• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.386-398
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• 1998

In this paper, a high dynamic range IF logarithmic amplifier was designed and fabricated by the successive detection technique for radar systems. The fabricataed IF successive detection logarithmic amplifier(SDLA), a hybrid MIC type, achieves a logarithmic linearity of $\pm$1.4 dB and a dynamic range of 80 dB over 0.5 GHz to 1.5 GHz. The tangential signal sensitivity is -76 dBm, the NF is smaller than 5.5 dB, and the input VSWR is 2.0 : 1. This IF SDLA can be applied to radar systems by reducing the size and power consumption.

• Archives of Pharmacal Research
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• v.20 no.6
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• pp.586-589
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• 1997

Antifungal activities of 6-[(N-4-bromophenyl)amino]-7-chloro-5,8-quinolinedione (RCK7) were tested. The MIC values of RCK7 were determined for antifungal suceptibility, in vitro against Aspergillus niger, Cryptococcus neoformans and Trichophyton mentagrophyte by standard agar streak method. In vitro, RCK7 showed more potent antifungal activity than fluconazole and ketoconazole. Also, RCK7 was tested for in vivo antifungal activity in the treatment of systemic infection with Candida albicans in normal mice. The therapeutic potential of RCK7 had been assessed by evaluating their survival rate against systemic infections compared with that of ketoconazole. $ED_{50}$ of intraperitoneally administered RCK7 ws $2.05{\pm}0.30mg/kg$ but that of ketoconazole was $8.00{\pm}0.73 mg/kg$, respectively. When RCK7 was administered intravenously at the $ED_{50}$(2.05 mg/kg). the colony counts of Candida albicans in the liver after 7 days and 14 days were reduced as likely as ketoconazole at the $ED_{50}(8.00 mg/kg)$, and the better survival rates than ketoconazole's were achieved after 14 days. The results suggest that RCK7 may be a potent antifungal agent.

• Natural Product Sciences
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• v.25 no.2
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• pp.172-180
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• 2019

Infections with Pseudomonas aeruginosa are difficult to treat not only because it is often associated with multidrug-resistant infections but also it is able to form biofilm. The aim of this study was to evaluate the antibiofilm and anti-Quorum Sensing (QS) activities of Thymbra capitata essential oils (EOs) against Beta Lactamase (BL) producing P. aeruginosa and the reference strain P. aeruginosa 10145. GC/MS analysis showed that thymol (23.25%) is the most dominant compound in T. capitata EOs. The MICs of T. capitata EOs against P. aeruginosa (BL) and P. aeruginosa 10145 were 1.11%. At sub MIC (0.041, 0.014 and 0.0046%), the EOs of T. capitata remarkably inhibited the biofilm formation of both strains tested and complete inhibition of the biofilm formation was reported at 0.041%. The EOs of T. capitata were found to inhibit the swarming motility, aggregation ability and hydrophobic ability of P. aeruginosa (BL) and P. aeruginosa 10145. Interestingly, the EOs of T. capitata reduce the production of three secreted virulence factors that regulated by QS system including pyocyanin, rhamnolipids and LasA protease. The potent antibiofilm and anti-QS activities of T. capitata EOs can propose it as a new antibacterial agent to control pseudomonas infections.

• Microbiology and Biotechnology Letters
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• v.48 no.4
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• pp.429-438
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• 2020

The emergence of multi-drug resistant, pathogenic methicillin-resistant Staphylococcus aureus (MRSA) is a threat to global health and has created a need for novel functional therapeutic agents. In this study, we evaluated the underlying mechanisms of the anti-MRSA effect of an azaphilone pigment, sclerotiorin (SCL) from Penicillium sclerotiorum. The antimicrobial activity of SCL was evaluated using agar disc diffusion, broth microdilution, time-kill assays and biophysical studies. SCL exhibits selective activity against Gram positive bacteria including MRSA (range, MIC = 128-1028 ㎍/ml) and exhibited rapid bactericidal action against MRSA with a > 4 log reduction in colony forming units within three hours of administration. Biophysical studies, using fluorescent probes and laser or electron microscopy, demonstrated a SCL dose-dependent alternation in membrane potential (62.6 ± 5.0.4% inhibition) and integrity (> 95 ± 2.3%), and the release of UV260 absorbing materials within 60 min (up to 3.2 fold increase, p < 0.01) of exposure. Further, SCL localized to the cytoplasm and hydrolyzed plasmid DNA. While in vitro checkerboard studies revealed that SCL potentiated the antimicrobial activity of topical antimicrobials such as polymixin, neomycin, and bacitracin (Fractional Inhibitory Concentration Index range, 0.26-0.37). Taken together these results suggest that SCL targets the membrane and DNA of MRSA to facilitate its anti-MRSA antimicrobial effect.

• The Korea Journal of Herbology
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• v.23 no.2
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• pp.1-8
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• 2008

Objectives : The purpose of this study was to evaluate on the antimicrobial effect on the periodontal pathogens and anti-inflammatory effect of Artemisiae Iwayomogii Herba. Artemisiae Iwayomogii Herba has been used for treating as Artemisiae Capilaris Herba in Korea. Methods : Artemisiae Iwayomogii Herba was prepared by extracting medicinal herb with water. We investigated antimicrobial activity by the minimun inhibitory concentration (MIC) test. We also investigated inhibition of IL-$1{\beta}$-induced collagenase-l(MMP-l), stromelysin-1(MMP-3), interleukin-6 gene expression in human gingival fibroblasts. Results : The antimicrobial effect of Artemisiae Iwayomogii Herba was evaluated with MIC against periodontopathogens; Porphyromonas gingivalis 2561, W50, A7A1-28, 9-14K-1, Prevotella intermedia28, and Actinobacillus actinomycetemcomitans Y4, MICs of Artemisiae Iwayomogii Herba were 0.156 mg/ml, 0.625 mg/ml, 0.313 mg/ml, 1.25 mg/ml, 10 mg/ml and 10 mg/ml. The anti-inflammatory effect of Artemisiae Iwayomogii Herba was evaluated with Influence of herbs on the IL-$1{\beta}$-induced expression of MMP-1, MMP-3, interleukin-6, IL-$1{\beta}$ increased MMP-1, MMP-3, interleukin-6 mRNA levels. Artemisiae Iwayomogii Herba significantly inhibited IL-$1{\beta}$-induced MMP-1, MMP-3, interleukin-6 gene expressions in a dose-dependent manner. Conclusions : These results suggested that Artemisiae Iwayomogii Herba might reduce the excessive proteolytic capacity of the gingival fibroblast during inflammation and could be developed a new drug in periodontitis.

• Food Science and Preservation
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• v.11 no.3
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• pp.400-404
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• 2004

This study was conducted to find the antimicrobial activity of garlic extracts by various processing methods(boiled, pan fried, microwave heated, pickled). Ethanol and water extracts from garlic sample were prepared and antimicrobial activities were determined against 10 microoganisms ; food borne pathogens, food poisoning microoganisms, food-related bacteria and yeasts. The ethanol extracts from the fresh and pickled garlic showed antimicrobial activities for test microoganisms, except lactic acid bacteria and yeast. However, the antimicrobial activities were decreased by heat treatment. The minimum inhibitory concentration(MIC) of the fresh garlic extracts was determined to 0.1 mg/mL against an gram positive bacterium and 0.5 mg/mL against an gram negative bacterium. The antimicrobial activities of the ethanol extracts were affected by heating methods and not by pHs.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.1
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• pp.1-11
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• 2009

Essential oils are mixture of volatile, lipophilic compounds originating from plants. Essential oils have potential biological effects, i.e., antibacterial, antifungal, spasmolytic and antiplasmodial activities and insect-repellent property. In this study, five essential oils, namely R, LG, FR, O, and NM, extracted from various aromatic plants were used to test their antimicrobial activity against the oral microorganisms. The effects of essential oils were investigated against eight important bacteria, Streptococcus mutans (S. mutans), Staphylococcus aureus (S. aureus), Streptococcus sanguis (S. sanguis), Streptococcus anginosus (S. anginosus), Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans), Streptococcus sobrinus (S. sobrinus), Staphylococcus epidermidis (S. epidermidis), and Escherichia coli (E. coli). Essential oils, except NM, effectively inhibited the growth of tested oral pathogenic microorganisms dose-dependently. However, the essential oils didn't show a significant inhibitory effect against E. coli and S. epidermidis. Consequently, these results represented that essential oil-mediated anti-microbial activity was prominent against the oral pathogenic bacteria. For example, minimum bactericidal concentration(MBC) of R, LG, FR oil against A. actinomycetemcomitans was very low as 0.078 mg/mL. In addition, minimum inhibitory concentration (MIC) of R, LG, FR, O oil against S. mutans was low as 0.156 mg/mL in vitro.

• Korean Journal of Clinical Laboratory Science
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• v.49 no.3
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• pp.256-262
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• 2017

Essential oil from herb is known to exert pharmacological effects on the human body. In this study we investigated the antibacterial activity of 4 essential oils (teetree, rosemary, melisa, and lavender), as well as the blended mixture oil of teetree, rosemary, and melisa (TRM) on three bacteria, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Antibacterial analysis was performed using the standard disk diffusion method, and minimum inhibition concentration was determined by the broth microdilution method with different concentrations of essential oils (0.5, 1, 2 and 3 mg/mL). After incubation at $37^{\circ}C$ for 24 h, the antibacterial activity was assessed by measuring the zone of growth inhibition surrounding the disks. Herb oil with the inhibition zones showed varied values ranging from6 to 25 mm. However, the components of herb oil of TRM are as highly active as the teetree oil against pathogens, generating large inhibition zones for both gram negative and positive bacteria (13~22 mm and 8 mm inhibition zones). In the analysis for MIC, TRM showed growth-inhibitory effects at 0.0625% for S. aureus and E. coli, and 1.25% for P. aeruginosa. This result demonstrated that the anti-microbial activity of TRM was greater than a single herb oil, including oxacillin, rosemary, and teetrea. As a single herb oil, both rosemary and teetrea also had an anti-microbial effect by itself, and we can expect that the blended oil mixture may exert a synergistic effect against multidrug resistant bacteria, suggesting its future application in natural preservative agents for health food and cosmetics.

• Korean Journal of Food Science and Technology
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• v.38 no.6
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• pp.816-822
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• 2006

The antimicrobial and antioxidative effect of mechanical bamboo smoke distillate (MBSD) and traditional bamboo smoke distillate (TBSD) were investigated. Antimicrobial activity was demonstrated against all the microorganisms used in this experiment and was the higher in TBSD than in MBSD, with an activity concentration in the range 10-50 ${\mu}m/8$ mm paper disc. At the same concentration the antimicrobial activities of TBSD and MBSD was Gram positive bacteria>gram negative bacteria>Lactotobacillus>yeast. The minimum inhibition concentration (MIC) of BSC was 1.0-7.3${\mu}L/mL$, and the maximum lethal concentration (MLC) was 26.7-116.7 ${\mu}L/mL$. The soybean oil oxidative stability increased with increasing BSD concentration. The induction periods of oil oxidation were 3.75, 4.57 and 12.06 days for the samples with BSD added at 0.1%, 0.5%, and 1.0%, respectively. The RAE in soybean oil with 0.5% BSD was evaluated to be 168.45%, being similar to that of the sample with 0.02% BHT.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.7
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• pp.1098-1105
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• 2004

In order to develop natural food preservatives, the ethanol and water extracts of the Saururus chinensis Baill were prepared. Antimicrobial activity was examined against 10 kinds of harmful microorganisms. The ethanol and water extracts showed the most active antimicrobial activity against B. subtilis and E. coli. The ethanol extract showed stronger antimicrobial activity than that of the water extract. However, the extracts did not show any antimicrobial activity against lactic acid bacteria and yeast. The minimum inhibitory concentrations (MIC) of ethanol extracts against B. subtilis and E. coli were 5 to 10 mg/mL, respectively. Antimicrobial activity of the ethanol extract was not destroyed at 40-12$0^{\circ}C$ and pH 3∼11. The ethanol extract was fractionated in the order of hexane, diethyl ether, ethyl acetate, and water fractions. The highest antimicrobial activity was found in the diethyl ether fraction.