New thiadiazine derivatives with activity against Trypanosoma cruzi amastigotes

Abstract

Abstract. The cytotoxicity of 18 new 1,2,6-thiadiazin-3,5-dione 1,1-dioxides was evaluated. This group of products was previously assayed against epimastigotes of Trypanosoma cruzi and some of them showed a high antiprotozoal activity. Thereafter 13 compounds with a high anti-epimastigote activity and low cytotoxicity were selected to be assayed against amastigotes. Some of the products showed the same or even lower cytotoxicity than nifurtimox and benznidazole, but most of them were very toxic for macrophages at 100 µg/ml. Only one of the compounds had an anti-amastigote activity similar to that of reference drugs at 10 µg/ml, but unfortunately this disappeared at lower concentrations.Chagas' disease is a major health problem in South and Central America, affecting 16-18 million people (WHO 1991). In spite of such high prevalence, only two synthetic compounds, nitroheterocycles nifurtimox (Lampit ® ) and benznidazole (Rochagan ® ), are in use (Croft et al. 1997). Both are effective in the early stages of trypanosomiasis, but are practically useless in the chronic disease. Only 50% of patients are parasitologically healed after treatment (Kirchhoff 1994). The limited efficacy as well as their toxic side effects justify the continued research for trypanocidal substances.In this way, new 1,2,6-thiadiazine-3,5-dione 1,1-dioxides have been synthesised (Di Maio et al. 1999). In previous works were reported the anti-Trypanosoma cruzi properties of 3,5-diamino-4-(5'-nitro-2-furfurylidene) 4H-thiadiazine 1,1-dioxide and those of some 4-heteroarylidene-1,2,6-thiadiazine-3,5-dione 1,1-dioxide . The presence of nitro substituents in the pentaheterocyclic moiety, as a source of free radicals, seems to be a factor that increases anti-T. cruzi activity (Di Maio et al. 1999).Previous anti-T. cruzi activity of these new thiadiazines was evaluated on epimastigotes. Almost all of them were effective at 100 µg/ml. Some of them remained active at 10 µg/ml (3a, 3b, 3c, 3d, 4a, 4b, 4c and 4d), but none at 1 µg/ml (Di Maio et al. 1999). After the first screening, new in vitro studies have been performed to analyse the nonspecific toxicity and antiamastigote activity of the compounds. MATERIALS AND METHODSCell culture. Murine J774 macrophages were grown in plastic 25ml flasks in RPMI 1640 medium (Sigma) supplemented with 20% heat inactivated (30 min, 56ºC) foetal calf serum (FCS) and 100 IU penicillin/ml + 100 µg/ml streptomycin, in a humidified 5% CO 2 / 95% air atmosphere at 37ºC and subpassaged once a week.Parasites. Trypanosoma cruzi Chagas, 1909 (Y strain) was grown at 28ºC in liver infusion tryptose (LIT) supplemented with 10% FCS and antibiotics. Epimastigote forms were harvested on day 14 of culture (stationary phase) and washed three times in Grace medium. To induce metacyclogenesis, parasites were then cultured in fresh Grace medium supplemented with 10% FCS and haemin (25 µg/ml). Nine days after cultivation at 28ºC, metacyclic forms were counted in order to infect macrophages. The proportion of metacyclic forms was around 30...

A Critical Review on Chagas Disease Chemotherapy

“…Among the less cytotoxic derivatives of the second series, one compound showed activity against intracellular amastigotes similar to the standard drug (Muelas et al 2001).…”

In VitroAntiparasitic Activity of Plant Extracts from Panama

“…The cells were allowed to attach for 24 h at 37°C in atmosphere with 5% CO 2 in air, and then exposed to the extracts for another 24 h. Afterwards, cytotoxicity was determined by addition of MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazlium bromide] as previously (Muelas et al, 2001).…”

5-Nitro-2-furyl derivative actives against Trypanosoma cruzi: Preliminary in vivo studies

“…In this way, new 5-nitro-2-furyl derivatives have been synthesized [6][7][8][9][10]. Previously, were reported the anti-Trypanosoma cruzi properties in vitro and in vivo of some of these derivatives [11,12]. It was also demonstrated that the presence of a nitro moiety, as a source of free radicals, seems to be a feature that increases the anti-T. cruzi activity [13].…”