Determination of the adenosine A(1) agonist N(6)-cyclopentyladenosine in rat blood by solid-phase extraction and HPLC

Poly(glycidyl methacrylate-co-N-methylolacrylamide-co-ethylene dimethacrylate) monolith coupled to high-performance liquid chromatography for the determination of adenosine phosphates in royal jelly

A polymer monolith microextraction method coupled with high-performance liquid chromatography was developed for the determination of adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate. The monolithic column was synthesized inside fused-silica capillaries using thermal initiation free-radical polymerization with glycidyl methacrylate as the monomer, ethylene dimethacrylate as the cross-linker, cyclohexanol, and 1-dodecanol as the porogen. N-Methylolacrylamide, an important hydrophilic monomer, was incorporated into the polymerization mixture to enhance the hydrophilicity of the poly(glycidyl methacrylate-co-ethylene dimethacrylate) column. The obtained poly(glycidyl methacrylate-co-N-methylolacrylamide-co-ethylene dimethacrylate) monolith was characterized by scanning electron microscopy, Fourier-transform infrared spectra, and X-ray photoelectron spectroscopy. Optimum conditions for the preconcentration and separation of the target adenosines were also investigated. Under the optimum conditions, we obtained acceptable linearities, low limits of detection, and good relative standard deviations. The developed polymer monolith microextraction with high-performance liquid chromatography method exhibited a good performance with recovery values in the range of 76.9-104.7% when applied to the determination of the adenosines in five royal jelly samples.

Quantitative analysis of adenosine using liquid chromatography/atmospheric pressure chemical ionization-tandem mass spectrometry (LC/APCI-MS/MS)

Adenosine-secreting cellular brain implants constitute a promising therapeutic approach for the treatment of epilepsy. To engineer neural stem cells for therapeutic adenosine delivery, a reliable and fast analytical method is necessary to quantify cell-based adenosine release. Here we describe the development, optimization and validation of adenosine measurement using liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (LC-APCI-MS/MS). LC-MS/MS in positive ion mode used selected reaction monitoring at m/z of 268.2/136.1 and 302.2/170.0 for adenosine and the internal standard, respectively. The bias was within 15% of the nominal value and evaluation of precision showed a relative standard deviation lower than 15% for all measured concentrations. The lower limit of quantification of adenosine was 15.6 ng/ml. Freeze and thaw stability and processed sample stability also fulfilled the acceptance criteria. Evaluation of the matrix effect showed that the method is not affected by relative matrix effects. The major advantages of this method are the absence of an extraction phase and the combination of the high selectivity and sensitivity characteristic for the LC-MS/MS technique, with a short run time of 4.5 min. These results demonstrate that this method is a useful tool to measure adenosine concentrations in culture medium released from stem cells in vitro.

Development of a Method for Quantification of Acrolein−Deoxyguanosine Adducts in DNA Using Isotope Dilution-Capillary LC/MS/MS and Its Application to Human Brain Tissue

Acrolein is a highly reactive alpha,beta-unsaturated aldehyde and is known to react with DNA forming exocyclic acrolein-deoxyguanosine adducts (Acro-dG). These aldehyde-DNA lesions may play a role in mutagenesis, carcinogenesis, and neurodegenerative diseases. In the present work, we described the development and evaluation of a highly sensitive and selective capillary liquid chromatography nanoelectrospray isotope dilution tandem mass spectrometry method for quantitatively analyzing Acro-dG in DNA hydrolysates. This was achieved by applying a stable isotope-labeled analogue Acro-dG-13C10,15N5 as an internal standard to the DNA to be analyzed and then hydrolyzing the DNA enzymatically to nucleosides. The acrolein-modified nucleosides were separated from normal nucleosides by capillary liquid chromatography and quantified by a high-capacity ion trap mass spectrometer in the MS/MS mode. The developed method achieved attomole-level sensitivity (limit of detection was 10 fg, 31 amol on column) for detection of pure Acro-dG adduct standards. The limit of quantification of Acro-dG adducts obtained in 10 mug of DNA hydrolysates was 1.5 fmol, which corresponded to 50 adducts/10(9) normal nucleosides. Application of this method to the analysis of Acro-dG adducts in acrolein (10-fold)-treated calf thymus DNA showed approximately 830 lesion/10(6) DNA nucleosides using as low as 50 ng of DNA. Application of this method to DNA samples (1-2 mug) isolated from brain tissues from Alzheimer's disease subjects and age-matched controls demonstrated 2800-5100 Acro-dG adducts/10(9) DNA nucleosides. Statistically significant differences (P < 0.05) in levels of Acro-dG between AD subjects and controls were observed in DNA isolated from the hippocampus/parahippocampal gyrus.

Simple and rapid determination of adenosine in human synovial fluid with high performance liquid chromatography-mass spectrometry

A simple, fast, sensitive and selective reversed-phase high performance liquid chromatography-mass spectrometry coupling with an electrospray ionization (ESI) interface method is described for the determination of adenosine in human synovial fluid. This method involved the use of the [M + H](+)ions of adenosine and 2-chloroadenosine (internal standard for the assay) at m/z 268 and 302 in positive ion mode with selective ion monitoring (SIM). Separation was carried out on a 2.0 x 150 mm Shimadzu VP-ODS column by using an isocratic elution with a mobile phase consisting of water (94%),methanol (5%) and formic acid (1%). No interference with the components of the biological matrix was observed in the determination conditions. The calibration curve was linear in the range of 0.2-140 microgml(-1). The limits of quantification (LOQ) and detection (LOD) were 0.2 and 0.03 microgml(-1), respectively. The standard recoveries were between 93.3 and 104.0%. The method was successfully applied to determination of adenosine in some synovial fluids of patients affected by rheumatoid arthritis.