Atividade acaricida do eugenol, do óleo essencial e do hidrolato de Syzygium aromaticum (Myrtaceae) frente a espécie Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Abstract

Ticks are important vectors of diseases in animals and humans. The cattle tick Rhipicephalus (Boophilus) microplus (Canestrini, 1887) has caused serious harm to livestock raising in Brazil, considering the costs of controlling it, revenue loss as a result of a smaller production of milk and meat, and leather damage, in addition to transmitting diseases. The use of medicinal plants and their derivatives with acaricide action is considered an alternative against the formation of chemicals resistance. Due to the need for more efficient alternatives with less environmental impact, this study aims to evaluate the acaricide action in vitro of eugenol, essential oil and hydrolate of Syzygium aromaticum (clove). Additionally, it has also investigated the acaricide activity of the essential oil and eugenol when incorporated into a formulation. The extraction of the essential oil and hydrolate was performed by steam distillation of dried flower buds of the plant. The chemical characterization of clove essential oil by GC/MS revealed the presence of the major components eugenol (83.97%), caryophyllene (3.04%), humulene (0.42%), and eugenol acetate (12.58%). The ticks from different geographical areas were treated with the test compounds in different stages of the tick cycle. In the larval packet test, mortality was assessed at concentrations of eugenol, essential oil and hydrolate ranging from 0.1 to 2.0%. The eggs production levels, the larvae hatching, and their efficiency on ticks were assessed using the adult immersion test, in which eugenol and essential oil were used at concentrations of 1.25 to 10%. The eugenol and the essential oil caused 100% mortality of larvae, starting at 0.25 and 0.5%, respectively. The test with hydrolate showed no activity at the concentrations tested. In the adult immersion test, the eugenol and the essential oil showed results greater than 95% efficacy at concentrations of 5.0%, completely inhibiting the larvae hatching at 10%. The use of eugenol, purified substance (99-100%), gave no significant superiority in efficacy of treatment with the clove essential oil, which strengthens the potential use of clove essential as an acaricide, being it a low cost and accessible alternative, with high yield in the extraction process. The formulation developed did not promote better efficacies of treatment when compared to ethanol solutions, which suggests that further research should be conducted from the perspective of testing the essential oil of cloves in other formulations that can improve their activity. Furthermore, in vivo tests are recommended for an active efficiency in field conditions validation.