• Mass Spectrometry Letters
• /
• v.4 no.3
• /
• pp.55-58
• /
• 2013

Dioscin is a biologically active steroidal saponin with anticancer and hepatoprotective effects. A rapid, selective, and sensitive liquid chromatographic method with electrospray ionization tandem mass spectrometry was developed for the quantification of dioscin in rat plasma. Dioscin was extracted from rat plasma using ethyl acetate at acidic pH. The analytes were separated on a Halo C18 column using gradient elution of acetonitrile and 0.1% formic acid and detected by tandem mass spectrometry in selected reaction monitoring mode. The standard curve was linear ($r^2$ = 0.998) over the concentration range of 1-100 ng/mL. The lower limit of quantification was 1.0 ng/mL using 50 ${\mu}L$ of plasma sample. The coefficient of variation and relative error for intra- and inter-assay at four QC levels were 1.3 to 8.0% and -5.4 to 10.0%, respectively. This method was applied successfully to the pharmacokinetic study of dioscin after oral administration of dioscin at a dose of 29.2 mg/kg in male Sprague-Dawley rats.

• Archives of Pharmacal Research
• /
• v.21 no.6
• /
• pp.651-656
• /
• 1998

A sensitive high-performance liquid chromatographic (HPLC) method for the determination of aloesin in plasma was developed. After solid-phase extraction from plasma and derivatization of aloesin and compound AD-1, which was prepared from aloesin as a internal standard, with 9-anthroylnitrile in the presence of quinuclidine, the derivatives were separated on a Inertsil ODS-3 column using acetonitrile/methanol/water (3:1:6) as a mobile phase, and detected fluorimetrically at 460nm with excitation at 360nm. The detection limit of aloesin was 3.2ng/ml in plasma (S/N=3).

• YAKHAK HOEJI
• /
• v.33 no.4
• /
• pp.241-245
• /
• 1989

A new application of high performance liquid chromatography for the determination of capsaicin and dihydrocapsaicin in cataplasma preparation was investigated. Optimum conditions for a good separation and detection were determined; 0.93 volt, acetonitrile: $H_3PO_4$ sol (pH 2.8), sample size; $7\;{\mu}l$. Recovery rates of capsaicin and dihydrocapsaicin from mixed artificial preparations were 99.9% and 98.4% respectively. Also reproducibility tests showed that the coefficient of variation was 1.59% for capsaicin and 1.14% for dihydrocapsaicin. There was no interference with cataplasma preparation containing thymol, dl-camphor and the commonly encountered excipients or additives such as gelatine, glycerine. This method was rapid, accurate and it gave higher sensitivity than other method.

• Food Science and Biotechnology
• /
• v.17 no.3
• /
• pp.679-682
• /
• 2008

A lactic acid bacterium producing an antimicrobial substance against Escherichia coli O157:H7 was isolated from raw milk and identified as Lactobacillus amylovorus ME-1. In addition to E. coli O157 :H7, the antimicrobial substance also inhibited the growth of Bacillus cereus, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella typhimurium, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pyrogenes, and Yersinia enterocolitica. The antimicrobial substance was stable at pH 2-12 and $121^{\circ}C$ for 15 min and insensitive to proteinase K, protease, amylase, and catalase. Purification of the antimicrobial substance was conducted through methanol and acetonitrile/ethylacetate extraction, ultrafiltration with a 500 Da cutoff, thin layer chromatography (TLC) with silicagel 60, and high performance liquid chromatography (HPLC) with a $C_{18}$ reverse phase column. The ${\lambda}_{max}$ of the purified antimicrobial substance was determined as 192 nm by ultra violet (UV) scanning, while the molecular weight was estimated as 453 Da based on the mass spectrum. Accordingly, the current results suggest that the antimicrobial substance from the L. amylovorus ME-1 was not a bacteriocin, but rather a new non-proteinaceous substance distinct from acidophilin, acidolin, diacetyl, and reuterin.

• Journal of the Korean Chemical Society
• /
• v.28 no.6
• /
• pp.384-392
• /
• 1984

Reaction of the Fe(II) complex of a fully saturated tetradentate macrocyclic ligand [Fe([14]aneN$_4)(CH_3CN)_2]^{2+}$, where [14]ane$N_4$ represents 1,4,8,11-tetraazacyclotetradecane, with $O_2$ has been investigated in acetonitrile solutions. [Fe([14]aneN$_4)(CH_3CN)_2]^{2+}$ reacts with oxygen to yield low spin Fe(III) species, [Fe([14]aneN$_4)(CH_3CN)_2]^{3+}$, which undergoes metal ion assisted oxidative dehydrogenation of the macrocyclic ligand to produce low spin Fe(II) complex, [Fe([14]tetraeneN$_4)(CH_3CN)_2]^{2+}$. The macrocyclic ligand in [Fe([14]tetraeneN$_4)(CH_3CN)_2]^{2+}$ is highly unsaturated and its double bonds are conjugated. [Fe([14]dieneN$_4)(CH_3CN)_2]^{2+}$ and [Fe([14]dieneN$_4)(CH_3CN)_2]^{3+}$ are isolated as the intermediates of the reaction. The Fe(II) complexes involved in this oxidative dehydrogenation reaction react with carbon monoxide to give respective carbon monoxide derivatives, [FeL$(CH_3CN)(CO)]^{2+}$ (where L = macrocyclic ligand). The values of $v_{CO}$ of [FeL$(CH_3CN)(CO)]^{2+}$, and the electrochemical oxidation potentials of Fe(II) ${\to}$ Fe(III) and the qualitative stability toward air-oxidation for [FeL(CH$_3CN_2)^{2+}$ increase as the degree of unsaturation of the macrocyclic ligands increase.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.12
• /
• pp.1981-1985
• /
• 2005

Kinetic studies have been performed for alkaline hydrolysis of a series of [(methoxy)(p-substituted styryl)carbene]pentacarbonyl chromium(0) complexes ($(CO)_5$Cr=$C(OCH_3)CH=CHC_6H_4X$, X = p-$OCH_3$, p-$CH_3$, H, p-Cl, p-$NO_2$). Second-order rate constants $(k_{{OH}^-})$ for the alkaline hydrolysis in 50% acetonitrile-water(v/v) were determined spectrophotometrically at various temperatures. At a low pH region (pH < 7.5), the observed rate constant $(k_{obs})$ remained constant with a small value, while in a high pH region (pH > 9.5), $k_{obs}$ increases linearly with increasing the pH of the medium. The second-order rate constants $(k_{{OH}^-})$ increase as the substituent X changes from a strong electron donating group to a strong electron withdrawing group. The Hammett plot obtained for the alkaline hydrolysis is consisted of two intersecting straight lines. The nonlinear Hammett plot might be interpreted as a change in the rate-determining step. However, the fact that the corresponding Yukawa-Tsuno plot is linear with $\rho$ and r values of 0.71 and 1.14, respectively indicates that the nonlinear Hammett plot is not due to a change in the rate-determing step but is due to ground-state stabilization through resonance interaction. The positive $\rho$ value suggests that nucleophilic attack by $OH^-$ to form a tetrahedral addition intermediate is the rate-determining step. The large negative ${\Delta}S^\neq$ value determined in the present system is consistent with the proposed mechanism.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1326_1327
• /
• 2009

In this study, used simplest sandwich cells containing $Ru2^+$ liquid electrolytes in order to clarify the role of nanoporous $TiO_2$ electrodes. And, the cell structure is as follow: F:$SnO_2$ glass/nanoporous $TiO_2$/ tris(2,2'-bipyridy)ruthenium(II) colplex [$Ru(bpy)_3(PF_6)_2$] in acetonitrile/ F:$SnO_2$ glass. The result, we found that ECL intensities increased rapidly by use of cathodes with nanoporous $TiO_2$ layers. And, porous $TiO_2$ electrodes were confirmed to be efficient for ECL devices as well as solar cell devices. It is thought that the increases in the ECL intensities may be associated with both formation of $Ru^+$ in porous $TiO_2$ electrodes and the process taking place after reduction of $Ru^+$ which occurs in the nanoporous electrodes.

• Journal of the Korean Chemical Society
• /
• v.47 no.6
• /
• pp.547-552
• /
• 2003

Separation and determinations of Co(II) and Ni(II) ions as their 4-(2-pyridylazo)resorcinol(PAR) chelates by reversed-phase capillary high-performance liquid chromatography(RP-CpHPLC) were performed. Among many capillary columns, Vydac C4 column was selected and acetonitrile solution was used as mobile phase. The effect of pH and MeCN concentration(%) on the retention factor, k and peak intensity was examined and discussed. As a results, it was found that 22.5% MeCN and pH 5.60 was adequate as mobile phase for the separation of the two metal ions and determination of Co(II) ion, but the mobile phase condition for Ni(II) ion determination was 22.5% MeCN of pH 7.20. Detection limit(D.L., S/N=3) of Co(II) and Ni(II) ions were $2.0{\times}10{-7}$ M(14.9 ppb) and $1.0{\times}10{-6}$ M(59.2 ppb), respectively.

• Applied Biological Chemistry
• /
• v.38 no.5
• /
• pp.455-462
• /
• 1995

The new six herbicidal N-[(pyrimidin-2-yl)aminocarbonyl]-2-substituted-6-(1-hydroxy-2-fluoroethyl)benzenesulfonamide derivatives(S) were synthesized and rate constants for the hydrolysis of thier in the range of pH $1.0{\sim}10.0$ have been studied in 15%(v/v) aqueous acetonitrile solution at $45^{\circ}C$. From the basis of the results, pH-effect, solvent effect, ortho-substituent effect, thermodynamic parameters(${\Delta}H^{\neq}$ & ${\Delta}S^{\neq}$), pKa constant(4.80), rate equation, analysis of hydrolysis products(2-(1-hydroxy-2-fluoroethyl)benzenesulfonamide & 4,6-dimethoxyaminopyrimidine), it may be concluded that the general acid catalyzed hydrolysis through $A-S_E2$ mechanism and specific acid catalyzed hydrolysis through A-2 type(or $A_{AC}2$) mechanism proceeds via conjugate acid($SH^+$) and tetrahedral intermediate(I) below pH 8.0, whereas, above pH 9.0, the general base catalyzed hydrolysis by water molecules(B) through $(E_1)_{anion}$ mechanism proceeds via conjugate base(CB). In the range between $pH\;7.0{\sim}pH\;9.0$, these two reactions occur competitively.

• Journal of the Korean Chemical Society
• /
• v.58 no.2
• /
• pp.193-197
• /
• 2014

Dibenzo-18-crown-6, dibenzo-21-crown-7 and dihydroxy dibenzo-18-crown-6 were synthesized by Bayer-Villiger oxidation strategy. Dibenzo-18-crown-6 and dibenzo-21-crown-7 could be synthesized through a three-step protocol starting from salicylaldehyde. Salicylaldehyde was reacted with bis-(2-chloroethyl)ether using $K_2CO_3$ in acetonitrile to link the two phenolic groups with the oxyethylene bridge followed by conversion of the formyl group to the hydroxy group via a Baeyer-Villiger reaction and finally linking the two phenolic group with appropriate oxyethylene bridge. The two target crown ethers were obtained in overall yield, 24% and 30%, respectively. This method has a great potential for synthesis of symmetrical as well as unsymmetrical dibenzo crowns with varying oxyethylene bridges. Baeyer-Villiger oxidation could be used to prepare dihydroxy derivative of dibenzo-18-crown-6 through acetylation of dibenzo-18-crown-6 followed by Baeyer-Villiger oxidation. The Baeyer-Villiger oxidation could be substantially accelerated using trifluoroacetic acid.