Chemical composition, mosquito larvicidal and molluscicidal activities of Magnolia foveolata leaf essential oil

Viral disease-causing pathogens transmitted by mosquito vectors are a global health problem, causing economic burden in many underdeveloped countries. Searching for pesticides from plant sources that are readily available in areas with mosquito-borne diseases to control mosquitoes may be an economical and timely solution to prevent and respond to pandemic outbreaks. Magnolia essential oils have shown a myriad of biological activities and we hypothesize that Magnolia foveolata essential oil may show pesticidal activities. The purpose of this investigation, therefore, was to characterize the essential oil of M. foveolata and to screen the essential oil for mosquito larvicidal and molluscicidal activities. Essential oil from the leaves of M. foveolata was obtained by hydrodistillation using a Clevenger type apparatus for 5 h. Chemical composition was analyzed by gas chromatography–mass spectrometry (GC-MS), gas chromatography with flame ionization detection (GC-FID), chiral gas chromatography - mass spectrometry. Pesticide activities of the essential oil were tested following WHO guidelines with modifications. The leaf essential oil of M. foveolata was dominated by the monoterpene hydrocarbons (+)-α-thujene (22.5%), (+)-α-pinene (6.9%) and (−)-α-pinene (9.0%), and p-cymene (9.5%), as well as the oxygenated monoterpenoid (−)-terpinen-4-ol (9.7%). The M. foveolata leaf essential oil was very active against the larvae of four mosquitoes Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, Culex fuscocephala with 24-h LC50 less than 40 μg/mL. The leaf essential oil of M. foveolata was also active against the fresh water snails, Pomacea canaliculata and Gyraulus convexiusculus, with LC90 values of 10.5 μg/mL and 23.6 μg/mL, respectively. Unfortunately, this essential oil also showed strong toxicity against non-target organisms Diplonychus rusticus, Anisops sp., Oreochromis sp., and Fejervarya limnocharis tadpoles. With appropriate care, the essential oil of M. foveolata may be considered as a pesticide applied to control mosquito species such as Ae. aegypti or Cx. quinquefasciatus living in urban areas.