight of 660–1040 Da were obtained. Copolymers with a low degree of substitution (10–20%) exhibit high antimicrobial activity among N-phenyl-substituted samples. As a result of the substituent increase in the polymer chain, their activity in relation to the studied bacteria is linearly decreased to a level comparable to the test sample. In contrast to the N-octyl-substituted copolymers, gram-positive bacterium B. cereus is more susceptible to N-phenyl-substituted samples. Substances after intragastric injection belong to the fourth class of toxicity (LD₅₀ > 300 ≤ 2000 mg/kg) according to the requirements of tabulation of toxicity classes regulated in the territory of the Russian Federation. The combination of low toxicity with a high level of antibacterial activity of new guanidine-containing polymers suggests the possibility of obtaining new effective disinfectants.