Strong Larvicidal and Molluscicidal Activities of the (E)-β-caryophyllene-rich Chemotype ofCallicarpa macrophyllaVah Leaf Essential Oil Growing Wild in Vietnam

Essential oils have been shown to effectively control vectors and intermediate hosts of disease transmission. The essential oil from the leaves of the Vietnamese species Callicarpa macrophylla was investigated for chemical composition, and evaluated for the pesticidal activities of both the essential oil and its major components. The essential oils were obtained by hydrodistillation (Clevenger apparatus) and analyzed by gas chromatography/mass spectrometry (GC/MS). The main components identified in the essential oil were (E)-β-caryophyllene (24.1%), caryophyllene oxide (18.7%), β-pinene (17.8%), and myrtenal (9.3%). The essential oil was screened for mosquito larvicidal activity and molluscidical activity. The essential oil showed promising potential for larval control of Aedes aegypti and Aedes albopictus with LC50 values of 34.01 and 48.45 µg/mL after 48 h of exposure, respectively. Furthermore, this essential oil demonstrated excellent molluscidical activity against Pomacea canaliculata with an LC50 value of 8.09 µg/mL. The essential oil did not exhibit toxicity to the non-target organism Diplonychus rusticus with mortality rates of only 10.0% and 11.25% after 24 h and 48 h of exposure, respectively, at a concentration of 100 μg/mL. The good acetylcholinesterase (AChE) enzyme inhibitory activity could be a mechanism responsible for the potent larvicidal activities of the essential oil. The essential oil of the leaves of Callicarpa macrophylla may be considered as an environmentally-friendly source of pesticide.