Abstract:To find a new and safe alternative to conventional insecticides, we evaluated the fumigant toxicity of eight Lamiaceae essential oils and their constituents against the adult rice weevil Sitophilus oryzae. Of the eight species tested, hyssop (Hyssopus offcinalis), majoram (Origanum majorana), and Thymus zygis essential oils showed strong fumigant toxicity against S. oryzae adults at 25 mg/L air concentration. Constituents of active essential oils were analyzed by gas chromatography coupled to flame ionization detector (FID) and gas chromatography-mass spectrometry. A total of 13, 15, and 17 compounds were identified from hyssop, majoram, and Thymus zygis essential oils, respectively. Pinocamphone and isopinocamphone were isolated by open column chromatography. Among the test compounds, pinocamphone and isopinocamphone showed the strongest fumigant toxicity against S. oryzae. Sabinene hydrate, linalool, α-terpineol, and terpinen-4-ol exhibited 100% fumigant toxicity against S. oryzae at 3.9 mg/L air concentration. The measured toxicity of the artificial blends of the constituents identified in hyssop, majoram, and Thymus zygis oils indicated that isopinocamphone, terpine-4-ol, and linalool were major contributors to the fumigant toxicity of the artificial blend, respectively.
The degree of polarization around the water pool generated in aerosol‐ OT/hexane/water reversed micelle solutions was studied by monitoring the depolarization of solubilized probe fluorescence. The 5(E)‐styryI‐1, 3‐dimethyl uracil (SDU) used in this study was moderately polar and proved to be solubilized between the interface and hydrocarbon phases in reversed micelle solution by a fluorescence quenching study with hydrophilic and hydrophobic quenchers. The degree of polarization monitored by SDU was parallel with that obtained from the fluorescence depolarization study of hydrophylic probes solubilized in the water pool and interface. A dramatic increase in microviscosity was observed when ω value became small.
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