Chemical Composition of Leaf Essential Oils of Four Cinnamomum Species and Their Larvicidal Activity Against Anophelus sinensis (Diptera: Culicidae)

Abstract

Essential oils from Cinnamomum camphora, Cinnamomum japonicum, Cinnamomum szechuanense and Cinnamomum subavenium were investigated for their chemical compositions and larvicidal activities against Anopheles sinensis larvae. The results showed that a total of 51 chemical compounds were identified from the four essential oils. The major ingredients of C. subavenium essential oil were engenol (67.73%) and engenol acetate (13.19%), while C. szechuanense, C. camphora and C. japonicum was 1,8-cineole, accounting for 42.90%, 40.91% and 24.62% in total oil, respectively. More importantly, engenol and engenol acetate were only detected from C. subavenium essential oils, suggesting that the chemical composition of C. subavenium essential oil was quite different from those of C. camphora, C. szechuanense and C. japonicum. Cluster analysis also confirmed the significant difference between C. subavenium and the other three essential oils. The four essential oils all acted against A. sinensis larvae in a dose-dependent manner. Among them, C. subavenium essential oils have the strongest larvicidal activity with the lethal concentration 50 (LC50) of 79.63 μg/mL, while the LC50 of other essential oils were 96.81 μg/mL (C. szechuanense), 109.40 μg/mL (C. camphora) and 117.80 μg/mL (C. japonicum), respectively. Comparative analysis of the chemical compositions and the larvicidal activities of the essential oils showed that the higher larvicidal activity of C. subavenium essential oil was probably due to its high eugenol and engenol acetate content. These oils, especially C. subavenium essential oil, should be promising alternatives to existing larvicides, or could be integrated into larval source management compounds for A. sinensis control.