oa Editorial [Hot Topic: Analytical Aspects in Drug Metabolism (Guest Editor: Constantinos K. Zacharis)]

Drug metabolism studies offer significant information on the clarification of the pharmacological and toxicological action of drugs and typically include isolation and identification of metabolites generated in vivo and in vitro. On the other hand, analytical chemistry and chemical analysis are useful tools that are ad nausea used in drug metabolism studies since they provide invaluable information. Among others, separation techniques (liquid chromatography, mass spectrometry, etc) are predominant when it comes to the analysis of complex matrices where enhanced selectivity and sensitivity is required. For instance, mass spectrometry could be considered to be the technique of choice that used in the elucidation of metabolic pathways of drugs. The aim of the current Hot Topic Issue of the international journal Current Drug Metabolism intends to provide to the scientific community comprehensive reviews covering the new trends and applications in the area of Analytical Chemistry towards Drug Metabolism and Biological Systems. The introductory paper by the research group of Prof. D.S. Hage aims towards to the characterization of drug interactions with serum proteins by high performance affinity chromatography. It covers theoretical and practical aspects on the studies of drug-protein interactions by affinity chromatography illustrating recent applications of the use of serum binding agents like human serum albumin, α1-acid glycoprotein and lipoproteins. Prof. Longsheng Sheng and his colleagues focused on a review dedicated to recent developments of LC-MS in drug metabolite identification. They describe a variety of experimental strategies and post acquisition data processing modes; tools that are needed of identification and characterization of drug metabolites. Finally, the authors comprehensively discussed aspects on mass spectrometric techniques including low resolution (quadrupole, ion trap, etc), high resolution MS analyzers (time-of-flight, Orbitrap, Fourier transform ion cyclotron resonance MS, etc) and novel MS technologies (ion mobility MS, imaging MS, etc). During the last years the -omics sciences (proteomics, genomics, metabolomics) are growing rapidly and on this basis the contribution of Dr. R. Wei, offers a complete overview of metabolomics and its practical value in pharmaceutical industries. Except for the brief historical overview of metabolomics, this article illustrates its practical role in pharmaceutical industries' issues dealing with validation of novel therapeutic targets, decision-making in the drug development processes and clinical trials. A selection of examples in metabolomics studies were also reviewed focusing on biochemical changes associates with pharmaceutical interventions. The research group of Dr. H.P. Permentier focused on the utilization of electrochemistry as a versatile analytical and preparative technique in the mimicry of oxidative drug metabolism by Cytochrome450s. This review also highlights oxidation methodologies that imitate the in vivo oxidation reactions including direct oxidation approaches and indirect electrochemical oxidation reactions by reactive oxygen species. Dr. J.M.P.J. Garrido briefly discussed the electrochemical outlook of tamoxifen biotransformation. This article includes the most important biotransformation steps of tamoxifen (a non-steroidal antiestrogen) based on recent pharmacological data and some applications of electrochemical methods for the determination of the drug and its metabolites. Prof. H. Orhan provides an important review on approaches in generating and characterization of reactive intermediates from drugs and drug candidates. They draw our attention to main criteria which a drug candidate should meet during its development and on reactive intermediates generated by biotransformation of the parent drug. Basic aspects on the screening and characterization of reactive intermediates using mass spectrometric techniques are also discussed. Finally, the research group of Prof. A. van Schepdael contributed an article orientated towards matrix metalloproteinase inhibitors. They focused on bioanalytical methodologies for the determination of matrix metalloproteinase inhibitors and their metabolites underlining aspects on sample preparation and detection techniques. In particular they describe features on pharmacokinetics and metabolism of matrix metalloproteinase inhibitors and their metabolites. From the position of the Guest Editor of this special issue, I would like to thank the Editor-in-Chief of Current Drug Metabolism Dr. Chandra Prakash for accepting my proposal to organize this special issue. Finally, I would like to thank all colleagues from all over the world that accepted my invitation and contributed with their high quality articles to this effort.