In vitro and in vivo action of terpinen-4-ol, γ-terpinene, and α-terpinene against Trypanosoma evansi

•In vitro, a trypanocidal effect compounds was observed when used alone or associated.•In vitro, the α-terpinene showed faster trypanocidal effect compared to chemotherapy.•α-terpinene was able to extend animal longevity, but showed no curative efficacy.•Chemotherapy associate with α-terpinene showed a curative efficacy of 57.14%.•α-terpinene from M. alternifolia is the one responsible for the trypanocidal effect.

This study aimed to evaluate the susceptibility in vitro and in vivo of Trypanosoma evansi to terpinen-4-ol, γ-terpinene and α-terpinene, the three main compounds of tea tree oil (Melaleuca alternifolia) with known efficacy in the treatment of trypanosomosis. In vitro, a trypanocidal effect of terpinen-4-ol, γ-terpinene, and α-terpinene was observed when used alone or associated at 0.5, 1 and 2% concentrations i.e., the α-terpinene showed a faster trypanocidal effect when compared to chemotherapy (diminazene aceturate - D.A.). In vivo studies were performed in two experiments: I and II where experiment I used T. evansi infected mice treated with terpinen-4-ol, γ-terpinene and α-terpinene alone (at a dose of 1.0 mL kg−1) or associated (two compounds, dose of 0.5 mL kg−1 of each compound; tree compounds, dose of 0.335 mL kg−1 of each compound); Treatment with α-terpinene was able to extend animal longevity, but showed no curative efficacy. In experiment II, T. evansi infected mice were treated with D.A. associate with α-terpinene, where a curative efficacy of 57.14% was found, a much better result when D.A. was used alone (14.28%). In summary, α-terpinene associated with D.A. can be used as an alternative treatment for T. evansi infection. The compound α-terpinene from M. alternifolia essential oil is the one responsible for the trypanocidal effect, a fact confirmed by in vitro results and the increased longevity observed on treated mice.

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