Hyo-Rim Lee

Larvicidal and Acetylcholinesterase Inhibitory Activities of Apiaceae Plant Essential Oils and Their Constituents against Aedes albopictus and Formulation Development

This study evaluated the larvicidal activity of 12 Apiaceae plant essential oils and their components against the Asian tiger mosquito, Aedes albopictus, and the inhibition of acetylcholine esterase with their components. Of the 12 plant essential oils tested, ajowan (Trachyspermum ammi), caraway seed (Carum carvi), carrot seed (Daucus carota), celery (Apium graveolens), cumin (Cuminum cyminum), dill (Anethum graveolens), and parsley (Petroselinum sativum) resulted in >90% larval mortality when used at 0.1 mg/mL. Of the compounds identified, α-phellandrene, α-terpinene, p-cymene, (-)-limonene, (+)-limonene, γ-terpinene, cuminaldehyde, neral, (S)-+-carvone, trans-anethole, thymol, carvacrol, myristicin, apiol, and carotol resulted in >80% larval mortality when used at 0.1 mg/mL. Two days after treatment, 24.69, 3.64, and 12.43% of the original amounts of the celery, cumin, and parsley oils, respectively, remained in the water. Less than 50% of the original amounts of α-phellandrene, 1,8-cineole, terpinen-4-ol, cuminaldehyde, and trans-antheole were detected in the water at 2 days after treatment. Carvacrol, α-pinene, and β-pinene inhibited the activity of Ae. albopictus acetylcholinesterase with IC50 values of 0.057, 0.062, and 0.190 mg/mL, respectively. A spherical microemulsion of parsley essential oil-loaded poly(vinyl alcohol) (PVA) was prepared, and the larvicidal activity of this formulation was shown to be similar to that of parsley oil.

Fumigant Toxicity of Lamiaceae Plant Essential Oils and Blends of Their Constituents against Adult Rice Weevil Sitophilus oryzae

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.

Identification of the Aggregation-sex Pheromone Produced by Male Monochamus saltuarius, a Major Insect Vector of the Pine Wood Nematode

In this study, we isolated and identified an aggregation-sex pheromone from Monochamus saltuarius, the major insect vector of the pine wood nematode in Korea. Adult males of M. saltuarius produce 2-undecyloxy-1-ethanol, which is known as an aggregation-sex pheromone in other Monochamus species. We performed field experiments to determine the attractiveness of the pheromone and other synergists. More M. saltuarius adult beetles were attracted to traps baited with the pheromone than to unbaited traps. Ethanol and (−)-α-pinene interacted synergistically with the pheromone. Traps baited with the pheromone + (−)-α-pinene +ethanol were more attractive to M. saltuarius adults than traps baited with the pheromone, (−)-α-pinene, or ethanol alone. Ipsenol, ipsdienol, and limonene were also identified as synergists of the aggregation-sex pheromone for M. saltuarius adults. In field experiments, the proportion of females was much higher in the beetles caught in traps than among the beetles emerging from naturally-infested logs in the laboratory. Our results suggest that a combination of aggregation-sex pheromone and synergists could be very effective for monitoring and managing M. saltuarius.

Repellent Activity of Apiaceae Plant Essential Oils and their Constituents Against Adult German Cockroaches

Abstract We evaluated the repellent activity of 12 Apiaceae plant essential oils and their components against male and female adult German cockroaches, Blattella germanica L., to find new natural repellents. Of all the plant essential oils tested, ajowan (Trachyspermum ammi Sprague) and dill (Anethum graveolens L.) essential oils showed the most potent repellent activity against male and female adult German cockroaches. Repellent activities of chemicals already identified in active oils were also investigated. Of the compounds identified, carvacrol, thymol, and R-(-)-carvone showed >80% repellent activity against male and female adult German cockroaches at 2.5 µg/cm2. S-(+)-Carvone, (+)-dihydrocarvone, and terpinen-4-ol showed >70% repellent activity against male and female adult German cockroaches at 10 µg/cm2. Our results indicated that Apiaceae plant essential oils and their constituents have good potential as natural repellents against adult German cockroaches.

Antifungal activities after vaporization of ajowan (Trachyspermum ammi) and allspice (Pimenta dioica) essential oils and blends of their constituents against three Aspergillus species

Abstract The fumigant antifungal activities of ajowan (Trachyspermum ammi), and allspice (Pimenta dioica) essential oils and their constituents were tested against three Aspergillus species: A. ochraceus, A. parasiticus, and A. niger. Ajowan essential oil demonstrated a 100% inhibition rate against these three Aspergillus species at an air concentration of 56 × 10−3 mg/mL. The fumigant antifungal activities of allspice essential oil against A. niger, A. ochraceus, and A. parasiticus were 100, 84.4, and 83.5%, respectively. Gas chromatography-mass spectrometry analysis led to the identification of twelve compounds in ajowan oil and six compounds in allspice oil. Of the compounds tested, thymol, carvacrol, and eugenol showed strong inhibitory activity against the three Aspergillus species. The fumigant antifungal activities of blends of the constituents identified in ajowan and allspice oils indicated that thymol and eugenol were the major contributors to the fumigant antifungal activities of ajowan and allspice oils, respectively.

Larvicidal and Nematicidal Activities of 3-Acylbarbituric Acid Analogues against Asian Tiger Mosquito, Aedes albopictus, and Pine Wood Nematode, Bursaphelenchus xylophilus

Widespread concern for the occurrence of resistant strains, along with the avoidance of the use of highly toxic insecticides and their wide environmental dispersal, highlights the need for the development of new and safer pest control agents. Natural products provide inspiration for new chemical entities with biological activities, and their analogues are good lead compounds for the development of new pest control agents. For this purpose, we evaluated the larvicidal and nematicidal activities of 48 3-acylbarbituric acid analogues against the Asian tiger mosquito, Aedes albopictus and the pine wood nematode, Bursaphelenchus xylophilus, organisms of increasing global concern. Among the 48 3-acylbarbituric acid analogues, four compounds—10, 14d, 14g and 19b—showed >90% larvicidal activity against Ae. albopictus at 10 μg/mL concentration, and one (compound 10) showed the strongest larvicidal activity against Ae. albopictus, with a LC50 value of 0.22 μg/mL. Only compound 18 showed strong nematicidal activity against pine wood nematode. Most active compounds possessed similar physicochemical properties; thus, actives typically had ClogP values of around 1.40–1.50 and rel-PSA values of 16–17% and these similar cheminformatic characteristics reflect their similar structure. This study indicates that active 3-acylbarbituric acids analogues have potential as lead compounds for developing novel mosquito control agents.

Synergic effect of sex pheromone (7R,8S)-cis-7,8-epoxy-2-methyloctadec-17-ene on (+)-disparlure of the Asian gypsy moth, Lymantria dispar, in Korea

Abstractfield attraction test of (7R,8S)-cis-7,8-epoxy-2-methyloctadec-17-ene (= 7R,8S-epo-2me-17ene-18Hy), a trace component of the sex pheromone gland of the Asian gypsy moth, (Lymantria dispar), traps that were baited with the trace component attracted more L. dispar than traps baited with (7S,8R)-cis-7,8-epoxy-2-methyloctadec-17-ene (= 7S,8R-epo-2me-17ene-18Hy) and unbaited traps. However, traps baited with 7R,8S-epo-2me-17ene-18Hy were less attractive than traps baited with (+)-disparlure [= (7R,8S)-cis-7,8-epoxy-2-methyloctadecane], the sex pheromone of L. dispar. Combination tests with (+)-disparlure, 7R,8S-epo-2me-17ene-18Hy, and 7S,8R-epo-2me-17ene-18Hy revealed that 7R,8S-epo-2me-17ene-18Hy acted synergistically with (+)-disparlure.

Insecticidal Activity of Lamiaceae Plant Essential Oils and Their Constituents Against Blattella germanica L. Adult

The insecticidal activities of 13 Lamiaceae plant oils and their components against adult German cockroaches, Blattella germanica L. (Blattodea: Blattellidae), were evaluated using fumigant and contact bioassay. Among the tested oils, basil, pennyroyal, and spearmint showed the strongest insecticidal activities against adult B. germanica. Insecticidal activity of pennyroyal was 100% against male B. germanica at 1.25 mg concentration in fumigant bioassay. Basil and spearmint revealed 100% and 100% insecticidal activity against male B. germanica at 5 mg concentration, but their activities reduced to 80% and 25% at 2.5 mg concentration, respectively. In contact, toxicity bioassay, basil, pennyroyal, and spearmint oils exhibited 100%, 100%, and 98% mortality against female B. germanica at 1 mg/♀, respectively. Among the constituents identified in basil, pennyroyal, and spearmint oils, insecticidal activity of pulegone was the strongest against male and female B. germanica.

Identification of Aggregation-Sex Pheromone of the Korean Monochamus alternatus (Coleoptera: Cerambycidae) Population, the Main Vector of Pine Wood Nematode

Abstract We confirmed an aggregation-sex pheromone of the Korean Monochamus alternatus Hope (Coleoptera: Cerambycidae) population, which primarily transmitted the pine wood nematode in Korea. Only the M. alternatus male emitted monochamol which has been previously reported in the Chinese M. alternatus population. In field attraction testing, the monochamol+α-pinene+ethanol combination attracted more M. alternatus adult beetles than traps containing only monochamol, ethanol, or α-pinene. The bark beetle aggregation pheromone compounds of ipsenol, ipsdienol, and ipsenol+ipsdienol, did not show synergistic effects with the monochamol+α-pinene+ethanol combination. No synergistic effects were observed when each host volatile compound of 3-carene, β-caryophyllene, limonene, myrcene, and β-pinene was added to traps containing monochamol+α-pinene+ethanol. The ratio of female beetles was much higher in traps containing the monochamol+α-pinene+ethanol combination than that of the natural population. Our results indicated that pheromone and synergists could be useful for managing the M. alternatus population.

Nematicidal Activity of 3-Acyltetramic Acid Analogues Against Pine Wood Nematode, Bursaphelenchus xylophilus

Among 98 3-acyltetramic acid analogues, compounds 1c, 2c, 2f and 2g, showed >90% nematicidal activity against the pine wood nematode Bursaphelenchus xylophilus at a 10 μg/mL concentration. The nematicidal activities of compounds 1d, 1h, and 2k were a little lower at 88.0%, 85.8%, and 57.2% at a 10 μg/mL concentration, respectively. The nematicidal activity of emamection benzoate, widely used in Korea for the prevention of pine wilt disease, was 32.3% at a 10 μg/mL concentration. Other 3-acyltetramic acid analogues showed less than 30% nematicidal activity. A structure-activity relationship study indicated that the chain length of the C-acyl substituent was very important for high nematicidal activity. All active compounds had C13H27 or C11H23 acyl substituents, in two closely related groups with the common physicochemical properties of a polar surface area 57.6A2, PSA (polar surface area) 7.8–8.6% and ClogP (calculated partition coefficient) 5.1–5.9 and a polar surface area 75–84A2, PSA 11.1–11.6% and ClogP 4.7–5.1, respectively. Our study indicates that active 3-acyltetramic acid analogues could have potential as lead compounds for developing novel pine wood nematode control agents.