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Special Issue "Activity of the Kynurenine Pathway: Analysis of Tryptophan and its Metabolites in Biological Samples by Chromatographic Techniques Coupled with Modern Detection Techniques"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Analytical Chemistry".

Deadline for manuscript submissions: closed (30 June 2020).

Special Issue Editor

Prof. Dr. Tomasz Tuzimski
E-Mail Website
Guest Editor
Department of Physical Chemistry, Medical University of Lublin, Chodźki 4a, 20-093 Lublin, Poland
Interests: theory and application of liquid chromatography; modern extraction techniques (eg., QuEChERS); detection techniques (DAD, FLD, MS, MS/MS); method development and validation; optimisation of chromatographic systems for separation and quantitative analysis of xenobiotics and others (multicomponent mixtures) in food, environmental and biological samples
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Special Issue Information

Dear Colleagues,

Tryptophan is one of the 10 essential amino acids that is predominantly metabolized by mammalian brain and peripheral tissues and plays an important role in protein synthesis and as a precursor of many biologically active substances. Tryptophan metabolism via the kynurenine pathway is essential in several fundamental biological processes, including neuronal excitability, antioxidant status, cell growth, and cell division in various cell types. The kynurenine pathway also mediates interactions between immunological and neuronal functions, and this interrelationship has been implicated in the pathophysiology of a wide range of disorders, such as human immune deficiency virus (HIV) infection, Huntington’s disease, malaria, major depression, and schizophrenia.

The challenge for the analyst is to develop effective and validated analytical strategies for the analysis of different activity compounds of the kynurenine pathway in biological sample types, quickly, accurately, and at an acceptable cost. It is highly beneficial to monitor the activity of the kynurenine pathway in a large series of samples with high accuracy and reliability in a single experimental protocol. The most efficient approach to tryptophan and its metabolites analysis involves the use of chromatographic methods. The following chromatographic methods are most frequently applied in biological samples analysis: High-performance liquid chromatography (HPLC), ultrahigh-performance liquid chromatography (UPLC), and others.

The Special Issue is planned as a forum that will present, in a properly structured manner, the up-to-date, state-of-the-art information on the very important field of high-performance chromatographic techniques coupled with modern detection techniques, e.g., mass spectrometry. It is a well-established fact that chromatographic techniques with mass spectrometry (MS) and tandem mass spectrometry (MS/MS) or with other modern detection techniques find a broad application in separation, identification, and quantification of the important components, such as tryptophan and its metabolites (kynurenine, kynurenic acid (KYNA), 3-hydroxyanthranilic acid (3OHAA), 3-hydroxykynurenine, anthranilic acid, quinolinic acid (QA), picolinic acid, xanthurenic acid, and others).

I warmly invite our colleagues to submit their original contributions to this Special Issue in order to provide recent updates regarding chromatographic methods for tryptophan analysis and activity analytes of the kynurenine pathway related to biological samples, which will be of interest to our readers.

I would be delighted if you could respond to confirm your contribution and the proposed title by 30 June 2019 to assist in planning the whole project. In cases of review articles, an additional brief (1–2-page) description of the topic including a draft index is required. This preliminary step is essential to avoid overlapping of topics. The degree of novelty and the significance of the research will be scrutinized prior to the peer-reviewing process.

Dr. Tomasz Tuzimski (Ph.D., Adjunct Professor)
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


  • tryptophan and its metabolites (kynurenine, kynurenic acid (KYNA), 3-hydroxyanthranilic acid, 3-hydroxykynurenine, anthranilic acid, quinolinic acid, picolinic acid, etc.)
  • extraction techniques (SPE, QuEChERS/d-SPE, etc.)
  • chromatographic methods (HPLC, UPLC, etc.)
  • detection techniques (MS, MS/MS, FLD, DAD, etc.)

Published Papers (1 paper)

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Structural Evaluation and Electrophysiological Effects of Some Kynurenic Acid Analogs
Molecules 2019, 24(19), 3502; - 26 Sep 2019
Cited by 7 | Viewed by 1108
Kynurenic acid (KYNA), a metabolite of tryptophan, as an excitatory amino acid receptor antagonist is an effective neuroprotective agent in case of excitotoxicity, which is the hallmark of brain ischemia and several neurodegenerative processes. Therefore, kynurenine pathway, KYNA itself, and its derivatives came [...] Read more.
Kynurenic acid (KYNA), a metabolite of tryptophan, as an excitatory amino acid receptor antagonist is an effective neuroprotective agent in case of excitotoxicity, which is the hallmark of brain ischemia and several neurodegenerative processes. Therefore, kynurenine pathway, KYNA itself, and its derivatives came into the focus of research. During the past fifteen years, our research group has developed several neuroactive KYNA derivatives, some of which proved to be neuroprotective in preclinical studies. In this study, the synthesis of these KYNA derivatives and their evaluation with divergent molecular characteristics are presented together with their most typical effects on the monosynaptic transmission in CA1 region of the hippocampus of the rat. Their effects on the basic neuronal activity (on the field excitatory postsynaptic potentials: fEPSP) were studied in in vitro hippocampal slices in 1 and 200 μM concentrations. KYNA and its derivative 4 in both 1 and 200 μM concentrations proved to be inhibitory, while derivative 8 only in 200 μM decreased the amplitudes of fEPSPs. Derivative 5 facilitated the fEPSPs in 200 μM concentration. This is the first comparative study which evaluates the structural and functional differences of formerly and newly developed KYNA analogs. Considerations on possible relations between molecular structures and their physiological effects are presented. Full article
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