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197 results on '"Gikas, Evagelos"'

15. METABOLOMIC SIGNATURE OF AORTIC VALVE STENOSIS IN THE RABBIT MODEL

Author

Anousakis-Vlachochristou, Nikolaos, primary, Barla, Ioanna, additional, Gikas, Evagelos, additional, Mavroidis, Manolis, additional, Katsa, Maria, additional, Panara, Anthi, additional, THOMAIDIS, NIKOLAOS, additional, Cokkinos, Dennis V., additional, and Toutouzas, Konstantinos P., additional

Published
2023
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22. Colistimethate Acidic Hydrolysis Revisited: Arrhenius Equation Modeling Using UPLC-QToF MS

Author

Dagla, Ioanna Tsarbopoulos, Anthony Gikas, Evagelos

Subjects
health care economics and organizations
Abstract

Colistimethate (CMS), the prodrug of polymyxin E (colistin), is an antibiotic widely used as a last-line therapy against multidrug resistant Gram-negative bacteria, but little is known about its pharmacokinetics as its administration has stopped as a result of high neuro- and nephro-toxicity. The measurement of CMS levels in patients' biological fluids is of great importance in order to find the optimal dose regimen reducing the drug toxicity. Until now, CMS assay methods are based on the indirect determination after its hydrolysis to colistin (CS). Herein, the aim is to find the optimal conditions for the complete hydrolysis of CMS to CS. The reaction was studied at accelerated conditions: 40 degrees C, 50 degrees C, and 60 degrees C, and the results were evaluated by assessing the Arrhenius equation and computation employing the Tenua software. A validated analytical methodology based on ultra-performance liquid chromatography (UPLC) coupled to a hybrid quadrupole time of flight (QToF) instrument is developed for the simultaneous measurement of CMS and CS. The current methodology resulted in complete hydrolysis, in contrast with the previously reported one.

Published
2021

23. Targeted Metabolomics: The LC-MS/MS Based Quantification of the Metabolites Involved in the Methylation Biochemical Pathways

Author

Ntasi, Georgia Tsarbopoulos, Anthony Mikros, Emmanuel Gikas, Evagelos

Abstract

Biochemical methylation reactions mediate the transfer of the methyl group regulating vital biochemical reactions implicated in various diseases as well as the methylation of DNA regulating the replication processes occurring in living organisms. As a finite number of methyl carriers are involved in the methyl transfer, their quantification could aid towards the assessment of an organism’s methylation potential. An Hydrophilic Interaction Chromatography-Liquid Chromatography Multiple Reaction Monitoring (HILIC-LC-MRM) mass spectrometry (MS) methodology was developed and validated according to Food & Drug Administration (FDA), European Medicines Agency (EMA), and International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) for the simultaneous determination of nine metabolites i.e., B12, folic acid, 5-methyltetrahydrofolate, S-adenosylmethionine, S-adenosylhomocysteine, betaine, phosphocholine, N,N-dimethylglycine, and deoxythymidine monophosphate in human blood plasma. The sample pretreatment was based on a single step Solid-phase extraction (SPE) methodology using C18 cartridges. The methodology was found to accurately quantitate the analytes under investigation according to the corresponding dynamic range proposed in the literature for each analyte. The applicability of the method was assessed using blood donor samples and its applicability demonstrated by the assessment of their basal levels, which were shown to agree with the established basal levels. The methodology can be used for diagnostic purposes as well as for epigenetic screening.

Published
2021

29. Human Melanoma-Cell Metabolic Profiling: Identification of Novel Biomarkers Indicating Metastasis

Author

Kosmopoulou, Mariangela, primary, Giannopoulou, Aikaterini F., additional, Iliou, Aikaterini, additional, Benaki, Dimitra, additional, Panagiotakis, Aristeidis, additional, Velentzas, Athanassios D., additional, Konstantakou, Eumorphia G., additional, Papassideri, Issidora S., additional, Mikros, Emmanuel, additional, Stravopodis, Dimitrios J., additional, and Gikas, Evagelos, additional

Published
2020
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30. Malignancy Grade-Dependent Mapping of Metabolic Landscapes in Human Urothelial Bladder Cancer: Identification of Novel, Diagnostic, and Druggable Biomarkers

Author

Iliou, Aikaterini, primary, Panagiotakis, Aristeidis, additional, Giannopoulou, Aikaterini F., additional, Benaki, Dimitra, additional, Kosmopoulou, Mariangela, additional, Velentzas, Athanassios D., additional, Tsitsilonis, Ourania E., additional, Papassideri, Issidora S., additional, Voutsinas, Gerassimos E., additional, Konstantakou, Eumorphia G., additional, Gikas, Evagelos, additional, Mikros, Emmanuel, additional, and Stravopodis, Dimitrios J., additional

Published
2020
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31. Development and Validation of a UPLC–ESI(-)–MS/MS Methodology for the Simultaneous Quantification of Hesperidin, Naringin, and their Aglycones in Chicken Tissue Samples

Author

Baira, Eirini, primary, Dagla, Ioanna, additional, Siapi, Eleni, additional, Zoumpoulakis, Panagiotis, additional, Tsarbopoulos, Anthony, additional, Simitzis, Panagiotis, additional, Goliomytis, Michael, additional, Deligeorgis, Stelios G, additional, Skaltsounis, Alexios-Leandros, additional, and Gikas, Evagelos, additional

Published
2020
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38. Integrated HPTLC-based Methodology for the Tracing of Bioactive Compounds in Herbal Extracts Employing Multivariate Chemometrics. A Case Study on Morus alba.

Author

Chaita, Eliza, Gikas, Evagelos, and Aligiannis, Nektarios

Abstract

Introduction In drug discovery, bioassay-guided isolation is a well-established procedure, and still the basic approach for the discovery of natural products with desired biological properties. However, in these procedures, the most laborious and time-consuming step is the isolation of the bioactive constituents. A prior identification of the compounds that contribute to the demonstrated activity of the fractions would enable the selection of proper chromatographic techniques and lead to targeted isolation. Objective The development of an integrated HPTLC-based methodology for the rapid tracing of the bioactive compounds during bioassay-guided processes, using multivariate statistics. Materials and Methods - The methanol extract of Morus alba was fractionated employing CPC. Subsequently, fractions were assayed for tyrosinase inhibition and analyzed with HPTLC. PLS-R algorithm was performed in order to correlate the analytical data with the biological response of the fractions and identify the compounds with the highest contribution. Two methodologies were developed for the generation of the dataset; one based on manual peak picking and the second based on chromatogram binning. Results and Discussion - Both methodologies afforded comparable results and were able to trace the bioactive constituents (e.g. oxyresveratrol, trans-dihydromorin, 2,4,3′-trihydroxydihydrostilbene). The suggested compounds were compared in terms of Rf values and UV spectra with compounds isolated from M. alba using typical bioassay-guided process. Conclusion Chemometric tools supported the development of a novel HPTLC-based methodology for the tracing of tyrosinase inhibitors in M. alba extract. All steps of the experimental procedure implemented techniques that afford essential key elements for application in high-throughput screening procedures for drug discovery purposes. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2017
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39. New Facile Synthesis of 7-Hydroxy-6-amino-4-substituted Benzopyran-2-ones

Author

Vavagianis Andreas, Kazanis Michael, Gikas Evagelos, and Parissi‐Poulou Maria

Subjects
chemistry.chemical_compound, Group (periodic table), Hydrogen bond, Chemistry, Intramolecular force, Organic Chemistry, Benzopyran-2-ones, Organic chemistry, Reactivity (chemistry), General Medicine, Pechmann condensation, Selectivity, Coumarin
Abstract

A new facile synthesis of 6‐amino‐7‐hydroxy‐4‐substituted benzopyranones is described through the von Pechmann reaction. The yields obtained were high, and the proposed methodology leads to pure products. The selectivity of formation of the desired products can be attributed to the formation of an intramolecular hydrogen bond, which leads to reduced reactivity of the 2‐hydroxyl group.

Published
2005

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