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

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 www.mdpi.com 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 submissions that pass pre-check are 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 2700 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.)