SYNTHESIS AND ANTINEMATODAL ACTIVITY STUDIES OF SOME FUSED TRIAZINOBENZIMIDAZOLES

. 4-Aryl-3,4-dihydro[1,3,5]triazino[1,2-a]benzimidazole-2-amines 3a-f were synthesized in the reaction of cyclocondensation between 2-guanidinobenzimidazole and versatile benzaldehydes. Structures of all prepared compounds were confirmed by IR, 1 H NMR spectroscopy and elemental analysis. Antinematodal activity in vitro of the substances was investigated using isolated Trichinella spiralis muscle larvae. The tested triazonobenzimidazoles showed different activity depending on the substituent R in their molecule as the derivatives substituted with a hydroxyl group demonstrated the best anti-Trichinella spiralis activity in the series.

Introduction.Parasitic diseases are a global health problem in developing countries with tropical and subtropical climates.In the countries of Eastern Europe, including Bulgaria, regardless of the results achieved in the control of parasitosis, the problem of radical treatment of some of the common intestinal and tissue helminthiasis (e.g.trichinosis, echinococcosis, fasciolosis, filariasis, etc.) is not solved.In clinical practice, drugs from the benimidazole group such as albendazole, mebendazole, thiabendazole and flubendazole are widely used [1,2] but the anthelmintic resistance in parasites is now widespread [3].For this reason, there is a need for new drugs for the treatment and control of helminth infections.Promising results from pharmacological studies on the anthelmintic activity of benzimidazole derivatives [4][5][6][7] determine the increased interest in the synthesis and study of new benzimidazole compounds as potential antinematodal agents.The binding of different pharmacophores into a single molecule would lead to the generation of new compounds, which have a synergistic effect on parasites.
Aim.The aim of the present study is the design and synthesis of compounds combining in one molecule two pharmacophores -benzimidazole and 1,3,5-triazine nucleus, as potential antinematodal agents against the larvae of the Trichinella roundworm.
Materials and Methods.All chemicals were purchased from commercial suppliers.The IR spectra were taken in a KBr tablet on a Varian apparatus or recorded by ATR on a Bruker Equinox 55 spectrophotometer. 1 H-NMR spectra were taken on a Bruker Avance AV 600 (Bruker, Faelanden, Switzerland).Chemical shifts are expressed in terms of tetramethylsilane (TMS) and are presented in δ (ppm) using deuterated DMSO as solvent.The microanalyses for C, H and N were performed on Perkin-Elmer elemental analyzer.Analyses indicated by the symbols of the elements or functions were within ±0.4% of the theoretical value.All compounds were routinely checked by thin layer chromatography (TLC) using on ALUGRAM SIL G/UV254 pre-coated aluminium sheets with silica gel 60, 0.20 mm thick (Macherey-Nagel, Germany) and the spots were detected under UV light (254 nm).

Anthelmintic evaluation assay
The bioassay previously reported by us [4] was used without modifications: encapsulated Trichinella spiralis muscle larvae, 100 specimens per 1 mL physiological solution were used; the triazinobenzimidazole derivatives tested were dissolved in DMSO and their concentration is shown in Table 1.The samples were incubated in thermostat at a temperature of 37 °C.Control microscopic observation for the viability of Trichinella larvae was performed after 24 and 48 hours.
The experimental results, summarized in Table 1, allowed the identification of compound 3f as the most potent anthelmintic agent (56% efficacy at a concentration 50 μg/ml after 24 hours).