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HPLC Chromatograms (hplc + chromatogram)
Selected AbstractsInvestigation of cis/trans ratios of peptide bonds in AVP analogues containing N -methylphenylalanine enantiomersJOURNAL OF PEPTIDE SCIENCE, Issue 1 2006Emilia Sikorska Abstract The solution conformation of vasopressin analogues, modified at positions 2 and 3 with N -methylphenylalanine or its enantiomer, [D -MePhe2,MePhe3]AVP and [MePhe2,D -MePhe3]AVP, were studied by 2D NMR spectroscopy in H2O/D2O and theoretical calculations (EDMC/ANALYZE). In the case of [MePhe2,D -MePhe3]AVP, the synthesis afforded two products, A and B, which had identical molecular ions and similar retention times on HPLC. This finding was explained by racemization of Cys1, which gave an additional analogue, [D -Cys1,MePhe2,D -MePhe3]AVP (B). The possibility is not excluded of racemization of Cys1 in the remaining analogues of this series. However, only in the case of [MePhe2,D -MePhe3]AVP was this process so distinct that two strong peaks in the HPLC chromatogram were observed. The NMR spectra of all the analogues showed several distinct sets of residual proton resonances. This suggests that the peptides adopt more than two groups of conformations in H2O/D2O. This fact is due to cis/trans isomerization. Two more populated isomers arise from the cis/trans isomerization across the 2,3 peptide bond in [D -MePhe2,MePhe3]AVP and [MePhe2,D -MePhe3]AVP (A) and across the 1,2 peptide bond in [D -Cys1,MePhe2,D -MePhe3]AVP (B). Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source] Clinical evaluation of spermatogenic activity of processed Shilajit in oligospermiaANDROLOGIA, Issue 1 2010T. K. Biswas Summary The safety and spermatogenic activity of processed Shilajit (PS) were evaluated in oligospermic patients. Initially, 60 infertile male patients were assessed and those having total sperm counts below 20 million ml,1 semen were considered oligospermic and enrolled in the study (n = 35). PS capsule (100 mg) was administered twice daily after major meals for 90 days. Total semenogram and serum testosterone, luteinising hormone and follicle-stimulating hormone were estimated before and at the end of the treatment. Malondialdehyde (MDA), a marker for oxidative stress, content of semen and biochemical parameters for safety were also evaluated. Twenty-eight patients who completed the treatment showed significant (P < 0.001) improvement in spermia (+37.6%), total sperm count (+61.4%), motility (12.4,17.4% after different time intervals), normal sperm count (+18.9%) with concomitant decrease in pus and epithelial cell count compared with baseline value. Significant decrease of semen MDA content (,18.7%) was observed. Moreover, serum testosterone (+23.5%; P < 0.001) and FSH (+9.4%; P < 0.05) levels significantly increased. HPLC chromatogram revealed inclusion of PS constituents in semen. Unaltered hepatic and renal profiles of patients indicated that PS was safe at the given dose. The present findings provide further evidence of the spermatogenic nature of Shilajit, as attributed in Ayurvedic medicine, particularly when administered as PS. [source] Identification of flurbiprofen and its photoproducts in methanol by gas chromatography,mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 5 2007Su-Hui Chao Abstract A sample of 10 mm flurbiprofen in methanol (or ethanol) was photoirradiated with sixteen 8 W low-pressure quartz mercury lamps irradiated at 306 nm in a Panchum PR-2000 photochemical reactor. In total, four major photoproducts derived from each sample were observed from the HPLC chromatogram. The photoproducts were separated and their structures elucidated by various spectroscopic methods. Alternatively, using GC-MS, 11 major photoproducts were observed. A reaction scheme of flurbiprofen in methanol is proposed: the photochemical reaction routes occur mainly via esterification and decarboxylation, followed by oxidation with singlet oxygen to produce a ketone, alcohols and other derivatives. Copyright © 2007 John Wiley & Sons, Ltd. [source] Comparative analysis of triacylglycerols from Olea europaea L. fruits using HPLC and MALDI-TOFMSEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2010Faouzi Sakouhi Abstract MALDI-TOFMS and HPLC are two analytical methods that were used to characterize triacylglycerols (TAG) of the Meski, Sayali, and Picholine Tunisian olive varieties. The HPLC chromatograms of the oils showed the presence of 15 TAG species, among which triolein (OOO) was the most abundant (21,48%). In the Sayali cultivar, OOO was the predominant TAG species followed by POO and LOO. However, the minor TAG molecules were represented by LnLO and LnLP. MALDI mass spectra produced sodiated ([M,+,Na]+) and potassiated ([M,+,K]+) TAG molecules; only the major TAG were potassiated [OOO,+,K] ([OOO,+,K]+, [POO,+,K]+, and [LOO,+,K]+). In contrast to the HPLC chromatograms, the MALDI mass spectra showed 13 peaks of TAG. The major peak was detected at m/z,907, which corresponds to OOO with an Na+ adduct. The results from both HPLC and MALDI techniques predict the fatty acid composition and their percentages for each olive variety. Practical applications: TAG are the main components in vegetable oils. These biomolecules determine the physical, chemical, and nutritional properties of the oils. The nutritional benefits of TAG are related to DAG (moderate plasma lipid level) and esterified FA, which are intermediate biosynthetic molecules of TAG. TAG analysis is necessary to discriminate between oils of different origin, since some oils have similar FA profiles. Olive products, oils, and table olives, are the main diet sources of TAG in the Mediterranean countries. In this work, chromatographic and spectrometric methods were used for TAG analysis and characterization of Tunisian olive varieties. [source] Identification of Trichoderma strains by image analysis of HPLC chromatogramsFEMS MICROBIOLOGY LETTERS, Issue 2 2001Ulf Thrane Abstract Forty-four Trichoderma strains from water-damaged building materials or indoor dust were classified with chromatographic image analysis on full chromatographic matrices obtained by high performance liquid chromatography with UV detection of culture extracts. The classes were compared with morphological identification and rDNA sequence data, and for each class all strains were of the same identity. With all three techniques each strain , except one , was identified as the same species. These strains belonged to Trichoderma atroviride (nine strains), Trichoderma viride (three strains), Trichoderma harzianum (10 strains), Trichoderma citrinoviride (12 strains), and Trichoderma longibrachiatum (nine strains). The odd strain was identified as Trichoderma hamatum by morphology and rDNA sequencing, but not by image analysis as no reference strains of this species were included. It is concluded that the secondary metabolite profile contains sufficient information for classification and species identification. [source] Dediazoniation of 1-naphthalenediazonium tetrafluoroborate in aqueous acid and in micellar solutionsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2008Carlos Bravo-Diaz We have measured the rates and product yields of dediazoniation of 1-naphthalenediazonium (1ND) tetrafluoroborate in the presence and absence of sodium dodecyl sulfate (SDS) micellar aggregates by employing a combination of UV,vis spectroscopy and high-performance liquid chromatography (HPLC) measurements. Kinetic data were obtained by a derivatization procedure with product yields were determined by HPLC. HPLC chromatograms show that in aqueous acid and in micellar solutions only one dediazoniation product is formed in significant quantities, 1-naphthol (NOH), and the observed rate constants (kobs) are the same when 1ND loss is monitored spectrometrically and when NOH formation is monitored by HPLC. Activation parameters were obtained both in the presence and absence of SDS micellar aggregates. In both the systems, the enthalpies of activation are high and the entropies of activation are positive. The enthalpy of activation in the absence of SDS is very similar to that in the presence of SDS micelles, but the entropy of activation is lower by a factor of 4. As a consequence, SDS micelles speed up the thermal decomposition of 1ND and increase kobs by a factor of 1.5 when [SDS] = 0.02 M. In contrast, results obtained in the presence of complexing systems such as crown ethers and polyethers show significant stabilization of the parent arenediazonium ions. Kinetic and HPLC data are consistent with the heterolytic DN + AN mechanism that involves the rate-determining fragmentation of the arenediazonium ion into a very reactive phenyl cation that reacts competitively with available nucleophiles. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 301,309, 2008 [source] Oxidative Degradation of Bisphenol A by Fruit HomogenatesJOURNAL OF FOOD SCIENCE, Issue 9 2005Masaaki Imanaka ABSTRACT: The oxidative degradation of bisphenol A (BPA) by several fruit homogenates was investigated. Their homogenates were incubated with BPA at 25 °C for 0 to 120 min, and the acetone extracts were analyzed by high-performance liquid chromatography (HPLC) with a photodiode array detector (200 to 650 nm). The 2 degradation products (UK-1 and UK-2) from BPA were detected on HPLC chromatograms (280 nm). UK-1 and UK-2 were identified to be 2-(3,4-dihydroxyphenyl)-2-(4-ydroxyphenyl) propane, (3-OH-BPA) and 4-[1-(3,4-dihydroxyphenyl)-isopropyl]benzene-1,2-diol, (3,3,-diOH-BPA), respectively, by HPLC-MassPectrometry (LC-MS). In the process of incubation, the peak of 3-OH-BPA attained the maximum value in the 1st 20 min, and that of 3,3,-diOH-BPA increased more slowly, attaining the maximum in 50 min. On the other hand, incubation of 3-OH-BPA (instead of BPA) with grape homogenates gave the maximum peak of 3,3,-diOH-BPA in only 10 min. 3, 3,-diOH-BPA was a polyphenol compound that contained 4 hydroxyl groups. These results suggested that BPA would be degraded (converted) to brown pigments through the compounds of 3-OH-BPA and 3, 3,-diOH-BPA in some fruit homogenates. [source] Determination of the 2,3-pentadienedioic acid enantiomer interconversion energy barrier 1.JOURNAL OF SEPARATION SCIENCE, JSS, Issue 15 2006Classical kinetic approach Abstract A classical kinetic method was used to determine the energy barrier for the interconversion of 2,3-pentadienedioic acid enantiomers. Each individual enantiomer was isolated by collecting the appropriate peaks from the HPLC enantiomeric separation, of racemic 2,3-pentadienedioic acid. The isolated enantiomers were racemized at 22°C using various interconversion times. The ratio of enantiomers in each reaction solution was determined by HPLC at 22°C. The corresponding peak areas of the enantiomers and the interconversion times obtained from the HPLC chromatograms were used to calculate both the interconversion rate constants describing (+) , (,) and (,) , (+) interconversions as well as the energy barriers. It was confirmed that the interconversion of 2,3-pentadienedioic acid enantiomers is a first-order kinetic reaction. Both semiempirical and ab initio methods were used to explore the mechanism of the interconversion of 2,3-pentadienedioic acid enantiomers, and to calculate the interconversion energy barrier. Comparison of the interconversion energy barriers found by the ab initio method (,G# = 110.7 kJ/mol) and by classical kinetics in the mobile phase solution at 22°C (,Gapp = 93.9 ± 0.2 kJ/mol) shows a difference which may be attributed to the different conditions assumed in the theoretical calculation (i. e., a gaseous state) and the actual experimental conditions (i. e., liquid solution) and a possible catalytic effect of the solution composition. [source] | |||||||||||||