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BackgroundThe food-borne liver fluke Opisthorchis felineus is an epidemiologically important species and the causative agent of opisthorchiasis across an extensive territory of Eurasia. For decades, treatment of opisthorchiasis has been based on praziquantel. Tribendimidine could be an alternative drug that has been successfully tested for Opisthorchis viverrini and Clonorchis sinensis infections. We aimed to assess tribendimidine effects in comparison with praziquantel in vivo and in vitro against the liver fluke Opisthorchis felineus.ResultsIn this study we (i) calculated half-maximal inhibitory concentrations (IC50) by motility tests against O. felineus adults and newly excysted metacercarie after tribendimidine treatment in vitro; (ii) determined whether tribendimidine and PZQ effects on adult liver flukes are dependent on or mediated by white blood cells; and (iii) tested in vivo the anthelmintic activity of tribendimidine on juvenile and adult worms. We found that the efficiency of tribendimidine in vitro was similar (IC50 = 0.23 μM for newly excysted metacercariae and 0.19 μM for adult worms) to that of praziquantel (IC50 0.98 μM for newly excysted metacercariae and 0.47 μM for adult worms). The treatment of adult worms in vivo with praziquantel or tribendimidine at 400 mg/kg resulted in a 76% and 77.2% reduction, respectively, in the worm burden during chronic infection.ConclusionsThe differences between WBR values after PZQ and TBN treatment were not significant, thus tribendimidine was as effective as praziquantel against O. felineus liver flukes. Given the broad-spectrum activity of tribendimidine and efficacy against O. felineus, this drug may be a promising candidate for the treatment of opisthorchiasis felinea and other liver fluke infections.

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Heating of benzofurazans with ethanolamine in the presence of catalytic amount of p toluenesulfonic acid leads to quinoxalines.Study of chemical properties of benzofurazans showed that the heating of compounds 1a-g with ethanolamine at 150-170 °C in the presence of catalytic amount of p toluenesulfonic acid unexpectedly leads to quinoxalines 2a-g (Scheme 1).It should be noted that the reaction of ben zo[1,2 c:3,4 c´]difurazan 1e proceeds with generation of Scheme 1 1, 2: R 1 = H, R 2 = H (a), Me (b), MeO (c); R 1 = NH 2 , R 2 = H (d); R 1 + R 2 = (e), N N N Ph (f), -CH=CH-CH=CH-(g) Scheme 2 Scheme 3heat and leads to furazano[4,5 f]quinoxaline 2e in 76% yield. Upon further heating of compound 2e with ethanol amine at 150 °C, a reduction of its furazan ring takes place to form 5,6 diaminoquinoxaline 3 (Scheme 2).