Hoi-Seon Lee

Insecticidal and acaricidal activity of carvacrol and β-thujaplicine derived from Thujopsis dolabrata var. hondai sawdust.

Insecticidal and acaricidal components from sawdust of Thujopsis dolabrata var. hondai against eight species of anthropod pests (Reticulitermes speratus, Lasioderma serricorne, Callosobruchus chinensis, Sitophilus oryzae, Plutella xylostella, Myzus persicae, Blatella germanica, and Tetranychus urticae) were isolated by chromatographic techniques and characterized by spectroscopic analyses as the terpenoids carvacrol and β-thujaplicine. In tests using the filter paper diffusion method, carvacrol had broad insecticidal and acaricidal activity against agricultural, stored-product, and medical arthropod pests. However, β-thujaplicine showed only weak termiticidal activity. Insecticidal activity of carvacrol was attributable to fumigant action. As a naturally occurring insecticide, carvacrol could be useful as a new preventive agent against damage caused by these arthropod pests.

Purification and characterization of neutral and alkaline invertase from carrot

Neutral and alkaline invertase were identified in cells of a suspension culture of carrot (Daucus carota L.) and purified to electrophoretic homogeneity. Neutral invertase is an octamer with a molecular mass of 456 kD and subunits of 57 kD, whereas alkaline invertase is a tetramer with a molecular mass of 504 kD and subunits of 126 kD. Both enzymes had sharp pH profiles, with maximal activities at pH 6.8 for neutral invertase and pH 8.0 for alkaline invertase, and both hydrolyzed sucrose with typical hyperbolic kinetics and similar Km values of about 20 mM at pH 7.5. Neutral invertase also hydrolyzed raffinose and stachyose and, therefore, is a [beta]-fructofuranosidase. In contrast, alkaline invertase was highly specific for sucrose. Fructose acted as a competitive inhibitor of both enzymes, with Ki values of about 15 mM. Glucose was a noncompetitive inhibitor of both neutral and alkaline invertase, with a Ki of about 30 mM. Neither enzyme was inhibited by HgCl2. Alkaline invertase was markedly inhibited by CaCl2, MgCl2, and MnCl2, and neutral invertase was not. In contrast to alkaline invertase, neutral invertase was inhibited by the nucleotides ATP, CTP, GTP, and UTP.

Insecticidal Activity of Plant Essential Oils Against Pediculus humanus capitis (Anoplura: Pediculidae)

Abstract The insecticidal activity of 54 plant essential oils against female Pediculus humanus capitis De Geer was examined using direct contact and fumigation methods, and compared with the lethal activity of δ-phenothrin and pyrethrum, two commonly used pediculicides. In a filter paper contact bioassay with female P. humanus capitis, the pediculicidal activity was more pronounced in eucalyptus, marjoram, pennyroyal, and rosemary oils than in δ-phenothrin and pyrethrum on the basis of LT50 values at 0.0625 mg/cm2. At 0.125 mg/cm2, pediculicidal activity of cade, cardamone ceylon, clove bud, myrtle, rosewood, and sage oils was comparable with that of the test insecticides. In fumigation tests with female P. humanus capitis at 0.25 mg/cm2, eucalyptus, marjoram, pennyroyal, and rosemary oils were more effective in closed containers than in open ones, indicating that the effect of these oils was largely a result of action in the vapor phase. Neither δ-phenothrin nor pyrethrum exhibited fumigant toxicity. The essential oils described herein merit further study as potential control agents for P. humanus capitis.

Mosquito larvicidal activity of aromatic medicinal plant oils against Aedes aegypti and Culex pipiens pallens.

ABSTRACT Larvicidal activity of essential oils derived from 11 aromatic medicinal plants against early 4th-stage larvae of Aedes aegypti and Culex pipiens pallens was tested in the laboratory. At 100 ppm, the essential oils of all plants caused 100% mortality against Ae. aegypti and Cx. pipiens pallens. At 25 ppm, the essential oils of Citrus bergamia, Cuminum myrrha, and Pimenta racemosa caused 100% mortality against larvae of Ae. aegypti and Cx. pipiens pallens. The oil of C. bergamia caused 32.5% and 24.5% mortality against Ae. aegypti and Cx. pipiens pallens at 12.5 ppm, but 24.2% and 0% mortality against Ae. aegypti and Cx. pipiens pallens at 6.25 ppm, respectively. The oil of P. racemosa caused 52.3% and 38.5% mortality against Ae. aegypti and Cx. pipiens pallens at 12.5 ppm, but 32.2% and 0% mortality against Ae. aegypti and Cx. pipiens pallens at 6.25 ppm, respectively. The larvicidal activity of oils of C. bergamia, C. myrrha, and P. racemosa was significantly reduced when used at 6.25 ppm. These plants warrant further studies as possible agents for mosquito control.

Growth-Inhibiting Activity of Active Component Isolated from Terminalia chebula Fruits against Intestinal Bacteria

The growth-inhibitory activity of materials derived from the fruit of Terminalia chebula was evaluated against six intestinal bacteria by means of an impregnated paper disk agar diffusion method. The butanol fraction of T. chebula extract had profound growth-inhibitory activity at a concentration of 5 mg per disk. The biologically active component isolated from the T. chebula fruits was identified with a variety of spectroscopic analyses as ethanedioic acid. The growth responses varied in accordance with the bacterial strain, chemical, and dosage tested. In a test with concentrations of 2 and 1 mg per disk, ethanedioic acid had strong and moderate inhibitory activity against Clostridium perfringens and Escherichia coli, respectively, with no associated adverse effects on the growth of the four tested lactic acid-producing bacteria. Ellagic acid derived from T. chebula fruits exerted a potent inhibitory effect against C. perfringens and E. coli, but little or no inhibition was observed with treatments of behenic acid, P-caryophyllene, eugenol, isoquercitrin, oleic acid, ca-phellandrene, 3-sitosterol, stearic acid, a-terpinene, terpinen-4-ol, terpinolene, or triacontanoic acid. These results may be an indication of at least one of the pharmacological properties of T. chebula fruits.

Acaricidal activity of triketone analogues derived from Leptospermum scoparium oil against house-dust and stored-food mites

BACKGROUND Various attempts to control the populations of house-dust and stored-food mites have been implemented using synthetic chemicals. Although effective, the repeated use of these chemicals has led to resistance owing to the mites high reproductive potential and short life cycle. Therefore, this study aimed to develop natural acaricides using oils derived from Leptospermum scoparium JR & G Forst., which may affect the overall biological activity of a mite without adverse effects. Results were compared with those from using benzyl benzoate and N,N-diethyl-3-methylbenzamide (DEET). RESULTS The LD(50) values of L. scoparium oil were 0.54, 0.67 and 1.12 microg cm(-2) against Dermatophagoides farinae (Hughes), D. pteronyssinus (Troussart) and Tyrophagus putrescentiae (Schrank) respectively. The active constituent isolated from L. scoparium was identified as leptospermone (6-isovaleryl-2,2,4,4-tetramethyl-1,3,5-cyclohexanetrione) by spectroscopic analysis. Based on the LD(50) values of leptospermone and its derivatives, the most toxic compound against D. farinae was leptospermone (0.07 microg cm(-2)), followed by 2,2,4,4,6,6-hexamethyl-1,3,5-cyclohexanetrione (1.21 microg cm(-2)), benzyl benzoate (10.03 microg cm(-2)) and DEET (37.12 microg cm(-2)). Furthermore, similar results were observed when the leptospermone and its derivatives were tested against D. pteronyssinus and T. putrescentiae. CONCLUSIONS These results indicate that L. scoparium oil-derived materials, particularly leptospermone and 2,2,4,4,6,6-hexamethyl-1,3,5-cyclohexanetrione, have potential for development as new agents for the control of three species of mite.

ROD-SHAPED IRON OXIDE NANOPARTICLES ARE MORE TOXIC THAN SPHERE-SHAPED NANOPARTICLES TO MURINE MACROPHAGE CELLS

Variable sizes of nanoparticles, ranging from nano to micro scale, are of toxicological interest. In the present study, the authors hypothesized that, in addition to the size, the shape of iron oxide (Fe2O3) nanoparticles is a major factor that contributes to particle cytotoxicity. Cytotoxicity to mouse macrophage cells (RAW 264.7) was investigated using 3 different particles: micro-sized Fe2 O3 (M-Fe2O3), nano-sized Fe2O3 (N-Fe2O3), and rod-shaped Fe2O3 (R-Fe2O3). Whereas M-Fe2O3 and N-Fe2O3 were located in the vacuole as aggregates, R-Fe2 O3 was often spread throughout the cytoplasm. The extent of cytotoxicity measured by the water soluble tetrazolium (WST-1) assay was in the order R-Fe2O3 ≈ N-Fe2O3 > M-Fe2O3, whereas the extent revealed by the lactate dehydrogenase assay was in the order R-Fe2O3 >> N-Fe2O3 ≈ M-Fe2 O3. In addition, the degree of tumor necrosis factor-α and reactive oxygen species (ROS) production was in the order of R-Fe2O3  > N-Fe2 O3 > M-Fe2O3. In addition, a much higher extent of necrosis was associated with the presence of R-Fe2O3. These results suggest that the higher degree of necrosis due to R-Fe2O3 is correlated with both the higher degree of membrane damage and ROS production by R-Fe2O3 compared with the results of the other Fe2O3 particles. These results also showed that the degree of cytotoxicity of nanoparticles should be evaluated based on shape as well as size, because changes in shape and size are accompanied by alterations in surface area, which relate closely to cytotoxicity.

Growth‐Inhibiting Activities of Phenethyl Isothiocyanate and Its Derivatives against Intestinal Bacteria

The growth-inhibiting activities of Sinapis alba L. seed-derived materials were examined on the growth of Bifidobacterium bifidum, B. breve, B. longum, Clostridium difficile, C. perfringens, Escherichia coli, Lactobacillus acidophilus, and L. casei. The active component of S. alba seeds was purified using silica gel column chromatography and HPLC and was identified as phenethyl isothiocyanate by various spectroscopic analyses. The antimicrobial activity of phenethyl isothiocyanate varied according to the dose and bacterial strain tested. Phenethyl isothiocyanate strongly inhibited the growth of C. difficile and C. perfringens at 1 mg/disc, and weakly (+) inhibited its growth at 0.1 mg/disc. Furthermore, phenethyl isothiocyanate moderately (++) inhibited the growth of E. coli at a dose of 2 mg/disc, but did not inhibit the growth of bifidobacteria and lactobacilli. Addition of various functional groups to isothiocyanates resulted in selective inhibitory activity against harmful bacteria with low concentrations of aromatic isothiocyanates demonstrating greater inhibitory activity against clostridia and E. coli than aliphatic isothiocyanates. In conclusion, aromatic isothiocyanates containing phenethyl-, benzyl-, and benzoyl-groups might be useful in the development of novel preventive and therapeutic agents against diseases caused by harmful intestinal bacteria.

Mosquito larvicidal activity of active constituent derived from Chamaecyparis obtusa leaves against 3 mosquito species.

ABSTRACT Mosqutio larvicidal activity of Chamaecyparis obtusa leaf-derived materials against the 4th-stage larvae of Aedes aegypti (L.), Ochlerotatus togoi (Theobald), and Culex pipiens pallens (Coquillett) was examined in the laboratory. A crude methanol extract of C. obtusa leaves was found to be active (percent mortality rough) against the 3 species larvae; the hexane fraction of the methanol extract showed a strong larvicidal activity (100% mortality) at 100 ppm. The bioactive component in the C. obtusa leaf extract was characterized as β-thujaplicin by spectroscopic analyses. The LC50 value of β-thujaplicin was 2.91, 2.60, and 1.33 ppm against Ae. aegypti, Oc. togoi, and Cx. pipiens pallens larvae. This naturally occurring C. obtusa leaves–derived compound merits further study as a potential mosquito larval control agent or lead compound.

Acaricidal activities of apiol and its derivatives from Petroselinum sativum seeds against Dermatophagoides pteronyssinus, Dermatophagoides farinae, and Tyrophagus putrescentiae.

The acaricidal effects of an active constituent derived from Petroselinum sativum seeds and its derivatives were determined using impregnated fabric disk bioassay against Dermatophagoides farinae , Dermatophagoides pteronyssinus , and Tyrophagus putrescentiae and compared with that of synthetic acaricide. The acaricidal constituent of P. sativum was isolated by various chromatographic techniques and identified as apiol. On the basis of LD(50) values against D. farinae and D. pteronyssinus, apiol (0.81 and 0.94 μg/cm(2)) was 12.4 and 10.2 times more toxic than benzyl benzoate (10.0 and 9.58 μg/cm(2)), respectively. In acaricidal studies of apiol derivatives, 3,4-methylenedioxybenzonitrile (0.04, 0.03, and 0.59 μg/cm(2)) was 250, 319, and 20.7 times more toxic than benzyl benzoate (10.0, 9.58, and 12.2 μg/cm(2)) against D. farinae, D. pteronyssinus, and T. putrescentiae. In structure-activity relationships, the acaricidal activities of apiol derivatives could be related to allyl (-C(3)H(5)) and methoxy (-OCH(3)) functional groups. Furthermore, apiol and its derivatives could be useful for natural acaricides against these three mite species.