Chemical constituents and biological activities against Tribolium castaneum (Herbst) of the essential oil from Citrus wilsonii leaves

The essential oil obtained from Citrus wilsonii Tanaka leaves with hydrodistillation was investigated by GC and GC-MS. The main components of the essential oil were identified to be citronellol (16.94%), nerol acetate (10.35%), γ-terpinen (9.85%), citronellal (9.36%) and β-pinene (6.72%). Among them, the four active constituents, predicted with a bioactivity-test, were isolated and identified as citronellol, γ-terpinene, nerol (neryl) acetate and β-pinene. It was found that the essential oil of C. wilsonii leaves and isolated compounds possessed fumigant and contact toxicity against Tribolium castaneum adults. The essential oil and γ-terpinen showed strong fumigant toxicity against T. castaneum (LC50 = 8.18 and 4.09 mg L-1). Repellency of the crude oil and active compounds was also determined. Citronellol, neryl acetate and β-pinene were strongly repellent (100%, 86% and 92%, respectively, at 78.63 nL cm-2, after 2 h treatment) against T. castaneum. The essential oil and citronellol exhibited the same level of repellency compared with the positive control, DEET. The results indicate that the essential oil of C. wilsonii leaves and its active compounds had the potential to be developed as natural fumigants, insecticides and repellents for control of T. castaneum