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The aim of this research was to determine larvicidal activity of the ethanol extract of Inula racemosa Hook. f. (Compositae) roots against the larvae of the Culicidae mosquito Aedes albopictus and to isolate any larvicidal constituents from the extract. Based on bioactivity-guided fractionation, 11,13-dihydroisoalantolactone (1), macrophyllilactone E (2), 5α-epoxyalantolactone (3), and epoxyisoalantolactone (4) were isolated and identified as the active constituents. Compounds 1 and 2 exhibited strong larvicidal activity against the early fourth-instar larvae of A. albopictus with LC50 values of 21.86 µg/mL and 18.65 µg/mL, respectively, while the ethanol extract had a LC50 value of 25.23 µg/mL. Compounds 3 and 4 also possessed larvicidal activity against the Asian tiger mosquitoes with LC50 values of 29.37 µg/mL and 35.13 µg/mL, respectively. The results indicated that the ethanol extract of I. racemosa and the four isolated constituents have potential for use in the control of A. albopictus larvae and could be useful in the search of newer, safer, and more effective natural compounds as larvicides. [ABSTRACT FROM AUTHOR]

During our screening program for agrochemicals from Chinese medicinal herbs and wild plants, the essential oil of Cinnamomum camphora leaves was found to possess strong fumigant and contact toxicity against Lasioderma serricorne adults with LC50/LD50 values of 2.5 mg/L air and 21.25 µg/adult, respectively. The essential oil obtained by hydrodistillation was investigated by GC and GC-MS. The main components of the essential oil were identified to be D-camphor (40.54%), linalool (22.92%), cineole (11.26%), and 3,7,11-trimethyl-3-hydroxy-6,10-dodecadien-1-yl acetate (4.50%). Bioactivity-directed chromatographic separation on repeated silica gel columns led to the isolation of D-camphor and linalool. D-camphor and linalool showed strong fumigant toxicity (LC50 = 2.36 and 18.04 mg/L air, resp.) and contact toxicity (LD50 = 13.44 and 12.74 µg/adult, resp.) against L. serricorne. The results indicate that the essential oil of C. camphora and its active compounds had the potential to be developed as natural fumigants and insecticides for control of L. serricorne. [ABSTRACT FROM AUTHOR]