Acaricidal activity and chemical composition of the essential oil from three Piper species.

The chemical composition of the essential oil obtained by hydrodistillation of the aerial parts of Piper amalago, Piper mikanianum, and Piper xylosteoides was elucidated by gas chromatography (GC) and GC/mass spectrometry analyses. P. mikanianum and P. xylosteoides essential oils presented phenylpropanoids as their main compounds (67.89% and 48.53%, respectively) whereas P. amalago was rich in monoterpene and sesquiterpene hydrocarbons (84.95%). The essential oils obtained were investigated for their effect on newly hatched larvae of the cattle tick, Rhipicephalus (Boophilus) microplus. The essential oil of P. mikanianum (LC(50) 2.33 microL/mL) was more active than that of P. xylosteoides (LC(50) 6.15 microL/mL) against the larvae, while the oil of P. amalago was inactive. These results suggest that phenylpropanoids, mainly apiol and safrole, are responsible for the acaricidal activity.