LC-ESI/LTQ-Orbitrap-MS Based Metabolomics in Evaluation of Bitter Taste of Arbutus unedo Honey

Strawberry tree honey is a high-value honey from the Mediterranean area and it is characterised by a typical bitter taste. To possibly identify the secondary metabolites responsible for the bitter taste, the honey was fractionated on a C18 column and the individual fractions were subjected to sensory analysis and then analysed by liquid chromatography coupled with high-resolution tandem mass spectrometry in negative ion mode, using a mass spectrometer with an electrospray source coupled to a hybrid high resolution mass analyser (LC-ESI/LTQ-Orbitrap-MS). A chemometric model obtained by preliminary principal component analysis (PCA) of LC-ESI/LTQ-Orbitrap-MS data allowed the identification of the fractions that caused the perception of bitterness. Subsequently, a partial least squares (PLS) regression model was built. The studies carried out with multivariate analysis showed that unedone (2-(1,2-dihydroxypropyl)-4,4,8-trimethyl-1-oxaspiro [2.5] oct-7-en-6-one) can be considered responsible for the bitter taste of strawberry tree honey. Confirmation of the bitter taste of unedone was obtained by sensory evaluation of a pure standard, allowing it to be added to the list of natural compounds responsible for giving the sensation of bitterness to humans.

Gas phase protonated nicotine is a mixture of pyridine- and pyrrolidine-protonated conformers: implications for its native structure in the nicotinic acetyl-choline receptor

The infrared (IR) spectra of gas phase protonated nicotine has been measured in the never-before probed N-H “fingerprint region” (3,200–3,500 cm−1). The protonated molecules generated by an electrospray source are...

Validation of a quick and simple chromatographic method for simultaneous quantification of sertraline, escitalopram, risperidone and paliperidone levels in the human plasma

Simultaneous quantification of multiple psychiatric drugs is important for the therapeutic drug monitoring of psychiatric patients. In addition, it would be highly advantageous if the method could be simple, straightforward, and not time-consuming. A 200 µl plasma sample was deproteinized, drugs were separated by a ZORBAX Eclipse XDB-Phenyl column with the mobile phase composed of acetonitrile and 0.1 % formic acid in water (60:40, v/v), and recorded in the MRM mode by using a positive electrospray source with tandem mass spectrometry detection. The dynamic range was 2-256 ng/ml for all the analyzed drugs, except escitalopram (8-256 ng/ml). Quality control samples were prepared in quintuplicates in three relevant concentrations for each drug. Coefficients of determination (R2 ) were higher than 0.99, while the relative difference between nominal and measured concentrations (RE) and CV were lower than 15% for all targets. High performance liquid chromatography coupled with the mass detector (HPLC-MS/MS) method for simultaneous determination of sertraline, escitalopram, risperidone and paliperidone in human plasma was validated with respect to selectivity, linearity, accuracy, precision, matrix effect and stability. This method has significant advantages in terms of low sample volume (200 µl), short preparation time (3 hours) and short runtime per sample (4 minutes).

Modern methods for regulation nicotine containing products

Issues of assessing the content of carbonyl compounds in the aerosol of innovative nicotine-containing products: nicotine delivery systems of various designs (LUXLITE, VON ERL My, iKuu i200) and electric tobacco heating system iQOS, by high-performance liquid chromatography/mass spectrometry. At the international level (CORESTA, ISO/TC 126), a lot of work is being done to create methods for quality control of nicotine-containing products. Requirements for nicotine-containing products are not regulated within the EAEU. The monitoring of world studies to determine the content of toxic and conditionally toxic components of aerosol NSP, carried out using the method of machine Smoking. Vniitti IS developing a methodology for comprehensive evaluation of innovative nicotine-containing products on the basis of modern methods of product quality control. Of particular interest is the determination of the content of carbonyl compounds in the aerosol generated by SDN and ESNT, which started in the laboratory of tobacco production technology within the Eurasian Economic Union. The results of machine Smoking according to the canadian intensive method, ISO method, VNIITTI method, standard and experimental CORESTA methods are analyzed. Developed testing methodology and collection of aerosol-nicotine produce using a laboratory five-CERULEAN Smoking machines SM 405. The technique of quantitative determination of carbonyl compounds using high-performance liquid chromatomass spectrometry LCMS/MS by detection at an electrospray source in the negative polarity mode on analytical equipment was validated: chromatograph Thermo Scientific Dionex UltiMate 3000 and mass spectrometer TSQ Quantiva. Validation of methods for collecting and determining the content of carbonyl compounds (formaldehyde, acetaldehyde and acrolein) in the aerosol of nicotine-containing products of various types allowed to obtain reliable data to establish the potential of innovative products to reduce the risk compared with traditional cigarettes. Experimental data on the quantitative determination of carbonyl compounds in the NSP aerosol were obtained. Further research will focus on the development of evidence-based safety requirements for innovative types of nicotine-containing products.

Масс-спектрометрическое наблюдение иона С-=SUP=-+-=/SUP=- при электрораспылении с атомизацией в источнике

Carbon C^+ ions formed in a mass-spectrometric electrospray source with controlled in-source fragmentation and atomization interface have been observed for the first time. The measurements were performed in a special MI-20 LowMass mass spectrometer (MS-Bio LLC) using aqueous methanol solutions of lithium and beryllium salts. The peak of C^+ ions was substantially broadened as compared to the peaks of metal ions. A model is proposed that explains the formation of C^+ ions due to charge exchange immediately at the high-vacuum boundary near the skimmer output.

Non-scrambling of hydrogen in NH4+(H2O)3 clusters

We have measured the metastable decay of protonated, ammonia-doped, deuterated water clusters produced in an electrospray source, dn-NH4+(H2O)3, n = 0–6.

Novel contribution to the simultaneous monitoring of pramipexole dihydrochloride monohydrate and levodopa as co-administered drugs in human plasma utilizing UPLC–MS/MS

An efficient, selective, sensitive, and rapid ultra-performance liquid chromatography tandem mass spectrometry method was established and validated for the quantification of pramipexole dihydrochloride monohydrate and levodopa simultaneously in human plasma with the aid of diphenhydramine as an internal standard. A simple protein precipitation technique with HPLC grade acetonitrile was efficiently utilized for the cleanup of plasma. The analysis was performed using a Hypersil gold 50 mm × 2.1 mm (1.9 µm) column and a mobile phase of 0.2% formic acid and methanol (90: 10 v/v). The triple-quadrupole mass spectrometer equipped with an electrospray source operated in the positive mode was set up in the selective reaction monitoring mode (SRM) to detect the ion transitions m/z 212.15 →153.01, m/z 198.10→ 135.16, and m/z 255.75 → 166.16 for pramipexole dihydrochloride monohydrate, levodopa, and diphenhydramine, respectively. The method was thoroughly validated according to FDA guidelines and proved to be linear, accurate, and precise over the range 100–4000 pg/mL for pramipexole dihydrochloride monohydrate and 60–4000 ng/mL for levodopa. The proposed method was effectively applied for monitoring both drugs in plasma samples of healthy volunteers.

Thermal Denaturation of DNA G-Quadruplexes and their Complexes with Ligands: Thermodynamic Analysis of the Multiple States Revealed by Mass Spectrometry

ABSTRACTAs the idea that G-quadruplex nucleic acid structures are involved in cellular processes is gaining support, it becomes important to develop ligands that specifically target G-quadruplexes. However, ligand design is complicated because there are multiple G-quadruplex target sequences, some sequences are polymorphic, and very few ligand-quadruplex structures in solution were solved to date. Further, structure alone does not reveal the driving forces for ligand binding. To know why a ligand binds, the thermodynamics of binding must be characterized. Electrospray mass spectrometry makes it possible to detect and quantify each specific stoichiometry in terms of number of strands, number of specific cations, and number of ligands, and thus allows one to simultaneously determine the equilibrium constants for the formation of each complex. We designed and built a temperature-controlled nano-electrospray source to monitor thermal denaturation by mass spectrometry (“MS-melting”). We studied the thermal denaturation of G-quadruplexes, including the c-myc promoter and several telomeric sequence variants, and their complexes with popular ligands (Phen-DC3, TrisQ, TMPyP4, Cu-ttpy). From the temperature dependence of the equilibrium constants, we determined the enthalpic and entropic contributions to the formation of each stoichiometric state. In absence of ligand, we untangled the potassium-induced G-quadruplex folding thermodynamics, one potassium ion at a time. The formation of each quartet-K+-quartet units is strongly enthalpy driven, with entropy penalty. In contrast, the formation of quartet-K+-triplet units is entropically driven. For this reason, such misfolded structures can become more abundant as the temperature increases. In the presence of ligands, mass spectrometry also revealed new states at intermediate temperatures. For example, even in cases where only a 1:1 (ligand:quadruplex) is observed at room temperature, a 2:1 complex predominates at intermediate temperatures. Mass spectrometry also makes it easy to distinguish ligand bound to the 2-quartet structures (containing 1 K+), the 3-quartet structures (containing 2 K+) and to the unfolded strand (no specific K+). We confirm that TrisQ binds preferably, but not exclusively, to 3-quartet structures, Phen-DC3 binds to a 2-quartet structure, while the porphyrin ligand TMPyP4 is characterized as non-selective, because it binds to all forms including the unfolded one. The thermodynamics of ligand binding to each form, one ligand at a time, provides unprecedented detail on the interplay between ligand binding and changes in G-quadruplex topology.TOC Graphics