Evaluation of toxicity of benzimidazole derivatives and their effect on functional parameters of Ceriodaphnia dubia Richard, 1894

Recently due to active development of the pharmaceutical industry, an acute problem of environmental pollution with synthetic biologically active compounds has arisen. Benzimidazole cycle is one of the most frequently encountered pharmacophores in drugs. Substances containing even microquantities of benzimidazole have a toxic effect on living systems. Besides, being alien to nature, benzimidazoles are not included in metabolic processes and do not decompose for a long time. Evaluation of benzimidazole toxicity, its stability in the aquatic environment, benzimidazole impact on biological pammeters will make it possible to predict possible changes in the populations of ceriodaphnia and other aquatic organisms. The purpose of the work is to evaluate the toxicity of benzimidazole derivatives and their effect on the survival and fertility of Ceriodaphnia dubia Richard, 1894. Materials and Methods. In acute and chronic experiments, the authors determoined parameters standard for toxicological studies: median lethal concentrations (LC50), life expectancy, total number of offspring, number of litters per female, and average hatching time. The stability of the toxicity of benzimidazole derivatives was established in terms of Ceriodaphnia dubia lethality during a 30-day exposure. Results. The authors evaluated the toxicity of benzimidazole and its seven derivatives for ceriodaphnia in terms of the 48-hour median lethal concentration, depending on their structure. The highest toxicity was noted for 5-bromo-2-(trifluoromethyl)-1H-benzimidazole (LC50 2.4 mg/l), the lowest one for 2-methyl-1H-benzimidazole (LC50 109.7 mg/l). It has been shown that long-term exposure (38 days) to potassium salt of pyrido[1,2-a]benzimidazole-7-carboxylic acid (LC50 69.18 mg/l) at a concentration of 20 mg/l in a chronic experiment does not lead to a statistically significant change in survival and fertility parameters of cerio-daphnia. Stability evaluation of toxicity of the potassium salt of pyrido[1,2-a]benzimidazole-7-carboxylic acid and residual toxicity of its degradation products revealed a relatively low stability of the compound toxicity. Conclusion. The toxicological evaluation of benzimidazole derivatives for hydrobionts showed the correlation between the degree of their toxicity and structural features.