• Journal of the Korean Chemical Society
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• v.24 no.4
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• pp.315-321
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• 1980

A steady-state kinetic study on a dye-coupled cytoplasmic polyol dehydrogenase from G. melanogenus was carried by the initial velocity measurements in the direction of the polyol oxidation and the product inhibition by D-fructose. For the initial rate experiments, D-mannitol and D-sorbitol were employed as the specific polyol substrates and 2,6-dichlorophenolin-dophenol (DPIP) as the specific cofactor substrate for the enzyme. When the polyol and DPIP were examined by varying one of substrates and by fixing the second, the corresponding reciprocal plots showed the typical parallel pattern. This suggests that the enzyme from G. melanogenus proceeds by a Ping Pong Bi-Bi mechanism in which the polyol may account as the first reactant-in, and the ketose formed as the first product-out, respectively. The product inhibition patterns obtained by D-fructose (one no-inhibition, one non-competitive, and two competitive) may also provide an additional conformatory evidence for the above mechanism. Based on the kinetic parameters obtained, it was also suggested that the rate-limiting step in the direction of polyol oxidation is associated with the release of the ketose from the Enzyme${\cdot}$Polyol complex.

• Proceedings of the KSCN Conference
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• 2005.04a
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• pp.180-180
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• 2005

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.255.3-256
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• 2002

In the previous studies. we confirmed the anti-inflammatory components of Kalopanax pictus bark using activity-guided fractionation in vivo. For the elucidation of anti-inflammatory mechanism, we evaluated the effects of these components on the inhibition of NF-$\sub$K/B activity and human leukocyte elastase. A cell-based assay system developed in our laboratory was used in transfectant RAW 264.7 cells. (omitted)

• Journal of agriculture & life science
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• v.46 no.2
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• pp.151-162
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• 2012

Four kinds of marketing black garlics (A, B, C and D products) from Namhae were analysed the antioxidant, nitrite scavenging activities and inhibition of nitrosodimethylamine (NDMA) formation. Total pyruvate and thiosulfate contents were higher in the black garlics than fresh garlic, and their contents were the highest in B product. Total phenol and flavonoids contents in the water and 80% ethanol extracts from black garlics were higher in water than ethanol extract, and all black garlics were higher than fresh garlic. And these contents of A product were somewhat higher compared to the others. Antioxidant activities, such as DPPH, ABTs, hydroxyl and nitric oxide radical scavenging showed stronger in water than ethanol extracts. And their activities in all products of black garlic were higher than the extracts of fresh garlic, and their activities of A and B products were similar to each other. In pH 2.5, nitrite scavenging activity and inhibition of NDMA formation were stronger in the black garlics than fresh garlic, and A product was the highest. Moreover, inhibition of NDMA formation from black garlic showed similar trends compared to the antioxidant activities. Therefore, we expect that the black garlic will contribute to the inhibition of carcinogenesis in vivo.

• Journal of the Korean Chemical Society
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• v.5 no.1
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• pp.38-41
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• 1961

By varying groups on biologically active molecules, it is possible to produce analogues which sometimes inhibit the action of the parent compound. Such is true of taurine(${\beta}$-amino-ethane sulfonic acid)as an analogue of ${\beta}$-alanine and of pantoyl taurine for pantothenic acid. It seemed possible that the sulfonic acid analogues of amino acids built into peptides might possibly produce inhibition of the parent peptide. Tauryl-L-histidine was selected to prepare as an analogue of carnosine(${\beta}$-alanyl-L-histidine). There were several reasons for this choice. Camosine causes a slight contraction of isolated uterine muscle and inhibition of this action can be easily tested. Also, taurine, being a ${\beta}$-amino sulfonic acid, is much more stable than the ${\beta}$-amino sulfonic acids. Phthalyl tauryl-L-histidine methyl ester was prepared by condensing phthalyl tauryl chloride with histidine methyl ester in chloroform. The yields were quite low possibly due to reaction between the acid chloride and the imidazole of histidine. Approximately 50 per cent yield of crude amorphous product was obtained, but upon purification by crystallization they yielded only 25 percent of a pure product. The methyl ester was removed by acid hydrolysis to prevent partial cleavage of the phthalyl group. Crystalline tauryl histidine was then obtained from this acid by removal of the phthalyl group by hydrazinolysis. Tests for inhibition were carried out by comparing the action of camosine on isolated uterine muscle before and after tauryl histidine had been added to the bath surrounding the muscle strip. Only in very high relative concentrations of tauryl histidine was there any demonstrable inhibition.

• Natural Product Sciences
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• v.18 no.1
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• pp.1-7
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• 2012

Among 90 Vietnamese medicinal plant extracts investigated for their antioxidant activity by DPPH assay at various concentrations from $10-100{\mu}g/mL$, 67 showed an inhibition rate over 50% at $100{\mu}g/mL$; 47 had greater than 50% inhibition at $50{\mu}g/mL$; 17 showed over 50% inhibition at $25{\mu}g/mL$. 8 extracts which exhibited strong inhibitory activity more than 50% inhibition at $10{\mu}g/mL$ were further tested for lipid peroxidation inhibition by TBA assay. They displayed activity with $IC_{50}$ values from 30.6 to $158.9{\mu}g/mL$. Until now, this is the first report on antioxidant activity of the female flower of Borassus flabellifer, and the stem of Combretum latifolium, Embelia ribes, Spatholobus parviflorus, and Tetrastigma erubescens. Fractionations of the EtOAc extract prepared from S. parviflorus led to the isolation of protocatechuic acid (1), ferulic acid (2), epicatechin (3), and gallic acid (4). These compounds showed significant DPPH inhibitory activity with $IC_{50}$ values from 6.5 to $23.6{\mu}M$.

• Korean Journal of Microbiology
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• v.29 no.2
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• pp.97-103
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• 1991

Glutamine phosphoribosylpyrophosphate amidotransferase of Streptomyces tubercidicus was purified and characterized. Molecular weight of the isolated enzyme was determined to be approximately 230,000 and was composed foru identical subunits having a molecular weight of 58,000. This enzyme was strongly inhibited by AMP while considerably inhibited by ATP and GTP. Inhibition effect of enzyme activity by AMP was antagonized by increased concentration of substrate, PRPP, and metal ion (especially, $Mg^{++}$) was essential in both catalytic activity and nucleotide inhibition of this enzyme. Therefore, it was confirmed that end product inhibition of glutamine phosphoribosylpyrophosphate amidotransferase by adenine participated in the regulation of tubercidin biosynthesis from Streptomyces tubercidicus.s.

• Journal of Microbiology and Biotechnology
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• v.17 no.3
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• pp.543-545
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• 2007

4-Hydroxy-3-(3'-methyl-2'-butenyl)-benzoic acid (HMBA) was previously isolated from Curvularia sp. KF119 as a cell-cycle inhibitor. However, the present study used a novel and practical synthetic method to prepare a large quantity of HMBA. The synthetic HMBA was found to inhibit the cell-cycle progression of HeLa cells with a comparable potency to the natural fungal metabolite. The inhibition of the cell-cycle progression by the synthetic HMBA involved both the activation of $p21^{WAF1}$ and the inhibition of cyclin D1 expression in the cells. Consequently, this new synthetic procedure provides an easy and convenient way to produce or manipulate the original fungal metabolite.

• The Journal of Natural Sciences
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• v.5 no.2
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• pp.63-73
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• 1992

There are many methods of obtaining butadiene described in the literature. In the america it is produced largely from petroleum gases, i.e., by catalytic dehydrogenation of butene of butene-butane mixtures. Butadiene can be recovered from the $C_4$ residue of an olefin plant by distilling off a fraction containing most of the butadiene, catalytically hydrogenating the higher acetylenes to olefins and separating the product from other olefins and isobutane by extraction. Also it can be obtained by cracking naphtha and light oil. Among the individual dienes of commercial importance, 1, 3-butadiene is of first importance. It is used primarily for the production of polymers.In the present paper, it was investigated for a effect of the formation and the growth inhibition of popped corn polymer in butadiene extraction unit. As a result of study, inhibitors, $NaNO_2$ and TBC were good effective for inhibition of the formation and growth in popcorn polymer. The rational formula of popcorn polymer obtained was $(C_4H_6)_x$.

• Natural Product Sciences
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• v.19 no.1
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• pp.8-14
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• 2013

The inhibitory effect and the structure-activity relationships of luteolin and its related derivatives isolated from Taraxacum mongolicum against MAO activities were investigated. The activity-guided isolation of extract from Taraxacum mongolicum led to the isolation of three flavonoids, luteolin, diosmetin, and luteolin-7-glucoside, a polyphenol, chlorogenic acid, a tyrosine and a uridine. The inhibitory activities of luteolin and its related derivatives against MAOs activities are dependent on their molecular structures. The presence of the phenolic hydroxy group at para-position is the active site for MAO-A inhibition as well as of MAO-B. The methoxy group has no potential on MAO-A inhibition. An additional phenolic hydroxy group at the ortho-position alleviates about 4-fold MAO-A inhibitory activity of phenolic hydroxy group at para-position. A carboxylic group seems to be critical for DBH inhibition and has no effects on MAO.