• YAKHAK HOEJI
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• v.45 no.2
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• pp.147-152
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• 2001

The phytochemical study of the aerial parts of Artemisia sylvatica (Asteraceae) led to the isolation of nine sesquiterpene lactones, l$\alpha$-hydroperoxy-rupicolin A acetate (1), rupicolin B acetate (2), rupicolin A acetate (3), l$\alpha$-hydroxy-4$\alpha$-hydroperoxy-bishopsolicepolide (4), 1$\alpha$-hydroperoxy-4$\beta$-hydroxy-8$\alpha$-acetoxy-guaia-2,9,11 (13)-triene-6$\alpha$,12-oxide (5), 1$\alpha$-hydroperoxy-4$\alpha$-hydroxybishopsolicepolide (6), l$\alpha$,4$\beta$-dihydroxy-8$\alpha$-acetoxy-guaia-2,9,11(13)-triene-6$\alpha$,12-olive (7), rupicolin A (8) and l$\alpha$,4$\alpha$-dihydroxy-bishopsolicepolide (9). Their structures were established by chemical and spectroscopic methods.

• Korean Journal of Microbiology
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• v.23 no.4
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• pp.302-308
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• 1985

It is shown by means of nuclear magnetic resonance spectroscopy that 3,4,5-trihydroxy-2-keto-L-valeraldehyde (L-xylosone), an ${\alpha}$-ketoaldehyde, is formed during the oxidative catabolism of L-ascorbic acid. It is proposed that this substance serves as a substrate for the glyoxalase system by which it is transformed to L-xylonic acid. As L-xylonic acid is further oxidized to L-erythroascorbic acid, a biochemical pathway is proposed for the action of vitamin C which consists of two further ${\gamma}$-lactones and three different substrates of the glyoxalase system.

• Journal of the Korean Chemical Society
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• v.41 no.4
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• pp.210-213
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• 1997

• Proceedings of the Korean Society of Life Science Conference
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• 2001.02a
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• pp.69-69
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• 2001

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.120-121
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• 1989

• Bulletin of the Korean Chemical Society
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• v.10 no.3
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• pp.326-327
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• 1989

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.842-845
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• 1998

Four new lactones and one dibenzo crown ether were synthesized by reaction of dihydroxy compound with oxalyl chloride and with ${\alpha}$,${\omega}$-dibromo compound, respectively. 5,6,11,12-Tetracarbonyl-2,2,3,3,8,8,9,9-octaphenyl-1,4,7,10-tetraoxacyclodode- cane(1), 5,6,11,12-tetracarbonyl-2,2,3,3,8,8,9,9-octamethyl-1,4,7,10-tetraoxacyclododecane(2), 7,8,15,16-tetracarbonyl-1,6,9,14-tetraoxacylclohexadecane(3), and 5,6,11,12-tetracarbonyl- 2,3,8,9- tetraphenyl-1,4,7,10-tetraoxacyclododecane(4) were prepared by reaction of oxalyl chloride with benzopinacol, pinacol, 2,2'-dihydroxybiphenyl and hydrobenzoin, respectively, in the presence of pyridine. Dibenzo-13-crown-4 (5) was obtained by reaction of catechol with 1,3-dibromopropane/1,2-dibromoethane.

• Toxicological Research
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• v.17
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• pp.271-280
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• 2001

We report on the applicability oj a method recently developed in our laboratory for measuring the antioxidant potential of isolated chemicals and extracts derived from natural products. Peroxyl radicals generated by thermal homolysis of 2,2'-azobis-amidinopropane (ABAP) oxidize $\alpha$-keto-${\gamma}$-methiolbutyric acid (KMBA) to ethylene, which is monitored by gas chromatography. Inhibition of ethylene formation in the presence of antioxidants that compete with KMBA for peroxyl radicals is the basis of the Total Oxyradical Scavenging Capacity Assay (TOSCA; Winston et al., 1998). Antioxidative activities of water-soluble extracts of American green tea, the anti-hepatotoxic flavonolignan from milk thistle (Silybum marianum) silybin, Ginkgo biloba extract EGb 761, and a series of naturally occuring sesquiterpene lactones (all ger-macranolides found in in fungi, liverworts, and plants) were studied. The specific TOSC value per $\mu$M silybin was 5.2, which is essentially comparable to that of Trolo $x^{ⓡ}$, a water-soluble vitamine E analog. Tea and Ginkgo extracts exhibited potent peroxyl radical scavenging capacity with values, respectively of =1700 and 1000 $\mu$mols Trolo $x^{ⓡ}$ equivalent per gram dry matter. The known anti-inflammatory activity of some germacranolides prompted study of their antioxidant capacity. None of the lactones exhibited antioxidant capacity toward peroxyl radicals comparable to Trolo $x^{ⓡ}$; costunilide, the most lipophilic, had a TOSC value = to glutathione. The potential role of peroxyl radicals in lipidperoxidation, other cellular damage, and var-ious disease states suggest a possible preventive role for silybin, green tea and Ginkgo biloba in oxidative stress caused by these free radical species.ecies.

• Membrane and Water Treatment
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• v.14 no.1
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• pp.35-45
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• 2023

Biofilms significantly affect the performance of wastewater treatment processes in which biodegradability of numerous microorganisms are actively involved, and various technologies have been applied to secure microbial biofilms. Understanding changes in biofilm characteristics by regulating expression of signaling molecules is important to control and regulate biofilms in membrane bioreactor, i.e., biofouling. This study investigated effects of addition of acyl-homoserine lactones (AHL) as a controllable factor for the microbial signaling system on biofilm formation of Pseudomonas aeruginosa PAO1 and multiple strains in membrane bioreactor. The addition of three AHL, i.e., C4-, C6-, and C8-HSL, at a concentration of 200 ㎍/L, enhanced the formation of the PAO1 biofilm and the degree of increases in the biofilm formation of PAO1 were 70.2%, 76.6%, and 72.9%, respectively. The improvement of biofilm formation of individual strains by C4-HSL was an average of 68%, and the microbial consortia increased by approximately 52.1% in the presence of 200 ㎍/L C4-HSL. CLSM images showed that more bacterial cells were present on the membrane surface after the AHL application. In the COMSTAT results, biomass and thickness were increased up to 2.2 times (PAO1) and 1.6 times (multi-strains) by C4-HSL. This study clearly showed that biofilm formation was increased by the application of AHL to individual strain groups, including PAO1 and microbial consortia, and significant increases were observed when 50 or 100 ㎍/L AHL was administered. This suggests that AHL application can improve the biofilm formation of microorganisms, which could yield an enhancement in efficiency of biofilm control, such as in various biofilm reactors including membrane bioreactor and bioflocculent systems in water/wastewater treatment processes.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.1921-1922
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• 2007