The screening of Chinese medicinal herbs for insecticidal principles showed that the essential oil of Echinops grijsii Hance roots possessed significant larvicidal activity against mosquitoes. The essential oil was extracted via hydrodistillation and its constituents were determined by gas chromatography-mass spectrometry (GC-MS) analysis. GC-MS analyses revealed the presence of 31 components, with 5-(3-buten-1-yn-1-yl)-2,2′-bithiophene (5-BBT, 27.63%), α-terthienyl (α-T, 14.95%), 1,8-cineole (5.56%) and cis-β-ocimene (5.01%) being the four major constituents. Based bioactivity-directed chromatographic separation of the essential oil led to the isolation of 5-BBT, 5-(4-isovaleroyloxybut-1-ynyl)-2,2′-bithiophene (5-IBT) and α-T as active compounds. The essential oil of E. grijsii exhibited larvicidal activity against the fourth instar larvae of Aedes albopictus, Anopheles sinensis and Culex pipiens pallens with LC50 values of 2.65 μg/mL, 3.43 μg/mL and 1.47 μg/mL, respectively. The isolated thiophenes, 5-BBT and 5-IBT, possessed strong larvicidal activity against the fourth instar larvae of Ae. albopictus (LC50 = 0.34 μg/mL and 0.45 μg/mL, respectively) and An. sinensis (LC50 = 1.36 μg/mL and 5.36 μg/mL, respectively). The two isolated thiophenes also had LC50 values against the fourth instar larvae of C. pipiens pallens of 0.12 μg/mL and 0.33 μg/mL, respectively. The findings indicated that the essential oil of E. grijsii roots and the isolated thiophenes have an excellent potential for use in the control of Ae. albopictus, An. sinensis and C. pipiens pallens larvae and could be used in the search for new, safer and more effective natural compounds as larvicides.
Water-distilled essential oil from Elsholtzia ciliate (Labiatae)a erial parts at flowering stage was analyzed by gas chromatography/mass spectrometry (GC/MS). Thirty-six compounds,a ccountingf or 98.3% of the total oil content, were identified, and the main components of the essential oil were dehydroelsholtzia ketone (26.5%),(R)-carvone (16.6%),elsholtzia ketone( 14.6%),a nd d-limonene (4.1%).T he essential oil contained highera mounts of monoterpenoids (83.4%) than of sesquiternoids (8.3%).Bioactivity-directed chromatographic separation of the essential oil on repeatedsilica gel columns led to the isolation of three monoterpenoids.T he essential oil possessed fumigant toxicity against the booklice (Liposcelis bostrychophila)w ith an LC 50 value of 475.2 mg/l, while the isolatedc onstituents,( R)-carvone,d ehydroelsholtzia ketone, and elsholtzia ketoneh ad LC 50 valueso f4 17.4, 658.2, and 547.3 mg/l, respectively.T he essential oil also exhibitedc ontact toxicity against L. bostrychophila with an LC 50 value of 145.5 mg/cm 2 .( R)-Carvone, dehydroelsholtzia ketone,a nd elsholtzia ketone exhibited acute toxicity against the booklice with LC 50 valuesof5 7. 0, 151.5, and 194.1 mg/cm 2 ,respectively.The results indicated that the essential oil and the isolated constituentshave potential for the development into natural insecticides/fumigants for the controlo fi nsects in stored grains.
Watermelon diseases caused by pathogenic bacteria were endemic in Liaoning and Jilin Provinces from 2019 to 2020 in China, resulting in serious economic losses to the watermelon industry. This study characterized 56 strains isolated from symptomatic watermelon leaves collected from Liaoning and Jilin Provinces. Through morphological observation, 16S rRNA and gyrB sequence analysis, and BIOLOG profiles, the pathogen was identified as Pseudomonas syringae. In China, the watermelon disease caused by P. syringae was reported for the first time. The multilocus sequence analysis showed that the isolated strains belonged to three different clades within P. syringae phylogroup 2. Interestingly, most of them (79%) belonged to clade 2a, 14% were clade 2b, and 7% were clade 2d. This indicates that bacterial leaf spot outbreaks of watermelon in China were caused by multiple sources and mainly by P. syringae clade 2a.
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