Chemical Composition and Insecticidal Activities of the Essential Oil fromCaryopteris incana(Thunb. ex Hout.) Miq. Aerial Parts

Hydro distilled essential oil of the aerial parts ofCaryopteris incanaharvested from Zhejiang province, China was analyzed by gas chromatography-mass spectrometry (GC/MS). Thirty-nine components were identified and the principal compounds in the essential oil were 4-terpineol (13.5 %), 1-octen-3-ol (12.3 %), myrtenol (8.8 %), and alpha-cadinol (8.5 %). Three active compounds (alpha-cadinol, myrtenol, 4-terpineol) were isolated and identified from the essential oil based on bioactivity-directed fractionation. The essential oil and its isolates, myrtenol and 4-terpineol exhibited fumigant activity against the red flour beetles,Tribolium castaneumwith LC(50)values of 2.2, 5.6, and 0.5 mg/l, respectively. The essential oil and the three constituents, alpha-cadinol, myrtenol, and 4-terpineol also displayed contact toxicity againstT. castaneumwith LC(50)values of 30.7, 123.4, 29.7, and 21.3 mu g/adult, respectively. The study indicates that the essential oil ofC. incanaand its isolated constituents have the potential to be developed to natural insecticides for the control of grain storage insects.