Asymmetric syntheses of (−)-isoretronecanol and (−)-trachelantamidine

Short and concise total asymmetric syntheses of (−)-isoretronecanol and (−)-trachelantamidine are reported. Oxidative cleavage of tert-butyl (S,S,S,Z)-7-[N-benzyl-N-(α-methylbenzyl)amino]cyclohept-3-ene-1-carboxylate, followed by hydrogenolysis promoted in situ cyclisation/reduction, which provided rapid access to the bicyclic core within (−)-isoretronecanol. Analogous treatment of the C(1)-epimer gave (−)-trachelantamidine. Overall, the syntheses of (−)-isoretronecanol and (−)-trachelantamidine were completed in eight and seven steps and 20 and 9.5% yield, respectively, from commercially available starting materials.     

Reactions of enaminones and related compounds with N,N-dimethylacetamide dimethyl acetal. A simple one-pot metal-free synthesis of polysubstituted benzene derivatives

Herein a simple one-pot metal-free synthesis of alkyl-, aryl-, heteroaryl- and alkoxycarbonyl substituted 1,3-bis(dimethylamino)benzene derivatives is described. The products were prepared from the corresponding methyl ketones or compounds with an α-methylene group in regard to the carbonyl group, using N,N-dimethylacetamide dimethyl acetal (DMADMA) as the reagent.     

Headspace stir bar sorptive extraction followed by thermal desorption and gas chromatography with mass spectrometry to determine musk fragrances in sludge samples without sample pretreatment

A direct, simple and solvent‐free method based on headspace stir bar sorptive extraction and thermal desorption gas chromatography with mass spectroscopy was developed to determine 13 musk fragrances (six polycyclic musks, three nitro musks and four macrocyclic musks) in sludge without sample treatment. The optimal headspace stir bar sorptive extraction conditions were achieved when a polydimethylsiloxane stir bar was exposed for 45 min in the headspace of a 10 mL vial filled with 100 mg of sludge mixed with 0.2 mL of water stirred at 750 rpm at 80°C. The stir bar was then desorbed in the thermal desorption gas chromatography and mass spectrometry system, obtaining limits of detection between 5 and 30 ng/g. The method applicability was tested with sewage sludge from two urban wastewater treatment plants and from a potable water treatment plant. Results showed galaxolide and tonalide to be the most abundant musk fragrances found in wastewater treatment plants with maximal concentrations of 9240 and 7500 ng/g, respectively. Maximum concentration levels between 35 and 635 ng/g were found for musk ketone, musk moskene, traseolide, phantolide and celestolide in this kind of samples. Concentrations below the limits of quantitation of phantolide, galaxolide, tonalide and musk ketone were found in sludge from a potable water treatment plant.     

Validation of a novel method to identify in utero ethanol exposure: simultaneous meconium extraction of fatty acid ethyl esters,ethyl glucuronide,and ethyl sulfate followed by LC-MS/MS quantification

Presence of fatty acid ethyl esters (FAEE), ethyl glucuronide (EtG), and ethyl sulfate (EtS) in meconium, the first neonatal feces, identifies maternal alcohol consumption during pregnancy. Current meconium alcohol marker assays require separate analyses for FAEE and EtG/EtS. We describe development and validation of the first quantitative liquid chromatography tandem mass spectrometry assay for 9 FAEEs, EtG, and EtS in 100 mg meconium. For the first time, these alcohol markers are analyzed in the same meconium aliquot, enabling comparison of the efficiency of gestational ethanol exposure detection. 100 mg meconium was homogenized in methanol and centrifuged. The supernatant was divided, and applied to two different solid phase extraction columns for optimized analyte recovery. Limits of quantification for ethyl laurate, myristate, linolenate, palmitoleate, arachidonate, linoleate, palmitate, oleate, and stearate ranged from 25–50 ng/g, with calibration curves to 2,500–5,000 ng/g. EtG and EtS linear dynamic ranges were 5–1,000 and 2.5–500 ng/g, respectively. Mean bias and between-day imprecision were <15 %. Extraction efficiencies were 51.2–96.5 %. Matrix effects ranged from ?84.7 to 16.0 %, but were compensated for by matched deuterated internal standards when available. All analytes were stable (within ±20 % change from baseline) in 3 authentic positive specimens, analyzed in triplicate, after 3 freeze/thaw cycles (?20 °C). Authentic EtG and EtS also were stable after 12 h at room temperature and 72 h at 4 °C; some FAEE showed instability under these conditions, although there was large inter-subject variability. This novel method accurately detects multiple alcohol meconium markers and enables comparison of markers for maternal alcohol consumption.

A novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry based on sample mixing with a non-enriched standard

In this work, a novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry (MC-ICP-MS) for low amounts of target element is proposed. The methodology is based on mixing of the sample (target element isolate) with a non-enriched in-house standard, previously characterized for its isotopic composition. This methodology has been applied to isotopic analysis of Cu and of Fe in whole blood samples. For this purpose, different mixtures of sample + in-house standard were prepared and adjusted to a final concentration of 500 μg/L of the target elements for isotopic analysis. δ⁶⁵Cu, δ⁵⁶Fe, and δ⁵⁷Fe varied linearly as a function of the amount of in-house standard (or of sample) present in the mixture. The isotopic composition of the sample was calculated considering the isotope ratios measured for (i) the mixture and (ii) the in-house standard and (iii) the relative concentrations of target element contributed by the sample and the standard to the mixture, respectively. For validation purposes, the isotopic analysis of whole blood Cu was carried out using both the conventional (using 2 mL of whole blood) and the newly developed approach (using 500 μL of whole blood). The δ⁶⁵Cu values obtained using mixtures containing 40 % (200 μg/L) of Cu from the blood samples and 60 % (300 μg/L) of Cu from the in-house standard were in good agreement with the δ⁶⁵Cu value obtained using the conventional approach (bias ≤0.15?‰).     

A validated stability-indicating LC method for simultaneous determination of quinapril and hydrochlorothiazide in pharmaceutical samples

A stability-indicating liquid chromatographic method was developed and validated for simultaneous determination of quinapril and hydrochlorothiazide in drug substances and dosage forms. Chromatographic separation of quinapril, hydrochlorothiazide and its degradation products was achieved on a RP-18 column, using acetonitrile and phosphate buffer (pH 4.6) as mobile phase in a gradient mode and detection at 216 nm. Stress testing was performed under hydrolytic, oxidative, thermal and photolytic conditions. The degradation products were well resolved from main peaks, proving the stability-indicating power of the method. The assay was linear for quinapril and hydrochlorothiazide concentrations of 40–200 µg mL^?1 and 25–125 µg mL^?1, respectively. The developed method was selective, accurate and precise for quinapril and hydrochlorothiazide determination. This method was used to quantify both drugs in combined commercial tablets. The results showed that the proposed method was found to be suitable for quantitative determination and the stability study of quinapril and hydrochlorothiazide in pharmaceutical samples.      

Tacrines as Therapeutic Agents for Alzheimer's Disease. V. Recent Developments

Herein we have reviewed our recent developments for the identification of new tacrine analogues for Alzheimer's disease (AD) therapy. Tacrine, the first cholinesterase inhibitor approved for AD treatment, did not stop the progression of AD, producing only some cognitive improvements, but exhibited secondary effects mainly due to its hepatotoxicity. Thus, the drug was withdrawn from the clinics administration. Since then, many publications have described non‐hepatotoxic tacrines, and in addition, important efforts have been made to design multitarget tacrines by combining their cholinesterase inhibition profile with the modulation of other biological targets involved in AD.     

Two Ecdysteroids Isolated from Micropropagated Lychnis flos-cuculi and the Biological Activity of Plant Material

Genetically uniform plant material, derived from Lychnis flos-cuculi propagated in vitro, was used for the isolation of 20-hydroxyecdysone and polypodine B and subjected to an evaluation of the antifungal and antiamoebic activity. The activity of 80% aqueous methanolic extracts, their fractions, and isolated ecdysteroids were studied against pathogenic Acanthamoeba castellani. Additionally, a Microtox^® acute toxicity assay was performed. It was found that an 80% methanolic fraction of root extract exerts the most potent amoebicidal activity at IC₅₀ of 0.06 mg/mL at the 3rd day of treatment. Both ecdysteroids show comparable activity at IC₅₀ of 0.07 mg/mL. The acute toxicity of 80% fractions at similar concentrations is significantly higher than that of 40% fractions. Crude extracts exhibited moderate antifungal activity, with a minimum inhibitory concentration (MIC) within the range of 1.25–2.5 mg/mL. To the best of our knowledge, the present report is the first to show the biological activity of L. flos-cuculi in terms of the antifungal and antiamoebic activities and acute toxicity. It is also the first isolation of the main ecdysteroids from L. flos-cuculi micropropagated, ecdysteroid-rich plant material.     

Diagnosis of suspicious breast lesions using an empirical mathematical model for dynamic contrast-enhanced MRI

The purpose of this study was to test whether an empirical mathematical model (EMM) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can distinguish between benign and malignant breast lesions. A modified clinical protocol was used to improve the sampling of contrast medium uptake and washout. T(1)-weighted DCE magnetic resonance images were acquired at 1.5 T for 22 patients before and after injection of Gd-DTPA. Contrast medium concentration as a function of time was calculated over a small region of interest containing the most rapidly enhancing pixels. Then the curves were fitted with the EMM, which accurately described contrast agent uptake and washout. Results demonstrate that benign lesions had uptake (P<2.0 x 10(-5)) and washout (P<.01) rates of contrast agent significantly slower than those of malignant lesions. In addition, secondary diagnostic parameters, such as time to peak of enhancement, enhancement slope at the peak and curvature at the peak of enhancement, were derived mathematically from the EMM and expressed in terms of primary parameters. These diagnostic parameters also effectively differentiated benign from malignant lesions (P<.03). Conventional analysis of contrast medium dynamics, using a subjective classification of contrast medium kinetics in lesions as "washout," "plateau" or "persistent" (sensitivity=83%, specificity=50% and diagnostic accuracy=72%), was less effective than the EMM (sensitivity=100%, specificity=83% and diagnostic accuracy=94%) for the separation of benign and malignant lesions. In summary, the present research suggests that the EMM is a promising alternative method for evaluating DCE-MRI data with improved diagnostic accuracy.