Chemical composition and biological activity against Tribolium castaneum (Coleoptera: Tenebrionidae) of Artemisia brachyloba essential oil

The aim of this study was to investigate the biological effects of essential oil from Artemisia brachyloba against Tribolium castaneum. The essential oil from the aerial parts of Artemisia brachyloba was obtained by hydro-distillation and analyzed by gas chromatography-mass spectrometry. The toxicity and repellency of the oil and its two major compounds were evaluated against Tribolium castaneum. The essential oil is rich in oxygenated monoterpenes (55.52%) and oxygenated sesquiterpenoids (16.47%); its major components are alpha-terpineol (21.74%) and davanone (10.67%). The LD50 values of the oil, alpha-terpineol, and davanone topically applied were 22.55-31.84, 17.09-29.16, and 43-56 mu g/mg insect, respectively. The LD50 value of filter papers treated with the oil and alpha-terpineol was 15.29-23.74 mu L/cm(2), whereas that of filter papers treated with davanone was 66.3-256.57 mu L/cm(2). Fumigation with the oil, alpha-terpineol, and davanone had LD50 values of 13.75-22.26, 9.98-20.17, and 68.53-124.41 mu L/L air, respectively. The repellent property of essential oil was 73.33%-96.67%, while the repellent property of alpha-terpineol of 0.315 mu L/cm 2 was 75.00%-100%. Moderate repellency (46.67%-61.67%) was achieved by 0.315 mu L/cm(2) davanone. Biochemical assays have revealed multiple mechanisms of A. brachyloba essential oil in regulating enzymatic activities, thereby reducing the overall tested enzyme activities of adults of T. castaneum even at high concentrations or during long exposure time. Furthermore, the biological activity of alpha-terpinol was similar to that of the oil, while davanone was quite different. The toxicity of A. brachyloba essential oils may be dependent on the cumulative or synergistic relationship between several phytochemical groups.