title: Toxicity of Rhododendron anthopogonoides essential oil and its constituent compounds towards Sitophilus zeamais.
abstract: The screening of several Chinese medicinal plants for insecticidal principles showed that essential oil of Rhododendron anthopogonoides flowering aerial parts possessed significant toxicity against maize weevils, Sitophilus zeamais. A total of 37 components were identified in the essential oil and the main constituents of the essential oil were 4-phenyl-2-butanone (27.22%), nerolidol (8.08%), 1,4-cineole (7.85%), caryophyllene (7.63%) and γ-elemene (6.10%), followed by α-farnesene (4.40%) and spathulenol (4.19%). Repeated bioactivity-directed chromatographic separation on silica gel columns led us to isolate three compounds, namely 4-phenyl-2-butanone, 1,4-cineole, and nerolidol. 4-Phenyl-2-butanone shows pronounced contact toxicity against S. zeamais (LD₅₀ = 6.98 mg/adult) and was more toxic than either 1,4-cineole or nerolidol (LD₅₀ = 50.86 mg/adult and 29.30 mg/adult, respectively) against the maize weevils, while the crude essential oil had a LD₅₀ value of 11.67 mg/adult. 4-Phenyl-2-butanone and 1,4-cineole also possessed strong fumigant toxicity against the adults of S. zeamais (LC₅₀ = 3.80 mg/L and 21.43 mg/L) while the crude essential oil had a LC₅₀ value of 9.66 mg/L.
authors.affiliation: Department of Entomology, China Agricultural University, Haidian District, Beijing 100193, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Yang
authors.forename: Yu Xin
authors.initials: YX
authors.lastname: Zhou
authors.forename: Cheng Fang
authors.initials: CF
authors.lastname: Wang
authors.forename: Shu Shan
authors.initials: SS
authors.lastname: Du
authors.forename: Zhi Wei
authors.initials: ZW
authors.lastname: Deng
authors.forename: Qi Zhi
authors.initials: QZ
authors.lastname: Liu
authors.forename: Zhi Long
authors.initials: ZL
authors.lastname: Liu
mesh_terms: D000818:Animals; D002090:Butyrophenones / Q000494:pharmacology; D001517:Coleoptera / Q000187:drug effects*; D000081005:Cyclohexane Monoterpenes; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000494:pharmacology; D007306:Insecticides / Q000032:analysis / Q000737:chemistry / Q000633:toxicity; D039821:Monoterpenes / Q000494:pharmacology; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology / Q000633:toxicity*; D010938:Plant Oils / Q000737:chemistry / Q000494:pharmacology / Q000633:toxicity*; D029793:Rhododendron / Q000737:chemistry* / Q000633:toxicity; D012717:Sesquiterpenes / Q000494:pharmacology
chemical_list: D002090:Butyrophenones; D000081005:Cyclohexane Monoterpenes; D004365:Drugs, Chinese Herbal; D007306:Insecticides; D039821:Monoterpenes; D009822:Oils, Volatile; D010938:Plant Oils; D012717:Sesquiterpenes; C058951:1,4-cineole; C037055:nerolidol