• Bulletin of the Korean Chemical Society
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• 제28권11호
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• pp.2009-2014
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• 2007

The aminolysis of diphenyl thiophosphinic chloride (2) with substituted anilines in acetonitrile at 55.0 oC is investigated kinetically. Kinetic results yield large Hammett ρX (ρnuc = ?3.97) and Bronsted βX (βnuc = 1.40) values. A concerted mechanism involving a partial frontside nucleophilic attack through a hydrogen-bonded, four-center type transition state is proposed on the basis of the primary normal kinetic isotope effects (kH/kD = 1.0-1.1) with deuterated aniline (XC6H4ND2) nucleophiles. The natural bond order charges on P and the degrees of distortion of 42 compounds: chlorophosphates [(R1O)(R2O)P(=O)Cl], chlorothiophosphates [(R1O)(R2O)P(=S)Cl], phosphonochloridates [(R1O)R2P(=O)Cl], phosphonochlorothioates [(R1O)R2P(=S)Cl], chlorophosphinates [R1R2P(=O)Cl], and chlorothiophosphinates [R1R2P(=S)Cl] are calculated at the B3LYP/ 6-311+G(d,p) level in the gas phase.

• Safety and Health at Work
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• 제2권2호
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• pp.97-104
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• 2011

N,N-Dimethylformamide (DMF) is globally used as an organic solvent in the production of synthetic leather and resins because of its low volatility, making it an attractive industrial material. Despite its excellent property as a chemical solvent, utilization of DMF is somewhat controversial nowadays due to its hazardous effects on exposed workers in work places. Many toxification cases are being reported globally and the number of cases of liver damage is still increasing in developing countries. On account of this, a series of epidemiologic surveys are being conducted to understand the degrees of liver damage caused by DMF exposure. Furthermore, many investigations have been performed to clarify the mechanism of DMF-induced liver toxicity using both human and experimental animal models. This review summarizes the current occupational cases reported on liver damage from workers exposed to DMF in industrial work places and the research results that account for DMF-induced liver failure and possible carcinogenesis. The findings reviewed here show the synergistic toxicity of DMF exposure with other toxicants, which might occur through complicated but distinct mechanisms, which may extend our knowledge for establishing risk assessments of DMF exposure in industrial work places.

• Safety and Health at Work
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• 제8권4호
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• pp.329-336
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• 2017

A review study was conducted to examine the adverse effects of styrene, styrene mixtures, or styrene and/or styrene mixtures and noise on the auditory system in humans employed in occupational settings. The search included peer-reviewed articles published in English language involving human volunteers spanning a 25-year period (1990-2015). Studies included peer review journals, caseecontrol studies, and case reports. Animal studies were excluded. An initial search identified 40 studies. After screening for inclusion, 13 studies were retrieved for full journal detail examination and review. As a whole, the results range from no to mild associations between styrene exposure and auditory dysfunction, noting relatively small sample sizes. However, four studies investigating styrene with other organic solvent mixtures and noise suggested combined exposures to both styrene organic solvent mixtures may be more ototoxic than exposure to noise alone. There is little literature examining the effect of styrene on auditory functioning in humans. Nonetheless, findings suggest public health professionals and policy makers should be made aware of the future research needs pertaining to hearing impairment and ototoxicity from styrene. It is recommended that chronic styrene-exposed individuals be routinely evaluated with a comprehensive audiological test battery to detect early signs of auditory dysfunction.

• Bulletin of the Korean Chemical Society
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• 제9권1호
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• pp.1-4
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• 1988

Rates of solvolysis of trans-[Co$(N-eten)_2Cl_2$]$^+$ have been investigated using spectrophotometric method at various pressures and temperatures in the mixtures of water with the t-butyl alcohol which possesses a high structure inducing capacity in water. The values of ${\Delta}V^{\neq}$ obtained from pressure effect on the rate constants were 2.55∼ 5.83 $cm^3mol^{-1}$. These values were discussed in terms of dissociative mechanism. Extrema found in the variation of ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$ with solvent composition correlated with extrema in the variation of the physical properties of the mixtures. The logarithms of rate constants correlated linearly with both Grunwald-Winstein parameter and the reciprocal of dielectric constant ($Ds^{-1}$). The gradient, m of Grunwald-Winstein plot for the trans-[Co$(N-eten)_2Cl_2$]$^+$ was 0.09, which is significantly lower than those for the other cobalt (Ⅲ)-dichloro complexes. It was suggested that the reaction is an Id mechanism with long extension of Co-Cl bond in the transition state, as found for the C-Cl bond in the transition state for the solvolysis of t-butyl chloride.

• Bulletin of the Korean Chemical Society
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• 제22권1호
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• pp.25-29
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• 2001

Nucleophilic substitution reactions of O-imidomethyl derivatives of phenols with OH- were studied theoretically using the semiempirical AM1 and Solvation Model 2.1 (SM2.1) methods in the gas phase and aqueous solution, respectively. In the gas phase, the two reaction paths, in which the imide (1a) or phenol (1b) is functioning as a leaving group, can occur competitively. In contrast, in aqueous solution, path (1b) becomes more favorable than (1a) because the transition states (TS) of path (1b) are more stabilized by solvent. Differences in solvation energies are caused by the structural differences of TS, i.e., the TS via path (1b) is more dissociative than that via path (1a). Therefore we conclude that the solvent effects play an important role in the hydrolysis of O-imidomethyl derivatives of phenols. However, reactivity is dependent on the acidities of both the imide and the phenol fragments since the ρz values vary progressively from 4.2 (Z' = I) to 2.5 (Z' = IV) as the acidities of imide increase. These are in good agreement with the experimental results.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.968-973
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• 1998

Solvolyses of para-substituted phenyl chloroformates in water, $D_2O,\;CH_3OD$, 50% $D_2O-CH_3OD$, and in aqueous binary mixtures of acetone, ethanol, methanol are investigated at 25.0 ℃. Product selectivities are reported for a wide range of ethanol-water and methanol-water solvent compositions. These data are interpreted using the Grunwald-Winstein relationship, Hammett equation, and quantum mechanical model. Grunwald-Winstein plots of the first-order rate constants for phenyl chloroformates with $Y_{Cl}$ (based on 1-adamantyl chloride) show marked dispersions into three separate curves for the three aqueous mixtures with a small m value and a rate maximum for aqueous alcohol solvents. To account for these results, third-order rate constants, $k_{ww},\;k_{aw},\;k_{wa}$, and $k_{aa}$ were calculated from the observed $k_{ww}\;and\;k_{aa}$ values together with $k_{aw}\;and\;k_{wa}$ calculated from the computer fit. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed carbonyl addition-elimination for para-substituted phenyl chloroformates solvolyses based on mass law and stoichiometric salvation effect studies. This study has shown that the quantum mechanical model predicts transition state variation correctly for $S_N2\;like\;S_AN$ reaction mechanism of para-substituted phenyl chloroformates.

• 대한의생명과학회지
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• 제28권1호
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• pp.34-41
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• 2022

In this study, conditions for extraction of functional component from Nypa fruticans wurmb was optimized. The yield by extraction with 30% ethanol (LE30, 42.12%) was higher than those hot water extraction (LDW 33.32%), 50% ethanol (LE50, 40.12%) and 70% ethanol (LE70, 34.5%). The extract was purified and analyzed by GC MS. The prevailing compounds found in extract were Cyclodecasiloxane-, pentadecanoic acid, -eicosane, undecanal and tridecanoic acid. The presence of saturated and unsaturated fatty acids in ethanolic extract vindicate the use of this plant to treat many diseases in traditional medicine. The total phenolic contents in the LDW, LE30, LE50, LE70 extract were 128±1.65 mg/g, 205±2.3 mg/g, 210±4.23 mg/g and 180±5.6 mg/g, respectively. The DPPH was highest in LE70 extract (1,000 ㎍/mL, 81.14%), ABTS was highest in LE50 extract (1,000 ㎍/mL, 84.14%). The protective effects against oxidative stress in raw 264.7 cell imparted by the LE50 extract was better than those imparted by the other extracts. The findings of the present study suggest that 50% ethanol is best solvent for extraction of Nypa fruticans Wurmb, considering yield, polyphenol content, and antioxidant activities with extraction cost.

• 한국수산과학회지
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• 제56권1호
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• pp.28-32
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• 2023

We optimized ultrasound-assisted extraction to improve the extraction efficiency of bioactive compounds from the microalgae Acutodesmus reginae. To optimize this extraction process, we investigated the effects of solvent type, solvent concentration, extraction time, extraction number, and extraction power on the production of lutein, α-carotene, β-carotene, and chlorophylls a, and b. After sequential optimization of these main variables, the maximum amount of each compound was extracted at 30℃ with an ultrasound power of 80 W and using 99.5% methanol. Under these optimum conditions, the amount of lutein, α-carotene, β-carotene, and chlorophylls a, and b, were measured as 10.43, 8.66, 3.76, 15.43, and 6.39 mg/g dry matter respectively.

• Journal of Nutrition and Health
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• 제36권2호
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• pp.133-146
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• 2003

This study was performed to investigate the in vitro and in vivo anticancer effects of persimmon leaf extracts on human gastric cancer cells. In vitro anticancer effects of persimmon leaf extracts (water extract at 8$0^{\circ}C$ for 3 hours, water extract at room temperature for 48 hours, 50% ethanol extract at 8$0^{\circ}C$ for 3 hours, 50% ethanol extract at room temperature for 48 hours, 75% ethanol extract at 8$0^{\circ}C$ for 3 hours and 75% ethanol extract at room temperature for 48 hours) on SNU16 (Korean gastric cancer cell) were investigated by MTT assay. Persimmon leaf extracts exhibited strong in vitro anticancer effects. We found that the higher the ethanol content of the solvent, the stronger the in vitro anticancer effects. Extraction yields, contents of flavonoids, vitamin A, vitamin C and vitamin E were measured. We found that the higher the ethanol content of the solvent, the higher the extraction yields and the contents of flavonoids, vitamin A and vitamin E. Among persimmon leaf extracts, 75% ethanol 8$0^{\circ}C$ extract showed the highest extraction yield, the highest contents of flavonoids, vitamin A and vitamin E and exhibitied the strongest in vitro anticancer effect on SNU16. Therefore, 75% ethanol 8$0^{\circ}C$ extract was chosen as the material to investigate in vivo anticancer effects. In vivo anticancer effect of persimmon leaf 75% ethanol 8$0^{\circ}C$ extract was investigated in SNU16 transplanted nude mice. Twenty five female nude mice (BALB/c) were blocked into five groups according to body weight and raised for 4 weeks with diets containing 4% (w/w), 8% (w/w) persimmon leaf 75% ethanol 8$0^{\circ}C$ extract, with IT (intratumoral) injection treatment with 1.65 mg/100 $\mu$1, 3.3 mg/100 $\mu$1 concentration every other day 3 weeks after SNU16 was transplanted. Persimmon 75% ethanol 8$0^{\circ}C$ extract significantly lowered tumor weight and tumor volume in SNU16 transplanted nude mice. Tumor weight and tumor volume in all experimental groups were significantly lower than those in the control group. Helper T cell (CD4) levels of mice injected with 3.3 mg/100 $\mu$1 extract significantly increased. Cytotoxic T cell (CD8) levels in all experimental groups significantly increased and helper/cytotoxic T cell ratios in all experimental groups significantly decreased. Natural killer cell and MHC class II molecule in all experimental groups significantly increased. In conclusion, persimmon leaf 75% ethanol 8$0^{\circ}C$ extract exhibited strong in vitro and in vivo anticancer effects against SNU16 cells and it increased cytotoxic T cell, natural killer cell and MHC classII molecule in experimental groups in SNU16 transplanted nude mice.

• 한국식품과학회지
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• 제32권4호
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• pp.928-935
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• 2000

오미자 종자의 몇가지 용매 추출물과 분획물의 항산화성, 항균성, 아질산염 소거능에 대하여 확인한 결과 다음과 같다. 돈지와 linoleic acid에 대한 항산화력은 오미자종자의 methanol 추출물이, 대두유는 ethanol 추출물이 가장 효과적이었으며 free radical 소거 활성은 methanol추출물의 ethyl acetate 분획에서 DPPH free radical 소거 활성이 가장 컸다. 오미자 종자 추출 용매별 항균 효과는 L. planterum, B. subtilis, E. coli, P. citrinium는 methanol 추출물이, S. aureus와 S. typhimurium은 ethyl acetate 추출물의 항균 활성이 가장 컸다. 전반적으로 항균 활성이 큰 methanol 추출물을 분획하여 항균력을 검토한 바, buthanol 분획물이 L. planterum, B. subtilis, S. aureus, S. typhimurium 및 E. coli에서 항균 활성이 가장 강하였다. 아질산염 소거 효과는 반응 pH가 낮을수록 우수했으며 methanol 추출물의 buthanol 분획이 다른 추출물과 분획물 중에서 가장 높은 아질산염 분해능을 나타내었다.