• Macromolecular Research
• /
• v.13 no.3
• /
• pp.194-205
• /
• 2005

The network structure of Ni-coated carbon black (NCB) composites filled with phenolic resin was investigated by means of using scanning electron microscopy, viscosity, interfacial tension, shrinkability, Flory-Huggins interaction parameters, and swelling index. The electrical properties of the composites have been characterized by measurement of the specific conductivity as a function of temperature. Additionally, the variation of conductivity with temperature for the composites has been reported and analyzed in terms of the dilution volume fraction, relative volume expansion, and barrier heights energy. The thermal stability of phenolic-NCB composites has been also studied by means of the voltage cycle processes. The experimental data of EMI wave shielding were analyzed and compared with theoretical calculations. The mechanical properties such as tensile strength, tensile modulus, hardness and elongation at break (EB) of NCB-phenolic resin composites were also investigated.

• Natural Product Sciences
• /
• v.23 no.1
• /
• pp.5-8
• /
• 2017

An antimicrobial compound has been isolated from the leaves of Glochidion superbum. The compound was determined as methyl 3, 4, 5-trihydroxybenzoate (methyl gallate), based on ultraviolet (UV), infrared (IR), nuclear magnetic resonance (NMR) and mass spectroscopy (MS) analysis. The isolated compound exhibited potent antimicrobial activity against three clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) by qualitative agar disc diffusion method and quantitative broth dilution method. Agar disc diffusion was done in a dose-dependent manner for each bacterial isolate at disc potencies of 25, 50, 100, and $150{\mu}g/disc$. The zones of inhibition were on average equal to 12.27, 14.20, 15.43, and 24.17 mm respectively. The inhibition zones were compared with that of vancomycin disc at $30{\mu}g$ as a reference standard. The MIC and MBC values were $50{\mu}g/ml$ and $100{\mu}g/ml$ respectively. The results of anti MRSA activity were analyzed using one-way ANOVA with Turkey's HSD and Duncan test. In conclusion, methyl gallate which was isolated from G. superbum showed the inhibition activity against methicillin resistant S. aureus.

• Journal of the Korean Society of Tobacco Science
• /
• v.20 no.2
• /
• pp.172-177
• /
• 1998

The culture filtrate of Streptomyces sp. B25, which was identified in this experiment, was tested for the control of tobacco mosaic virus (TMV) with the susceptible tobacco cultivar, NC 82, under the field conditions following the preliminary examination of its characters for TMV control. Control efficacy of the culture filtrate against TMV infection continued over 50% up to 6 days after treatment, and its systemic effect was about 30% of the direct effect. In field conditions control efficacy of the culture filtrate against TMV infection was 95.3 % at 2 weeks after TMV inoculation, and decreased to 58.3 % at 3 weeks after inoculation. Five fold-dilution of the culture filtrate showed about half of the control efficacy by the stock culture filtrate. Analysis of the antibiotic material responsible for the inhibition of TMV infection through nuclear magnetic resonance experiments revealed that the antibiotic is antimycin $A_1$, which is firstly reported as an anti-phytoviral antibiotic in this experiment.

• Journal of the Korean Chemical Society
• /
• v.30 no.1
• /
• pp.126-134
• /
• 1986

7-Alkyl-2-aminophenazine-5,10-dioxides bearing butyl, hexyl and octyl group were synthesized by the reaction of 4-aminophenol with 6-alkylbenzofuroxans which had been obtained from aniline and n-alkyl alcohols. And 2-aminophenazine-5,10-dioxide was prepared by the reaction of 4-aminophenol with benzofuroxan. Infrared, nuclear magnetic resonance spectrophotometers, and elemental analyzer were employed to identify the products concerned with the synthetic processes. Surface tension of aqueous solutions of these phenazine derivatives was determined by surface tensiometer and it was found that the surface tension decreased with an increase of the number of carbon in the alkyl group. Antimicrobial activities were evaluated in terms of minimum inhibitory concentration by a dilution method. The butyl derivative showed the highest activity among these derivatives. It was observed that the antimicrobial activity of these alkyl substituted 2-aminophenazine-5,10-dioxides was stronger than that of 2-aminophenazine-5,10-dioxide.

• Journal of Food Hygiene and Safety
• /
• v.16 no.4
• /
• pp.264-273
• /
• 2001

Antimicrobial activities of ave different probiotics (Lactobacillus reuteri, L. acidophillus, L. bulgaricus, L. casei and Bifidobacterium longum) against 8 bacterial pathogens were determined on the Mueller Hinton Agar containing supernatant of probiotics obtained from 3 different growth conditions (MRS without glycerol, MRS with 0.5 M glycerol or 0.25 M glycerol solution). Though antimicrobial activity of L. reuteri in the first two conditions was not better than the others', the activity was significantly higher than that of others in 0.25 M glycerol solution. This prominent effect might be attributable to reuterin, produced by L. reuteri using glycerol. We could detect the presence of reuterin in the supernatant of 0.25 M glycerol solution with 500 MHz Nuclear Magnetic Resonance (NMR). The result of minimum bactericidal concentration (dilution fold) has revealed that reuterin showed pan-bactericidal effects against 8 major food-borne pathogens. To examine any changes of antimicrobial activities of the probiotics, the probiotics were treated with different pH conditions, pepsin or trypsin digestion. Antimicrobial activity of reuterin was not entirely affected by any of these treatments, while the activities of the other probiotics were significantly decreased.