In vitro and in silico evaluation of the acaricidal activity of ethanol extract from Xylopia emarginata Mart. on Rhipicephalus microplus.

The cattle tick Rhipicephalus microplus has developed resistant populations due to the recurrent use of synthetic acaricides, increasing health and environmental risks; plant extracts may represent a promising alternative. This study evaluated the acaricidal potential of the ethanol extract (EE) from Xylopia emarginata Mart. against larvae and engorged females of R. microplus. In vitro assays, histological, chromatographic, and in silico analyses were performed. Gas chromatography coupled with mass spectrometry identified nine compounds, including myrtenal, spathulenol, and caryophyllene oxide. In bioassays, the EE showed high acaricidal activity against larvae, with CL₉₀ = 61.92 mg mL⁻¹ (95 % CI: 53.84-73.84 mg mL⁻¹). In engorged females, oviposition was not significantly affected; however, hatchability was reduced by 32.79 %, accompanied by histological alterations in the ovaries, such as cytoplasmic degradation, vacuolization, and oocyte rupture, that compromised embryonic development. Molecular docking analyses revealed strong binding affinities of spatulenol and caryophyllene oxide to key resistance-related enzymes. For all enzymes, the first score refers to spatulenol and the second to caryophyllene oxide: -8.215 and -8.374 kcal/mol for GST, -6.984 and -7.109 kcal/mol for AChE, and -7.791 and -6.702 kcal/mol for CYP450, suggesting potential mechanisms underlying their acaricidal effects. The predicted absorption, distribution, metabolism, excretion, and toxicity properties indicated good intestinal absorption and compliance with Lipinski's Rule of 5. Together, the results demonstrate that the EE of X. emarginata has promising acaricidal activity, acting at different stages of the tick life cycle and representing a sustainable alternative for the integrated control of R. microplus.