The study of the antihypoxic activity of new derivatives of benzilic acid

On the model of acute normobaric hypoxic hypoxia with hypercapnia the antihypoxic action of new derivatives of benzilic acid, namely – N-heterylamides of benzilic acid and products of their intramolecular cyclodehydration – thienolactams with five-, sixand seven membered cycles, respectively. Amides have also been studied on the basis of five-membered lactam – derivatives of thieno[3,4-b]pyrrol6-carboxylic acid. According to the result of our studies the following regularities have been found. The cyclization products of benzilic acid amides significantly exceed the antihypoxic activity of the parent compounds, and it indicates the prospects of conducting the studies among the products of heterocyclization of Nheterylamides of benzilic acid. It should also be noted that modification of the ester group in position 6 of 2-oxo-3,3-diphenyl-2,3-dihydro-1Н-thieno[3,4-b]pyrrole-6-carboxylic acid appeared to be appropriate. Amides based on this compound (KMS-68, KMS-69, KMS-71) during the experiment showed the maximum life span of the animals under research.

Hypoxia occurs with the lack of oxygen in the inhaled air and blood, as well as in disturbance of the biochemical processes of tissue respiration. Because of this oxygen deficiency the irreversible changes occur in organs. The central nervous system, heart muscle, kidney tissues, and liver are the most sensitive to the lack of oxygen.
To reduce hypoxia pharmacological products the methods that increase the supply of oxygen to the body and improve its utilization are used [3,4]. The aim of this work was to determine the antihypoxic activity of the new pharmacologically active compounds synthesized in the range of benzilic acid derivatives.

Materials and Methods
The object of the study of the antihypoxic action was the new group of compounds of benzilic acid derivatives synthesized at the Organic Chemistry Department of the National University of Pharmacy, namely -N-heterylamides of benzilic acid and products of their intramolecular cyclodehydration -thienolactams of five-, sixand seven membered cycles, respectively. Amides also were studied on the basis of five-membered lactamderivatives of thieno[3,4-b]pyrrol-6-carboxylic acid.
The studies of the antihypoxic activity of new derivatives of benzilic acid were conducted on the model of acute normobaric hypoxic hypoxia with hypercapnia (ANHHH). Determination was conducted according to the guidelines "Preclinical studies of drugs" edited by O.V.Stefanov in outbred mice weighing 20-26 g; they were kept in the vivarium of the Central Research Laboratory of the National University of Pharmacy in standard conditions on a normal diet with free access to food and water [5]. Animals were divided into 17 groups; 5 mice in each group. Animals in the groups under research received once an aqueous solution of the substance studied orally by gavage in the dose of 12 mg/kg 60 min before the experiment. Control animals were injected with the corresponding volume of saline. ANHHH was modelled by placing the mice in isolated containments. The observation lasted until the death of animals [1, 6, 7].
The antihypoxic activity was assessed by the life span (min) in relation to the control taken as 100% by the formula: where: AA -is the antihypoxic activity (%); t d -is the life span of the experimental animals; t k -is the life span of control animals [2].
The statistical processing of the research results was performed using Student's t-test. Differences were considered significant at p<0.05.

Results and Discussion
The data obtained in the study of the antihypoxic activity of the new pharmacologically active compounds synthesized in the range of benzilic acid derivatives are given in Table and Fig It should be also noted that when introducing the original methyl ester (KMS-10) to the group of experimen- tal animals there was decrease of the antihypoxic activity by 3.70%, and introduction of the six-membered cycle thienolactam (KMS-303), unlike seven-membered lactams, led to 1 min reduction of the life span of laboratory mice.
The analysis of statistically processed data concerning survival in ANHHH of laboratory animals showed that the most effective substances were KMS-68, KMS-69,  Thus, according to the result of our studies the following regularities have been found: the cyclization products of benzilic acid amides significantly exceed the antihypoxic activity of the parent compounds. This tendency is observed in pairs: KMS-10 -KMS-19, KMS-228 -KMS-229, KMS-230 -KMS-258, and indicates the prospects of conducting the studies exactly among the products of heterocyclization of N-heterylamides of benzilic acid. It should also be noted that modification of the ester group in position 6 of 2-oxo-3,3-diphenyl-2,3-dihydro-1Н-thieno[3,4-b]pyrrole-6-carboxylic acid appeared to be appropriate. Amides based on this compound (KMS-68, KMS-69, KMS-71) during the experiment showed the maximum life span of the animals under research. A slightly inferior activity was observed for seven-membered thienolactams -5-oxo-6,6-diphenyl-5,6-dihydro-4Н-2-thia-4-asa-benzo[e]azulen-3-methylcarboxylates. Introduction of the chlorine atom in position 8 of the molecule resulted in an insignificant loss of the activity of compound KMS-258 compared to compound KMS-229. CONCLUSIONS 1. On the model of acute normobaric hypoxic hypoxia with hypercapnia the antihypoxic activity of 16 new derivatives of benzilic acid have been studied.