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Phospholipids (1–5 mg) are mixed with methyl heptadecanoate as an internal standard. One part of the sample is reduced with Vitride in tetrahydrofuran in a sealed tube at 50 2C for 1 hr. The reaction products are acetylated in the same tube by treatment with acetic acid-acetic anhydride at 140 °C. After 1 hr total O-acyl and after 16 additional hours glycerol are determined as the fully acetylated compounds by gas-liquid chromatography.Another part of the sample is subjected to acidic hydrolysis and total O-acyl and N-acyl groups are determined by GLC as fatty-acid methyl esters. The aqueous phase is heated to 100 °C with 6 N HCl for 72 hr and phosphorus is measured colorimetrically. 相似文献
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Abstract Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood. 相似文献
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Z.M. Babar Wan Mohd Azizi Solachuddin JA Ichwan Qamar Uddin Ahmed Abul Kalam Azad Imranul Mawa 《Natural product research》2019,33(15):2266-2270
The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems. 相似文献
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Samuel K Yin W Stearns RA Tang YS Chaudhary AG Jewell JP Lanza T Lin LS Hagmann WK Evans DC Kumar S 《Journal of mass spectrometry : JMS》2003,38(2):211-221
Metabolic activation of drug candidates to electrophilic reactive metabolites that can covalently modify cellular macromolecules may result in acute and/or idiosyncratic immune system-mediated toxicities in humans. This presents a significant potential liability for the future development of these compounds as safe therapeutic agents. We present here an example of an approach where sites of metabolic activation within a new drug candidate series were rapidly identified using online liquid chromatography/multi-stage mass spectrometry on an ion trap mass spectrometer. This was accomplished by trapping the reactive intermediates formed upon incubation of compounds with rat and human liver microsomes as their corresponding glutathione conjugates and mass spectral characterization of these thiol adducts. Based on the structures of the GSH adducts identified, potential sites and mechanisms of bioactivation within the chemical structure were proposed. These metabolism studies were interfaced with iterative structural modifications of the chemical series in order to block these bioactivation sites within the molecule. This strategy led to a significant reduction in the propensity of the compounds to undergo metabolic activation as evidenced by reductions in the irreversible binding of radioactivity to liver microsomal material upon incubation of tritium-labeled compounds with this in vitro system. With the efficiency and throughput achievable with such an approach, it appears feasible to identify and address the metabolic activation potential of new drug leads during routine metabolite identification studies in an early drug discovery setting. 相似文献
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Overman LE Larrow JF Stearns BA Vance JM 《Angewandte Chemie (International ed. in English)》2000,39(1):213-215
All three stereoisomers of the hexacyclic 3a,3a'-bispyrrolidino[2,3-b]indoline moiety found in complex indole alkaloids can be prepared, as illustrated by total syntheses of meso-chimonanthine (1) and (+)-chimonanthine (2). A rare example of high diastereoselectivity arising from the combination of a prostereogenic enolate with a chiral electrophile containing a sp(3) carbon atom is the key feature of the asymmetric synthesis of the C(2) stereoisomer. 相似文献
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An experimental study of the thermal decomposition of a β‐hydroxy alkene, 3‐methyl‐3‐buten‐1‐ol, in m‐xylene solution, has been carried out at five different temperatures in the range of 513.15–563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s?1) = (25.65 ± 1.52) ? (17,944 ± 814) (kJ·mol?1)·T?1. A computational study has been carried out at the M05–2X/6–31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811–1816) for the thermal decomposition of 3‐buten‐1‐ol, in m‐xylene solution. We can conclude that in the compound studied in this work, 3‐methyl‐3‐buten‐1‐ol, the effect of substitution at position 3 by a weakly activating CH3 group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition. 相似文献
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We present the spectroscopy and photofragmentation dynamics of two isomeric protonated dipeptides, H+AlaTyr and H+TyrAla, in a cold ion trap. By a combination of infrared-ultraviolet double resonance experiments and density functional theory calculations, we establish the conformations present at low temperature. Interaction of the charge at the N-terminus with the carbonyl group and the tyrosine pi-cloud seems to be critical in stabilizing the low-energy conformations. H+AlaTyr has the flexibility to allow a stronger interaction between the charge and the aromatic ring than in H+TyrAla, and this interaction may be responsible for many of the differences we observe in the former: a significant redshift in the ultraviolet spectrum, a much larger photofragmentation yield, fewer stable conformations, and the absence of fragmentation in excited electronic states. 相似文献