RESUMEN
The aim of this study was to investigate the chemical composition and acaricidal effect of two Psidium species essential oils and selected compounds on Tetranychus urticae. Essential oils from the leaves of Psidium laruotteanum and Psidium myrsinites were obtained through hydrodistillation, analyzed using CG-FID and CG-MS and evaluated for toxicity to T. urticae by fumigation and residual contact. The susceptibility of T. urticae to monoterpenes and sesquiterpenes was also investigated. The major constituents of the P. laruotteanum oil were (E)-nerolidol (9.6 ± 0.4%) and γ-terpinene (9.4 ± 0.6%) and the major constituents of the P. myrsinites oil were ß-caryophyllene (21.2 ± 0.9%) and α-humulene (10.3 ± 0.5%). Based on the LC50 estimates, no significant differences were found between the two oils regarding toxicity by fumigation or residual contact. ß-Caryophyllene and (E)-nerolidol had the highest level of toxicity, independently of the method investigated. The findings indicate that both oils and selected constituents, especially ß-caryophyllene and (E)-nerolidol, are promising as natural acaricidal agents that affect T. urticae through more than one mode of action.
Los aceites esenciales de las hojas de Psidium laruotteanum y Psidium myrsinites se obtuvieron por hidrodestilación, se analizaron por CG-FID y CG-MS, y se evaluaron sus toxicidades por fumigación y contacto residual contra Tetranychus urticae. Se investigó también la susceptibilidad del T. urticae a monoterpenos y sesquiterpenos. En el aceite esencial de P. laruotteanum, (E)-nerolidol (9.6 ± 0.4%) y γ-terpinene (9.4 ± 0.6%) se identificaron como constituyentes mayoritarios, mientras que en el aceite esencial de P. myrsinites, ß-caryophyllene (21.2 ± 0.9%) y α-humulene (10.3 ± 0.5%) se encontraron como mayoritarios. Con base en las CL50 estimadas, no se observaron diferencias significativas entre las toxicidades de los aceites por fumigación, y tampoco por contacto residual. ßCaryophyllene y (E)-nerolidol presentaron las mayores toxicidades, independientemente del método investigado. Estos resultados indican, que los dos aceites, así como los constituyentes seleccionados, entre los que se destacan ß-caryophyllene y (E)-nerolidol, son promisores agentes acaricidas naturales por actuar en el T. urticae por más de un mecanismo de acción.
Asunto(s)
Animales , Aceites Volátiles/farmacología , Hojas de la Planta/química , Tetranychidae/efectos de los fármacos , Psidium/química , Acaricidas/farmacología , Terpenos/análisis , Brasil , Aceites Volátiles/química , Control de Plagas , Fumigación , Acaricidas/química , Ionización de Llama , Cromatografía de Gases y Espectrometría de MasasRESUMEN
ABSTRACT Essential oils from the leaves of two species of the genus Ocotea that occur in the Atlantic Forest in the state of Pernambuco, Brazil, were analyzed using gas chromatography-mass spectrometry. The acaricidal activity of these oils as well as 11 selected components and blends were evaluated in fumigation and residual contact tests against the two-spotted spider mite (Tetranychus urticae). Sixty-seven constituents were identified, totaling 97.3 ± 0.3% and 97.8 ± 0.5% of the oils from O. duckei and O. glomerata, respectively. Sesquiterpene was the dominant class. The compounds β-caryophyllene (18.6 ± 0.1%) and aromadendrene (17.3 ± 0.6%) were the main constituents of the oils from O. duckei and O. glomerata, respectively. Acaricidal action varied depending on the method employed, species and chemical nature of the selected constituents. The mites were susceptible to the oils and chemical constituents using the fumigation method. The O. duckei oil was respectively 2.5-fold and 1.5-fold more toxic than the O. glomerata oil using the fumigation and residual contact methods. Among the selected constituents, β-caryophyllene was the most toxic, independently of the method employed. The individual toxicity of the selected compounds and their blends as well as the role of these constituents in the overall toxicity of the essential oils are also discussed.