Determination of glycyrrhetinic acid in human plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method has been developed for measuring 18 beta-glycyrrhetinic acid (GRA) in human plasma in the range of 0.1-3 micrograms/ml. The acetate ester of GRA is added to the plasma as an internal standard, plasma proteins are denatured with urea to release GRA, and the GRA and the internal standard are extracted in an ion-pairing solid-phase extraction process. An isocratic, reversed-phase HPLC separation is used, followed by ultraviolet absorbance detection at 248 nm. The results from the analysis of five GRA-fortified plasma pools show a mean relative standard deviation of 7% and are accurate to within 10%. With evaporative concentration of the extract, the limit of detection for GRA in plasma is approximately 10 ng/ml.     

Determination of aflatoxins in grains and raw peanuts by a rapid procedure with fluorometric analysis

A rapid, quantitative, inexpensive, and efficient method was developed to determine aflatoxins in corn, corn meal, popcorn, rice, wheat, cottonseed, and peanuts. Samples are ground and extracted with methanol-water (80 + 20). A portion of the extract is cleaned up by passage through a solid-phase separatory column, 500 microL purified extract is derivatized with a bromine reagent, and fluorescence of the solution is immediately quantified with a calibrated fluorometer containing a broad wavelength pulsed xenon light source. This method can quantify aflatoxin from 5 to 5000 ppb without dilution and was linear when applied to samples of noncontaminated corn spiked at 0 to 5000 micrograms aflatoxin B1/g. Correlation coefficients of the method with LC for multiple analyses for corn (n = 34), cottonseed (n = 32), and peanuts (n = 11) were 0.999, 0.995, and 0.980, respectively. Individual analyses may be conducted in less than 5 min, and grouping of samples is unnecessary. The sensitivity of the method for corn is 5 ppb and the fluorometer, under the operating conditions, has a limit of detection of 0.6 ng aflatoxin B1.     

Chemoenzymatic synthesis of carbasugars from iodobenzene

The versatile enantiopure cis-dihydrodiol metabolite 1, formed by bacterial metabolism of iodobenzene, has been used for the synthesis of the pyranose carbasugars (pseudosugars) carba-beta-D-altropyranose 2, carba-alpha-L-galactopyranose 3, carba-beta-D-idopyranose 4 and carba-beta-L-glucopyranose 5. Substitution of the iodine atom by a carbomethoxy group, stereoselective catalytic hydrogenation of an alpha,beta-unsaturated ester, and regioselective inversion of one or two allylic chiral centres are the key steps used in the synthesis of carbasugars 2-5. The relative and absolute configurations of compounds 2-5 were established by a combination of stereochemical correlation, X-ray crystallography and 1H-NMR spectroscopy.     

Rapid confirmatory analysis of non-steroidal anti-inflammatory drugs in bovine milk by rapid resolution liquid chromatography tandem mass spectrometry

A rapid method has been developed to analyse carprofen (CPF), diclofenac (DCF), mefenamic acid (MFN), niflumic acid (NIFLU), naproxen (NAP), oxyphenylbutazone (OXYPHEN), phenylbutazone (PBZ) and suxibuzone (SUXI) residues in bovine milk. Milk samples are extracted with acetonitrile and sample extracts were purified on Evolute™ ABN solid phase extraction cartridges. Aliquots were analysed by rapid resolution liquid chromatography tandem mass spectrometry (RRLC-MS/MS) with a runtime of 6.5 min. The method was validated in bovine milk, according to the criteria defined in Commission Decision 2002/657/EC. CCα values of 0.46, 1.08, 0.92, 1.26, 1.29, 2.12, 0.55 and 2.86 ng mL⁻¹ were determined for CPF, DCF, MFN, NIFLU, NAP, OXYPHEN, PBZ and SUXI, respectively. CCβ values of 0.79, 1.85, 1.56, 2.15, 2.19, 3.62, 0.94 and 4.87 ng mL⁻¹ were determined for CPF, DCF, MFN, NIFLU, NAP, OXYPHEN, PBZ and SUXI, respectively. The measurement uncertainty of the method was estimated at 9, 28, 28, 45, 46, 45, 10 and 39% for CPF, DCF, MFN, NIFLU, NAP, OXYPHEN, PBZ and SUXI. Fortifying bovine milk samples (n = 18) in three separate assays, show the accuracy of the method to be between 82 and 108%. The precision of the method, expressed as RSD values for the within-lab reproducibility at the three levels of fortification (5, 7.5 and 10 ng mL⁻¹) was less than 16%, respectively. The advantage of the method is that low ng mL⁻¹ levels can be detected and quantitatively confirmed rapidly in milk and that 3 batches of samples can be analysed within a single day using RRLC-MS/MS with a runtime of 6.5 min.     

Absolute configuration assignment and enantiopurity determination of chiral alkaloids and coumarins derived from O- and C-prenyl epoxides

A combination method of ozonolysis and chiral stationary phase (CSP)-GC-MS analysis has been developed to determine the enantiopurity values and absolute configurations of a range of alkaloid and coumarin hemiterpenoids derived from C- and O-prenyl epoxides.     

ZS-metacyclic groups and their endomorphism near-rings

ItG is a group written additively, the inner automorphisms and the endomorphisms additively generate near-ringsI(G) andE(G) respectively. IfI(G)=E(G), i.e., if every endomorphism is a sum of inner automorphisms, we callG anI-E group. In this paper we describe a class ofI-E groups which includes two of the four known classes ofI-E groups and which contains infinitely many other examples. The order ofI(G) is obtained and its radical determined.Supported in part by the Natural Sciences and Engineering Research Council of Canada.     

Ex vivo magnetic resonance imaging of rat spinal cord at 9.4 T

The magnetic resonance (MR) properties of the rat spinal cord were characterized at the T9 level with ex vivo experiments performed at 9.4 T. The inherent endogenous contrast parameters, proton density (PD), longitudinal and transverse relaxation times T1 and T2, and magnetization transfer ratio (MTR) were measured separately for the grey matter (GM) and white matter (WM). Analysis of the measurements indicated that these tissues have statistically different proton densities with means PD(GM)=54.8+/-2.5% versus PD(WM)=45.2+/-2.4%, and different T1 values with means T1GM=2.28+/-0.23 s versus T1WM=1.97+/-0.21 s. The corresponding values for T2 were T2GM=31.8+/-4.9 ms versus T2WM=29.5+/-4.9 ms, and the difference was insignificant. The difference between MTR(GM)=31.2+/-6.1% and MTR(WM)=33.1+/-5.9% was also insignificant. These results collectively suggest that PD and T1 are the two most important parameters that determine the observed contrast on spinal cord images acquired at 9.4 T. Therefore, in MR imaging studies of spinal cord at this field strength, these parameters need to be considered not only in optimizing the protocols but also in signal enhancement strategies involving exogenous contrast agents.     

Transform-Limited Pulses Are Not Optimal for Resonant Multiphoton Transitions

Maximizing nonlinear light-matter interactions is a primary motive for compressing laser pulses to achieve ultrashort transform limited pulses. Here we show how, by appropriately shaping the pulses, resonant multiphoton transitions can be enhanced significantly beyond the level achieved by maximizing the pulse's peak intensity. We demonstrate the counterintuitive nature of this effect with an experiment in a resonant two-photon absorption, in which, by selectively removing certain spectral bands, the peak intensity of the pulse is reduced by a factor of 40, yet the absorption rate is doubled. Furthermore, by suitably designing the spectral phase of the pulse, we increase the absorption rate by a factor of 7.