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

Abstract

Hydro distilled essential oil of the aerial parts of Caryopteris incana harvested 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 α-cadinol (8.5 %). Three active compounds (α-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 castaneum with LC50 values of 2.2, 5.6, and 0.5 mg/l, respectively. The essential oil and the three constituents, α-cadinol, myrtenol, and 4-terpineol also displayed contact toxicity against T. castaneum with LC50 values of 30.7, 123.4, 29.7, and 21.3 μg/adult, respectively. The study indicates that the essential oil of C. incana and its isolated constituents have the potential to be developed to natural insecticides for the control of grain storage insects.