The use of immobilized capillary enzyme reactors (ICERs) for online ligand screening has been adopted as a new technique for high-throughput screening (HTS). In this work, the selected target was the enzyme acetylcholinesterase (AChE), and the AChE-ICERs produced were used in a liquid chromatograph-tandem ion-trap mass spectrometer. The activity and kinetic parameters were evaluated by monitoring the choline's precursor ion (M + H)(+)m/z 104.0 and its ion fragment (C2H3OH) - (M + H)(+)m/z 60.0. The assay method was validated using the reference AChE inhibitors tacrine and galanthamine. Two new ligands, out of a library of 17 coumarin derivatives, were identified, and the half-maximal inhibitory concentration (IC50), inhibition constant (K(i)), and the inhibition mechanism were determined. A coumarin derivative with IC50 similar to tacrine was highlighted.

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This work reports the use of a two-dimensional liquid chromatography (2D-LC) system for quantification of the enantiomers of omeprazole in distinct native aqueous matrices. An octyl restricted-access media bovine serum albumin column (RAM-BSA C(8)) was used in the first dimension, while a polysaccharide-based chiral column was used in the second dimension with either ultraviolet (UV-vis) or ion-trap tandem mass spectrometry (IT-MS/MS) detection. An in-line configuration was employed to assess the exclusion capacity of the RAM-BSA columns to humic substances. The excluded macromolecules had a molecular mass in the order of 18 kDa. Good selectivity, extraction efficiency, accuracy, and precision were achieved employing a very small amount (500 microL or 1.00 mL) of native water sample per injection, with detection limits of 5.00 microg L(-1), using UV-vis, and 0.0250 microg L(-1), using IT-MS/MS. The total analysis time was only 35 min, with no time spent on sample preparation. The methods were successfully applied to analyze a series of waste and estuarine water samples. The enantiomers were detected in an estuarine water sample collected from the Douro River estuary (Portugal) and in an influent sample from the wastewater treatment plant (WWTP) of São Carlos (Brazil). As far as we are concerned, this is the first report of the occurrence of (+)-omeprazole and (-)-omeprazole in native aqueous matrices.

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The resolution of the natural racemic chromane 3,4-dihydro-5-hydroxy-2,7-dimethyl-8-(3''-methyl-2''-butenyl)-2-(4'-methyl-1',3'-pentadienyl)-2H-1-benzopyran-6-carboxylic acid (1) isolated from the leaves of Peperomia obtusifolia has been accomplished using stereoselective HPLC. The absolute configuration of the resolved enantiomers was determined by the analysis of optical rotations and CD spectra. The finding of a racemic mixture instead of an enantiomerically pure metabolite raises questions about the final steps in the biosynthesis of this class of natural products, suggesting that the intramolecular chromane ring formation step may not be enzymatically controlled at all in P. obtusifolia.