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.
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Yang, K.; Zhou, Y.X.; Wang, C.F.; Du, S.S.; Deng, Z.W.; Liu, Q.Z.; Liu, Z.L. Toxicity of Rhododendron anthopogonoides Essential Oil and Its Constituent Compounds towards Sitophilus zeamais. Molecules 2011, 16, 7320-7330.
Yang K, Zhou YX, Wang CF, Du SS, Deng ZW, Liu QZ, Liu ZL. Toxicity of Rhododendron anthopogonoides Essential Oil and Its Constituent Compounds towards Sitophilus zeamais. Molecules. 2011; 16(9):7320-7330.
Yang, Kai; Zhou, Yu Xin; Wang, Cheng Fang; Du, Shu Shan; Deng, Zhi Wei; Liu, Qi Zhi; Liu, Zhi Long. 2011. "Toxicity of Rhododendron anthopogonoides Essential Oil and Its Constituent Compounds towards Sitophilus zeamais." Molecules 16, no. 9: 7320-7330.