Anthelmintics used for intestinal helminthiasis treatment are generally effective;
however, their effectiveness in tissue parasitosis (i.e. visceral toxocariasis) is
moderate. The aim of this study was to evaluate the in vitroactivity
of lapachol, β-lapachone and phenazines in relation to the viability of
Toxocara canis larvae. A concentration of 2 mg/mL (in duplicate)
of the compounds was tested using microculture plates containing Toxocara
canis larvae in an RPMI-1640 environment, incubated at 37 °C in 5%
CO2 tension for 48 hours. In the 2 mg/mL concentration, four
phenazines, lapachol and three of its derivatives presented a larvicide/larvistatic
activity of 100%. Then, the minimum larvicide/larvistatic concentration (MLC) test
was conducted. The compounds that presented the best results were nor-lapachol (MLC,
1 mg/mL), lapachol (MLC 0.5 mg/mL), β-lapachone, and β-C-allyl-lawsone (MLC, 0.25
mg/mL). The larvae exposed to the compounds, at best MLC with 100% in
vitro activity larvicide, were inoculated into healthy BALB/c mice and
were not capable of causing infection, confirming the larvicide potential in
vitro of these compounds.
Human toxocarosis is a chronic tissue parasitosis most often caused by Toxocara canis. The seroprevalence can reach up to 50%, especially among children and adolescents. The anthelmintics used in the treatment have moderate efficacy. The aim of this study was to evaluate the in vitro and in vivo anthelmintic activity of quinones and their derivatives against T. canis larvae and the cytotoxicity of the larvicidal compounds. The compounds were evaluated at 1 mg mL(-1) concentration in microculture plates containing third stage larvae in an Roswell Park Memorial Institute (RPMI) 1640 environment, incubated at 37 °C in 5% CO2 tension for 48 h. Five naphthoxiranes were selected for the cytotoxicity analysis. The cell viability evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays using murine peritoneal macrophages isolated from C57BL/6 mice revealed that the naphthoxiranes (1 and 3) were less cytotoxic at a concentration of 0.05 mg mL(-1). The efficacy of naphthoxiranes (1 and 3) was examined in murine toxocarosis also. The anthelmintic activity was examined by evaluating the number of larvae in the brain, carcass, liver, lungs, heart, kidneys and eyes. Compound (3) demonstrated anthelmintic activity similar to that of albendazole by decreasing the number of larvae in the organs of mice and thus could form the basis of the development of a new anthelmintic drug.
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