Qi Zhi Liu

Repellent Constituents of Essential Oil of Cymbopogon distans Aerial Parts against Two Stored-Product Insects

The screening for bioactive principles from several Chinese medicinal herbs showed that the essential oil of Cymbopogon distans aerial parts possessed strong repellency against the booklouse, Liposcelis bostrychophila , and the red flour beetle, Tribolium castaneum . A total of 36 components of the essential oil were identified by GC and GC-MS. trans-Geraniol (16.54%), (R)-citronellal (15.44%), (+)-citronellol (11.51%), and α-elemol (9.06%) were the main components of the essential oil followed by β-eudesmol (5.71%) and (+)-limonene (5.05%). From the essential oil, four monoterpenes were isolated by bioassay-guided fractionation. The compounds were identified as limonene, citronellol, citronellal, and trans-geraniol. Geraniol and citronellol were strongly repellent against the booklouse, L. bostrychophila, whereas citronellal and limonene exhibited weak repellency against the booklouse. Geraniol and citronellol exhibited comparable repellency against the booklouse relative to the positive control, DEET. Moreover, geraniol and citronellol exhibited stronger repellency against the red flour beetle than DEET, whereas the two other compounds showed the same level of repellency against the red flour beetle compared with DEET.

Nematocidal Flavone-C-Glycosides against the Root-Knot Nematode (Meloidogyne incognita) from Arisaema erubescens Tubers

A screening of several Chinese medicinal herbs for nematicidal properties showed that Arisaema erubescens (Wall.) Schott tubers possessed significant nematicidal activity against the root-knot nematode (Meloidogyne incognita). From the ethanol extract, two nematicidal flavone-C-glycosides were isolated by bioassay-guided fractionation. The compounds were identified as schaftoside and isoschaftoside on the basis of their phytochemical and spectral data. Schaftoside and isoschaftoside possessed strong nematicidal activity against M. incognita (LC50 = 114.66 μg/mL and 323.09 μg/mL, respectively) while the crude extract of A. erubescens exhibited nematicidal activity against the root-knot nematode with a LC50 value of 258.11 μg/mL.

Toxicity of Rhododendron anthopogonoides essential oil and its constituent compounds towards Sitophilus zeamais.

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 μg/adult) and was more toxic than either 1,4-cineole or nerolidol (LD50 = 50.86 μg/adult and 29.30 μg/adult, respectively) against the maize weevils, while the crude essential oil had a LD50 value of 11.67 μg/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.

Chemical Composition and Nematicidal Activity of Essential Oil of Agastache rugosa against Meloidogyne incognita

The aim of this research was to determine the chemical composition and nematicidal activity of essential oil of Agastache rugosa flowering aerial parts against the root knot nematode, Meloidogyne incognita, and to isolate and identify any nematicidal constituents from the essential oil. The essential oil of A. rugosa aerial parts was obtained by hydrodistillation and analyzed by GC-FID and GC-MS. A total of 37 components of the essential oil were identified, with the principal compounds being methyleugenol (50.51%), estragole (8.55%), and eugenol (7.54%), followed by thymol (3.62%), pulegone (2.56%), limonene (2.49%) and caryophyllene (2.38%). Based on bioactivity-guided fractionation, the three active constituents were isolated from the essential oil and identified as methyleugenol, estragole and eugenol. The essential oil of A. rugosa exhibited strong nematicidal activity against M. incognita, with a LC50 value of 47.3 μg/mL. The components eugenol (LC50 = 66.6 μg/mL) and methyleugenol (LC50 = 89.4 μg/mL) exhibited stronger nematicidal activity against M. incognita (LC50 = 185.9 μg/mL). The results indicate that the essential oil of A. rugosa aerial parts and its constituent compounds have potential for development into natural nematicides for control of the root knot nematode.

Feeding Deterrents against Two Grain Storage Insects from Euphorbia fischeriana

The screening of several Chinese medicinal herbs for insecticidal principles showed that Euphorbia fischeriana roots possessed significant feeding deterrent activity against two stored-product insects (Tribolium castaneum and Sitophilus zeamais). From ethanol extract, four feeding deterrents were isolated by bioassay-guided fractionation. The compounds were identified as jolkinolide B, 12-deoxyphorbol 13-(9Z)-octadecenoate 20-acetate, 17-hydroxyjolkinolide A and B on the basis of their phytochemical and spectral data. Jolkinolide B and 17-hydroxyjolkinolide B possessed strong feeding deterrent activities against S. zeamais (EC50 = 342.1 and 543.9 ppm, respectively) and T. castaneum adults (EC50 = 361.4 and 551.5 ppm, respectively). 17-Hydroxyjolkinolide A and 12-deoxyphorbol 13-(9Z)-octadecenoate 20-acetate A also exhibited feeding deterrent activity against the two grain storage insects with EC50 values of 631.9 and 884.3 ppm for S. zeamais and 656.5 and 1058.4 ppm for T. castaneum adults.

Antifeedant Diterpenoids against Tribolium castaneum from the Stems and Twigs of Ceriops tagal (Rhizophoraceae)

The screening of several Chinese mangrove plants for insecticidal principles showed that ethanol extract of Ceriops tagal stems and twigs possessed significant feeding deterrent activity against the red flour beetle, Tribolium castaneum (Family: Rhizophoraceae). From the ethanol extract, three feeding deterrent diterpenoids were isolated by bioassay-guided fractionation. The compounds were identified as tagalsin A, B, and H on the basis of their phytochemical and spectral data. Tagalsin A, B, and H exhibited strong feeding deterrent activity against T. castaneum adults with EC50 values of 375.3 ppm, 277.3 ppm, and 285.45 ppm, respectively.

A new eudesmane sesquiterpene glucoside from Liriope muscari fibrous roots.

The screening of several Chinese medicinal herbs for nematocidal properties showed that the ethanol extract of Liriope muscari fibrous roots possessed significant nematocidal activity against the pine wood nematode (Bursaphelenchus xylophilus). From the ethanol extract, a new constituent (1,4-epoxy-cis-eudesm-6-O-β-D-glucopyranoside) and three known glycosides [1β,6α-dihydroxy-cis-eudesm-3-ene-6-O-β-D-glucopyranoside (liriopeoside A), 1β,6β-dihydroxy-cis-eudesm-3-ene-6-O-β-D-glucopyranoside, and 1α,6β-dihydroxy-5,10-bis-epi-eudesm-4(15)-ene-6-O-β-D-glucopyranoside] were isolated by bioassay-guided fractionation. The structures were elucidated by 1D and 2D NMR and MS techniques. 1,4-Epoxy-cis-eudesm-6-O-β-D-glucopyranoside possessed moderate nemato-cidal activity against B. xylophilus with a LC50 value of 339.76 μg/mL, while liriopeoside A (LC50 = 82.84 μg/mL) and 1β,6β-dihydroxy-cis-eudesm-3-ene-6-O-β-D-glucopyranoside (LC50 = 153.39 μg/mL) also exhibited nematocidal activity against B. xylophilus. The crude extract of L. muscari fibrous roots exhibited nematocidal activity against the pine wood nematode with a LC50 value of 182.56 μg/mL.

Chemical composition and toxicity of the essential oil of Cayratia japonica against two grain storage insects

During our screening program for new agrochemicals from Chinese medicinal herbs, essential oil of Cayratia japonica aerial parts was found to possess strong insecticidal activities against Sitophilus zeamais and Tribolium castaneum. A total of 37 components of the essential oil were identified by gas chromatography (GC) and GC–mass spectrometry (GC–MS). Linalool (19.4%), trans-α-ionene (11.4%), α-terpineol (7.9%), dihydroactinolide (7.8%) and geranial (5.8%) were the main components of the essential oil. The essential oil exhibited strong fumigant toxicity against S. zeamais and T. castaneum adults with LC50 values of 10.05 and 15.67 mg/L air, respectively. Cayratia japonica essential oil also possessed contact toxicity against S. zeamais and T. castaneum adults with LD50 values of 32.06 and 44.49 mg/adult, respectively. The essential oil C. japonica may have potential to be developed as a new natural fumigant/insecticide for the control of stored-product insects.

Analysis of the essential oil of Dipsacus japonicus flowering aerial parts and its insecticidal activity against Sitophilus zeamais and Tribolium castaneum.

Water-distilled essential oil from the aerial parts of Dipsacus japonicus Miq. (Dipsacaceae) at the flowering stage was analysed by gas chromatography-mass spectrometry (GC-MS). Forty-six compounds, accounting for 96.76% of the total oil, were identified and the main compounds of the essential oil were linalool (11.78%), trans-geraniol (8.58%), 1,8-cineole (7.91%), β-caryophyllene (5.58%), α-terpineol (5.32%), β-selinene (5.15%), and spathulenol (5.04%). The essential oil of D. japonicus possessed contact toxicity against two grain storage insects, Sitophilus zeamais and Tribolium castaneum adults, with LD50 values of 18.32 μg/ adult and 13.45 μg/adult, respectively. The essential oil of D. japonicus also exhibited pronounced fumigant toxicity against S. zeamais (LC50 = 10.11 mg/l air) and T. castaneum adults (LC50 = 5.26 mg/l air). Of the three major compounds, 1,8-cineole exhibited stronger fumigant toxicity than the crude essential oil against S. zeamais and T. castaneum adults with LC50 values of 2.96 mg/l air and 4.86 mg/l air, respectively

Nematocidal Constituents from the Ethanol Extract of Evodia rutaecarpa Hort Unripe Fruits

The ethanol extract of Chinese medicinal herb, Evodia rutaecarpa Hort unripe fruits, was found to possess nematocidal activity against the root-knot nematodes, Meloidogyne incognita, during the screening program for new agrochemicals from local wild plants and Chinese medicinal herbs. Bioactivity-guided chromatographic separation of the ethanol extract of E. rutaecarpa on repeated silica gel columns led to isolate five constituent components (two limonoids, evodol and limonin; three alkaloids, evodiamine, rutaecarpine, and wuchuyuamide I). Evodiamine ( L C 5 0 = 7 3 . 5 5 μg/mL) and rutaecarpine ( L C 5 0 = 1 2 0 . 8 5 μg/mL) exhibited stronger nematocidal activity against M. incognita than the crude ethanol extract of E. rutaecarpa ( L C 5 0 = 1 3 1 . 5 4 μg/mL). Wuchuyuamide I, evodol, and limonin also possessed nematocidal activity against M. incognita with LC 50 values of 147.87  μg/mL, 155.02  μg/mL, and 197.37  μg/mL, respectively, but weaker than the crude ethanol extract of E. rutaecarpa.