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1.
Use of proton nuclear magnetic resonance spectroscopy and the lanthanide shift reagent, Eu(hfc)3, resulted in a simple and reliable method for determination of the diastereomeric purity of trans-2-phenylcyclopropylamine sulfate (tranylcypromine sulfate). Eu(hfc)3 effectively simplified the complex overlapping pattern of the 5 non-equivalent phenyl protons to a virtually first order pattern. At a shift reagent to substrate molar ratio of 0.75, and a substrate concentration of 0.25M (as the free base) in CDCl3, the resonances for the cis- and trans-ortho-phenyl protons at 11.39 and 9.99 ppm, respectively, were sufficiently resolved to be of use in quantitative work. Analysis of synthetic diastereomeric mixtures of 2-phenylcyclopropylamine sulfate by the proposed method yielded results that were in close agreement with the expected values. The mean recovery (SD) of trans-diastereomer was 100.51% (0.40) (n = 6). Levels of less than 2% of cis-diastereomer were measurable in cis-trans mixtures.  相似文献   

2.
Using 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) as substrate, it has been shown that the increased peroxidase activity for decreasing pH of myoglobin activated by hydrogen peroxide is due to a protonization of ferrylmyoglobin, MbFe(IV)=O, facilitating electron transfer from the substrate and corresponding to pK(a) approximately 5.2 at 25.0 degrees C and ionic strength 0.16, rather than due to specific acid catalysis. On the basis of stopped flow absorption spectroscopy with detection of the radical cation ABTS(.+), the second-order rate constant and activation parameters for the reaction between MbFe(IV)=O and ABTS were found to have the values k = 698 +/- 32 M(-1) s(-1), DeltaH# = 66 +/- 4 kJ mol(-1), and DeltaS# = 30 +/- 15 J mol(-1) K(-1) at 25.0 degrees C and physiological pH (7.4) and ionic strength (= 0.16 M NaCl). At a lower pH (5.8) corresponding to the conditions in meat, values were found as follows: k = 3.5 +/- 0.3 x 10(4) M(-1) s(-1), DeltaH# = 31 +/- 6 kJ mol(-1), and DeltaS# = -53 +/- 19 J mol(-1) K(-1), indicative of a shift from outersphere electron transfer to an innersphere mechanism. For steady state assay conditions, this shift is paralleled by a shift from saturation kinetics at pH 7.4 to first-order kinetics for H2O2 as substrate at pH 5.8. In contrast, the activation reaction between myoglobin and hydrogen peroxide was found at 25.0 degrees C to be slow and independent of pH with values of 171 +/- 7 and 196 +/- 19 M(-1) s(-1) found at physiological and meat pH, respectively, as determined by sequential stopped flow spectroscopy, from which a lower limit of k = 6 x 10(5) M(-1) s(-1) for the reaction between perferrylmyoglobin, .MbFe(IV)=O, and ABTS could be estimated. As compared to the traditional peroxidase assay, a better characterization of pseudoperoxidase activity of heme pigments and their denatured or proteolyzed forms is thus becoming possible, and specific kinetic effects on activation, substrate oxidation, or shift in rate determining steps may be detected.  相似文献   

3.
The objective of the present study was to determine the degradation products of mancozeb and ethylenethiourea (ETU) and elucidate the possible degradation pathways in solution as a result of chemical oxidation using ozone and chlorine dioxide. This study was developed in a solution at 100 ppm of mancozeb and ETU concentration over the course of 60 min. Two different oxidizing agents used in this study were (1) ozone at 3 ppm and (2) chlorine dioxide at 20 ppm. Ozone was continuously provided throughout the course of the reaction. Degradation products were detected with high-resolution GC-MS. The total analysis time was 4 min per sample combined with rapid GC separation and time-of-flight mass spectrometry (TOFMS). Hydrolysis of mancozeb led to m/z 144 ion fragmentation, which is 5-imidazoledithiocarboxylic acid, as a major degradation product. ETU showed M(+) 102, which corresponds to its mass, indicating this compound was stable in distilled water and did not undergo hydrolysis during 60 min. The average retention times of mancozeb and ETU were approximately 181-189 and 210-230 s, respectively. Ozonation of mancozeb produced ETU as a major product. Treatment of ETU with ozone produced several degradation compounds. From prolonged ozonation, the CS(2) or CS group was removed. Overall, several byproducts identified were M(+) 60, M(+) 84, M(+) 163, M(+) 117, and M(+) 267 by ozone and M(+) 117, M(+) 86, and M(+) 163 by chlorine dioxide treatment. Several of these have been reported, but others have never been reported previously.  相似文献   

4.
(S)-(+)-O-methylmandelate esters of trans- and cis-1,3, 3-trimethyl-2-oxabicyclo[2.2.2]octan-5- and 6-ols (2- and 3-hydroxy-1,8-cineoles) were prepared, and eight diastereomers were separated. The absolute configuration of the asymmetric carbons of the cineole moiety of each diastereomer was determined by (1)H NMR data according to the Mosher theory. Each mandelate was reduced with LiAlH(4) to obtain optically pure hydroxy-1,8-cineoles, this being followed by acetylation to afford optically pure acetoxy-1, 8-cineoles. These acetates were subjected to chiral GC, using a cyclodextrin column, and the enantiomeric purity of trans- and cis-1, 3,3-trimethyl-2-oxabicyclo[2.2.2]octan-5- and 6-yl acetates in the aroma concentrate from the rhizomes of Alpinia galanga was determined as 93.9 (5S), 19.4 (5R), 63.5 (6R), and 100 (6R) % ee, respectively. The aroma character of each enantiomer was also evaluated by GC-sniffing.  相似文献   

5.
The polyphenol oxidase from field bean (Dolichos lablab) seeds has been purified to apparent homogeneity by a combination of ammonium sulfate precipitation, DEAE-Sephacel chromatography, phenyl agarose chromatography, and Sephadex G-200 gel filtration. The purified enzyme has a molecular weight of 120 +/- 3 kDa and is a tetramer of 30 +/- 1.5 kDa. Native polyacrylamide gel electrophoresis of the purified enzyme revealed the presence of a single isoform with an observed pH optimum of 4.0. 4-Methyl catechol is the best substrate, followed by catechol, and L-3,4-dihydroxyphenylalanine, all of which exhibited a phenomenon of inhibition by excess substrate. No activity was detected toward chlorogenic acid, catechin, caffeic acid, gallic acid, and monophenols. Tropolone, both a substrate analogue and metal chelator, proved to be the most effective competitive inhibitor with an apparent K(i) of 5.8 x 10(-)(7) M. Ascorbic acid, metabisulfite, and cysteine were also competitive inhibitors.  相似文献   

6.
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7.
A celulose tris(3,5-dimethylphenylcarbamate) coated onto APS silica (Nucleosil, particle size, 7 microm; pore size, 500 A) was used under a reversed-phase condition to measure the enantiomeric ratios of gossypol enantiomers in cottonseeds, flowers, and roots in a number of cultivars samples of different Gossipium species. While unidimensional chromatography was used for measuring the enantiomeric ratio of all the samples of G. hirsutum, G. mustelinum, and in the seeds of G. barbadense, multidimensional chromatography was necessary for the analysis of samples of roots and flowers of G. barbadense. In the latter case, an ODS Hypersil column was used in the first dimension for sample clean up, and the enantiomers were resolved on the second dimension by the chiral column. As expected, all the seed samples of G. hirsutum and G. mustelinum showed the (P)-(+)-enantiomer in excess, whereas the seeds of G. barbadense showed the (M)-(-)-enantiomer. However, (P)-(+)-gossypol was found in enantiomeric excess in three samples examined of roots and in one of flower of G. barbadense. These results are discussed in this paper.  相似文献   

8.
Evening primrose meal (EPM: 1% and 2%, w/w) reduced (p 相似文献   

9.
Different monosulfates of quercetin and epicatechin with metabolic interest were obtained by hemisynthesis and characterized regarding their chromatographic behavior and absorption and mass spectra. Three of these compounds were further isolated, and their structures were elucidated by mass spectrometry and (1)H and (13)C nuclear magnetic resonance using one- and two-dimensional techniques (heteronuclear single-quantum coherence and heteronuclear multiple-bond correlation). The calculation of the proton and carbon shifts caused by sulfation allowed for the assignment of the position of the sulfate group in the flavonoids, so that the compounds were identified as quercetin-3'-O-sulfate, quercetin 4'-O-sulfate, and epicatechin 4'-O-sulfate. It was found that sulfation at position 3' induced a large upfield shift in the carbon bearing the sulfate group and downfield displacements of the adjacent carbons, whereas no significant upfield or downfield shifts were observed with respect to the parent flavonoid when sulfation was produced at position 4'.  相似文献   

10.
An analytical method for detecting cymoxanil [2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino)acetamide] residues in dried hops was developed utilizing liquid-liquid partitioning, automated gel permeation chromatography (GPC), solid phase extraction (SPE) cleanup, and gas chromatography (GC). Method validation recoveries from dried hops were 96 +/- 12, 108 +/- 11, and 136 +/- 8% over three levels of fortification (0.05, 0.5, and 1.0 ppm, respectively). The hop samples from three field sites, which were treated with cymoxanil, had residue levels ranging from 0.146 to 0.646 ppm. The detection limit and the quantitation limit of the method developed in the present study were 0.022 and 0.050 ppm, respectively.  相似文献   

11.
Gossypol is an allelochemical that occurs naturally throughout the cotton plant as an enantiomeric mixture. Gossypol and related terpenoids protect the plant from some insect herbivores. Cottonseed has a high protein content, but it is underutilized because (-)-gossypol, which is toxic to nonruminants, occurs in the seed along with (+)-gossypol. Commercial Upland cottons usually have an approximate 3:2 (+)- to (-)-gossypol ratio in the seed, but plants can be bred with <8% (-)-gossypol using accessions of Gossypium hirsutum var. marie galante as parents. We report the (+)- and (-)-gossypol ratios and the concentration of related terpenoids in the stems, leaves, and roots of four accessions of marie galante that show high, moderate, and near normal levels of (+)-gossypol in the seed; we compare these values to the commercial cultivar Stoneville 474, which has 62% (+)-gossypol in the seed. In the marie galante accessions 2452 and 2425 that have the highest levels of (+)-gossypol in the seed, the percent (+)-gossypol and the concentration of gossypol and the related terpenoids were significantly higher (P = 0.05) in the stems and leaves as compared to Stoneville 474. Our analysis indicates that progeny from accessions 2452 and 2425 that retain these traits should not be overly susceptible to herbivorous insects.  相似文献   

12.
Liquid chromatographic determination of acifluorfen in soil and water   总被引：1，自引：0，他引：1  
An analytical method based on the use of a liquid chromatograph equipped with a UV detector was developed for the determination of acifluorfen in soil and water. Acifluorfen was extracted from soil in methanol-0.10N NaOH (80 + 20 v/v) and from water by partition with dichloromethane. Solvent partitioning and solid-phase extraction were used to separate acifluorfen from major interfering sample components. Average recoveries from soil at 1, 0.1, and 0.01 ppm fortification levels were 95.1 +/- 3.4, 92.6 +/- 2.9, and 73.9 +/- 3.0%, respectively. Recoveries from water spiked at levels from 0.01 to 1 ppm averaged 96.5 +/- 5.4%. Method limits of detection were 0.006 ppm in soil and 0.003 ppm in water.  相似文献   

13.
The major in vivo metabolites of (S)-(-)-pulegone in humans using a metabolism of ingestion-correlated amounts (MICA) experiment were newly identified as 2-(2-hydroxy-1-methylethyl)-5-methylcyclohexanone (8-hydroxymenthone, M1), 3-hydroxy-3-methyl-6-(1-methylethyl)cyclohexanone (1-hydroxymenthone, M2), 3-methyl-6-(1-methylethyl)cyclohexanol (menthol), and E-2-(2-hydroxy-1-methylethylidene)-5-methylcyclohexanone (10-hydroxypulegone, M4) on the basis of mass spectrometric analysis in combination with syntheses and NMR experiments. Minor metabolites were be identified as 3-methyl-6-(1-methylethyl)-2-cyclohexenone (piperitone, M5) and alpha,alpha,4-trimethyl-1-cyclohexene-1-methanol (3-p-menthen-8-ol, M6). Menthofuran was not a major metabolite of pulegone and is most probably an artifact formed during workup from known (M4) and/or unknown precursors. The differences in toxicity between (S)-(-)- and (R)-(+)-pulegone can be explained by the strongly diminished ability for enzymatic reduction of the double bond in (R)-(+)-pulegone. This might lead to further oxidative metabolism of 10-hydroxypulegone (M4) and the formation of further currently undetected metabolites that might account for the observed hepatotoxic and pneumotoxic activity in humans.  相似文献   

14.
Monascus purpureus NTU 601 is a strain that produces monacolin K, gamma-aminobutyric acid (GABA), and citrinin under solid culture conditions. Because citrinin is a mycotoxin and possesses nephrotoxic and hepatoxic effects, it has a negative impact on the acceptance of red mold rice by people. In this research, a simple and quick selection method for mutant strains with low citrinin production was designed based on the fact that citrinin possesses antibacterial activity for Bacillus subtilis and will form an inhibition zone around the colony of the Monascus strain. The mutant strain M. purpureus N 301 only produced 0.23 +/- 0.01 ppm citrinin, which was 50% less than that of the parent strain, and the monacolin K production was 481.29 +/- 7.98 ppm and maintained 91% productivity. M. purpureus N 310, the other mutant strain, produced 0.27 +/- 0.01 ppm citrinin, which was 41% less than that of the parent strain, and the monacolin K production was 526.29 +/- 5.54 ppm, which showed no significant changes when compared with the parent strain. The GABA content of the two strains was 5000 ppm, which is similar to that of the parent strain. The results showed that the method could be used to select red mold rice with low citrinin production.  相似文献   

15.
Recently, 3-O-octanoyl-(+)-catechin (OC) was synthesized from (+)-catechin (C) by incorporation of an octanoyl chain into C in the light of (-)-epicatechin gallate (ECg) and (-)-epigallocatechin gallate (EGCg), which are the major polyphenols found in green tea and have strong physiological activities. OC was found to inhibit the response of ionotropic gamma-aminobutyric acid (GABA) receptors (GABA(A) receptors) and Na+/glucose cotransporters expressed in Xenopus oocytes in a noncompetitive manner more strongly than does C. OC also induced a nonspecific membrane current and decreased the membrane potential of the oocyte, and thus death of the oocyte occurred even at lower concentrations than that induced by C or EGCg. Although EGCg produced H2O2 in aqueous solution, OC did not. This newly synthesized catechin derivative OC possibly binds to the lipid membrane more strongly than does C, Ecg, or EGCg and as a result perturbs the membrane structure.  相似文献   

16.
(+)-Catechin reaction with two aldehydes (acetaldehyde and glyoxylic acid) was studied in winelike model solution. The two aldehydes were reacted either individually or together with (+)-catechin and in molar excess. The reactions were followed by HLPC-UV and HPLC-ESI/MS to monitor (+)-catechin disappearance as well as dimer and polymer appearance. In all reactions a reaction order of close to 1 for (+)-catechin disappearance was observed. (+)-Catechin disappearance was slower in the presence of acetaldehyde (t(1/2) = 6.7 +/- 0.2 h) compared to glyoxylic acid (t(1/2) = 2.3 +/- 0.2 h). When the two aldehydes were reacted together, (+)-catechin disappearance was faster (t(1/2) = 2.2 +/- 0.5 h). When aldehydes were reacted separately, the dimer appearance was independent of the type of aldehyde used but the ethyl-bridged dimer disappearance was slower with acetaldehyde. When aldehydes were reacted together, the dimer appearance changed. Ethyl-bridged dimers appeared before carboxymethine-bridged dimers, and their disappearance occurred earlier. Copolymers containing both ethyl and carboxymethine bridges were also observed.  相似文献   

17.
A method was validated for analysis of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) in fortified salmon muscle tissue. Recoveries of OTC were 100 +/- 6, 86 +/- 6, and 82 +/- 5% (n = 6) at fortification levels of 1.0, 0.5, and 0.2 ppm, respectively. Recoveries of TC were 68 +/- 4, 65 +/- 6, and 66 +/- 7%; recoveries of CTC were 45 +/- 9, 48 +/- 8, and 0%, respectively. Detection limits for OTC and TC were 0.08 and 0.09 ppm, respectively.  相似文献   

18.
Methoxyfenozide [3-methoxy-2-methylbenzoic acid 2-(3,5-dimethylbenzoyl)-2-(1,1-dimethylethyl) hydrazide; RH-2485], in the formulation of INTREPID, was applied to various crops. Analysis of methoxyfenozide was accomplished by utilizing liquid-liquid extraction and partitioning, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Method validations for fruits, vegetables, and mint are reported. Methoxyfenozide mean recoveries ranged from 72 to 129% over three levels of fortification. The overall average of mean recoveries is 97 +/- 10%. The limit of quantitation for fruits, artichoke, cucumber, squash, and refined sugar was 0.010 ppm, with a detection limit of 0.005 ppm. For all other crops, the limit of quantitation was 0.050 ppm, with a detection limit of 0.025 ppm. No residues were found greater than the limit of quantitation in control samples. Residues above the limit of quantitation were found in all matrices except refined sugar. Foliage (bean, beet, pea, and radish) had greater residue levels of methoxyfenozide residue than their corresponding roots or pods. Other crop matrices contained <1.0 ppm of methoxyfenozide except artichoke, which had a mean of 1.10 ppm.  相似文献   

19.
Starting from (R)-(+)- and (S)-(-)-pulegone, enantiomeric pairs of esters and lactones with the p-menthane system were obtained. The Claisen rearrangement of allylic alcohols and iodolactonization of gamma,delta-unsaturated acids were the key steps of syntheses presented. The structures of compounds were determined by both spectroscopic and crystallographic methods. Some of the synthesized compounds are characterized by interesting odoriferous properties.  相似文献   

20.
This study presents the phenolic compounds profile of commercial Cornicabra virgin olive oils from five successive crop seasons (1995/1996 to 1999/2000; n = 97), determined by solid phase extraction reversed phase high-performance liquid chromatography (SPE RP-HPLC), and its relationship with oxidative stability, processing conditions, and a preliminary study on variety classification. The median of total phenols content was 38 ppm (as syringic acid), although a wide range was observed, from 11 to 76 ppm. The main phenols found were the dialdehydic form of elenolic acid linked to tyrosol (p-HPEA-EDA; 9 +/- 7 ppm, as median and interquartile range), oleuropein aglycon (8 +/- 6 ppm), and the dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA; 5 +/- 8 ppm). In many cases the correlation with oxidative stability was higher when the sum of the dialdehydic form of elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA) and oleuropein aglycon (r (2) = 0.91-0.96) or the sum of these two and hydroxytyrosol (r (2) = 0.90-0.97) was considered than was observed with HPLC total phenols (r (2)= 0.91-0.95) and especially with colorimetric determination of total polyphenols and o-diphenols (r (2) = 0.77-0.95 and 0.78-0.92, respectively). 3,4-DHPEA-EDA, p-HPEA-EDA, the aglycons of oleuropein and ligstroside, and HPLC total phenols content presented highly significant differences (p = 0.001-0.010) with respect to the dual- and triple-phase extraction systems used, whereas colorimetric total polyphenols content did not (p = 0.348) and o-diphenols showed a much lower significant difference (p = 0.031). The five variables that most satisfactorily classified the principal commercial Spanish virgin olive oil varieties were 1-acetoxypinoresinol, 4-(acetoxyethyl)-1,2-dihydroxybenzene (3,4-DHPEA-AC), ligstroside aglycon, p-HPEA-EDA, and RT 43.3 contents.  相似文献   

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