Efeito da infusão de Artemisia annua cultivada em solo com aplicação de silicato de cálcio e magnésio sobre o controle de Toxoplasma gondii in vitro

Abstract

Toxoplasmosis is an important zoonotic disease due to ability of its causal agent, Toxoplasma gondii, to infect large number of vertebrates and to be associated with congenital infection or opportunistic disease in immunosuppressed patients. As the traditional treatment has shown adverse effects, low-toxicity compounds including artemisinin and its derivatives have been researched, as well Artemisina annua tea infusion. The use of silicon in the soil of A. annua crops and its role on artemisinin content has not been studied yet. This study aimed to investigate the effects of silicon on A. annua plant physiology and the role of the tea infusion obtained from these plants in the control of T. gondii infection in cell culture. The experimental design was a completely randomized design (CRD), in which A. annua was planted in the soil with five different doses of calcium/magnesium silicate (0, 200, 400, 800 and 1600 kg ha-1) and five replications, and maintained in a greenhouse. Analysis of foliar macronutrients showed a significant increase only for nitrogen, in the presence of the highest dose of silicate in the soil. The foliar micronutrient and Si concentrations as well the plant height were not significantly changed with any silicate doses in the soil. The use of 400 kg ha-1 of silicate induced the highest total glandular trichome area that was also associated with the intact glandular trichomes, as observed by scanning electron microscopy, and with the highest artemisinin content in plant leaves and tea infusion, as determined by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC), respectively. HeLa cell treatments along with or after T. gondii infection, with infusion of A. annua grown in the soil without or with silicate (400 kg ha-1), induced a decrease of parasite proliferation in a dose-dependent manner, as also seen for cell treatment with pure artemisinin. In conclusion, the use of silicon had positive effect on the glandular trichome areas and artemisinin contents, but this outcome was not associated with a better efficacy of A. annua tea infusion on T. gondii replication. These findings suggest that other components rather than artemisinin could be contributing to this effect, such as flavonoids present in its leaves, which may act in synergism with the artemisinin and improve its efficacy.