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Toxocara canis: procura de novos tratamentos na medicina tradicional - estudo in vitro e in vivo
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Com o objectivo de encontrar novos tratamentos para combater o parasita Toxocara canis foram testado,s tanto in vitro como in vivo, produtos naturais usados na medicina tradicional como anti-helmínticos. Assim, foram testados extractos de duas plantas (Chenopodium ambrosioides e Pycnanthus angolensis) e dois suplementos nutricionais (Nutridesintox® e Nutrifibraplus®), sendo o albendazol usado como fármaco de referência. No ensaio in vitro, o Nutridesintox® foi o produto que apresentou maior eficácia na imobilização das larvas de T. canis, seguido dos extractos de hexano e de diclorometano e da infusão de C. ambrosioides. O extracto metanólico, etanólico e de diclorometano obtidos da espécie P. angolensis, não mostraram ter eficácia como anti-helmíntico.
Todavia, os produtos naturais testados exibiram maior actividade biológica contra as larvas de T. canis que o fármaco de referência albendazol.
Tendo como base os resultados obtidos no ensaio in vitro, os suplementos alimentares, a infusão e o extracto de hexano de C. ambrosioides foram escolhidos para testar no ensaio in vivo.
Os produtos naturais foram administrados oralmente a murganhos CD1 experimentalmente infectados com ovos de T. canis. O esquema terapêutico foi iniciado no 10º dia após infecção, numa dose diária, durante três dias consecutivos. A eficácia dos tratamentos foi avaliada, no quinto dia após a última dose de tratamento, através da contagem do número de larvas recuperadas dos tecidos dos murganhos (cérebro, fígado, pulmões e musculatura). Concomitantemente realizou-se a detecção dos anticorpos das classes IgM e IgG pela técnica de ELISA. A dinâmica dos anticorpos nos grupos tratados mostrou ser semelhante ao grupo controlo, não sendo verificadas diferenças estatisticamente significativas. Não houve uma clara redução da carga parasitária nos órgãos dos murganhos dos grupos tratados. O cérebro foi o órgão em que se registou maior densidade de larvas, com a excepção do grupo tratado com a infusão de C. ambrosioides.
Os resultados deste trabalho mostram que a experimentação científica, tendo como base o conhecimento empírico da medicina tradicional, traz mais valias para a descoberta de novos produtos naturais contra a toxocaríase humana. Com base nestes resultados, outros estudos devem ser realizados, para esclarecimento do seu potencial de utilização prática.
The goal of this study was to search for new treatments for Toxocara canis using both in vitro and in vivo experiments. Thus, extracts from two plants (Chenopodium ambrosioides and Pycnanthus angolensis) used in folk medicine as anthelmintic, two dietary supplements (Nutridesintox® and Nutrifibraplus®) and albendazole as standard reference have been tested. In the in vitro experiments the dietary supplement Nutridesintox® was the most effective against T. canis larvae, followed by the hexane and the methylene chloride extracts and the infusion of C. ambrosioides. Opposite results were obtained with the methanolic, ethanolic and the methylene chloride extracts of P. angolensis, which showed no anthelmintic efficacy. Nevertheless, the natural products showed higher biological activity against T. canis larvae than albendazole did. Due to its anthelmintic efficacy the dietary supplements, the hexane extract and the infusion of C. ambrosioides were selected to test in the in vivo experiments. These products were administered orally to T. canis-infected CD1 mice in single doses during three consecutive days, commenced on day 10 post-infection. The efficacy of treatment was evaluated on day 5 after the last dose, by counting the numbers of T. canis larvae in the brain, liver, lungs and muscles and by means of the detection of IgM and IgG antibodies by ELISA technique. The dynamics of the antibodies on the treatment groups showed a similar profile as compared to the control group, statistically significant differences have not been found. The different treatments did not show a clear evidence of reduction of larvae burden in the infected tissues. The level of infection in the brain was higher than in the other organs examined, except for the group treated with the infusion of C. ambrosioides. The in vitro and in vivo results call for further studies on these natural products, in order to find alternative therapeutic regimens for human toxocariasis.
The goal of this study was to search for new treatments for Toxocara canis using both in vitro and in vivo experiments. Thus, extracts from two plants (Chenopodium ambrosioides and Pycnanthus angolensis) used in folk medicine as anthelmintic, two dietary supplements (Nutridesintox® and Nutrifibraplus®) and albendazole as standard reference have been tested. In the in vitro experiments the dietary supplement Nutridesintox® was the most effective against T. canis larvae, followed by the hexane and the methylene chloride extracts and the infusion of C. ambrosioides. Opposite results were obtained with the methanolic, ethanolic and the methylene chloride extracts of P. angolensis, which showed no anthelmintic efficacy. Nevertheless, the natural products showed higher biological activity against T. canis larvae than albendazole did. Due to its anthelmintic efficacy the dietary supplements, the hexane extract and the infusion of C. ambrosioides were selected to test in the in vivo experiments. These products were administered orally to T. canis-infected CD1 mice in single doses during three consecutive days, commenced on day 10 post-infection. The efficacy of treatment was evaluated on day 5 after the last dose, by counting the numbers of T. canis larvae in the brain, liver, lungs and muscles and by means of the detection of IgM and IgG antibodies by ELISA technique. The dynamics of the antibodies on the treatment groups showed a similar profile as compared to the control group, statistically significant differences have not been found. The different treatments did not show a clear evidence of reduction of larvae burden in the infected tissues. The level of infection in the brain was higher than in the other organs examined, except for the group treated with the infusion of C. ambrosioides. The in vitro and in vivo results call for further studies on these natural products, in order to find alternative therapeutic regimens for human toxocariasis.
Descrição
Palavras-chave
Biologia molecular Helmintíases Toxocara canis Terapêutica Medicina tradicional
Contexto Educativo
Citação
Editora
Instituto de Higiene e Medicina Tropical