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Pralidoxime salts are important medical countermeasures towards different organophosphorus compounds, either nerve agents or pesticides, as they act as acetylcholinesterase reactivators, avoiding health issues and even death that can result from intoxication with such chemicals. In this work, we present an expeditious study focuses on the optimization of a two‐step continuous‐flow synthesis of 2‐PAM. Initial attempts to replace the solvent composition in the oxime formation reaction with acetonitrile resulted in lower yields, highlighting the significance of a polar protic solvent. Subsequent optimization under continuous‐flow conditions revealed the successful execution of oxime formation at room temperature with a residence time of 20 minutes, achieving an impressive 96 % conversion, surpassing literature‐reported conditions. The methylation step required a high residence time of 60 minutes at 120 °C for a substantial conversion of 78 %. The two‐step continuous‐flow process demonstrated robustness, yielding 75 %, with space‐time yields of 0.32 g/h and 0.18 g/h. Further concentration adjustments increased space‐time yields to 3.2 g/h and 2.2 g/h. Despite solvent incompatibility, a strategic alteration of the reaction sequence allowed for a successful cascade process, integrating the methylation step in acetonitrile and the oxime formation in water. The continuous‐flow system, incorporating a heat exchanger, exhibited stability, maintaining full conversion and a space‐time yield of 0.3 g/h over extended periods. This systematic optimization not only enhances the efficiency of 2‐PAM synthesis but also provides insights into a scalable and practical continuous‐flow cascade process. [ABSTRACT FROM AUTHOR]

A selection of acidic, alkaline and neutral degradation products relevant to the Chemical Weapons Convention was studied in wide range of pH conditions to determine their spin systems as well as spectral parameters. The pH dependence of chemical shifts and J couplings was parameterized using Henderson–Hasselbalch‐based functions using dichloromethane as additional shift reference in TSP‐d4 referenced spectra. The resulting parameters allowed calculation of precise chemical shifts and J coupling constants in arbitrary pH conditions. The validity of the obtained spin system definitions and parameters as a source of quantum mechanically simulated reference data in chemical verification analysis is demonstrated. [ABSTRACT FROM AUTHOR]

The nerve agents of the A-series are relatively recent chemical weapons with no antidote available yet (1). Once inside the human body, those chemicals act similarly to the classic nerve agents, by binding to the catalytic residue Serine 203 (Ser203) of human acetylcholinesterase (HssAChE) and thus preventing the proper function of this enzyme. However, there is no experimental evidence yet if the current antidotes for intoxication by nerve agents are also capable of restoring AChE inhibited by the nerve agents of the A-series. In order to launch some light on this issue, we used computational techniques (molecular docking, molecular dynamics and MM-PBSA interaction energy calculations) to assess the performances of the four currently available commercial oximes (2-PAM, HI-6, obidoxime and trimedoxime) when in contact with HssAChE inhibited by the agent A-242 (2). Based on the nearattack conformation (NAC) criterion, our results suggest that the commercial oximes would have limited efficacy to reactivate the enzyme since they are not able to properly approach the adduct Ser203-A-242. Among those oximes, trimedoxime seems to be the most promising, since it showed lower values of energy in the MM-PBSA calculations, a higher stability inside the catalytic anionic center (CAS) of HssAChE and was able to adopt a position closer to the NAC that could enable the reactivation mechanism. [ABSTRACT FROM AUTHOR]

Organophosphorus compounds (OP) are chemicals widely used as pesticides in different applications such as agriculture and public health (vector control), and some of the highly toxic forms have been used as chemical weapons. After application of OPs in an environment, they persist for a period, suffering a degradation process where the biotic factors are considered the most relevant forms. However, to date, the biodegradation of OP compounds is not well understood. There are a plenty of structure-based biodegradation estimation methods, but none of them consider enzymatic interaction in predicting and better comprehending the differences in the fate of OPs in the environment. It is well known that enzymatic processes are the most relevant processes in biodegradation, and that hydrolysis is the main pathway in the natural elimination of OPs in soil samples. Due to this, we carried out theoretical studies in order to investigate the interactions of these OPs with a chosen enzyme—the phosphotriesterase. This one is characteristic of some soils' microorganisms, and has been identified as a key player in many biodegradation processes, thanks to its capability for fast hydrolyzing of different OPs. In parallel, we conducted an experiment using native soil in two conditions, sterilized and not sterilized, spiked with specific amounts of two OPs with similar structure—paraoxon-ethyl (PXN) and O-(4-nitrophenyl) O-ethyl methylphosphonate (NEMP). The amount of OP present in the samples and the appearance of characteristic hydrolysis products were periodically monitored for 40 days using analytical techniques. Moreover, the number of microorganisms present was obtained with plate cell count. Our theoretical results were similar to what was achieved in experimental analysis. Parameters calculated by enzymatic hydrolysis were better for PXN than for NEMP. In soil, PXN suffered a faster hydrolysis than NEMP, and the cell count for PXN was higher than for NEMP, highlighting the higher microbiological toxicity of the latter. All these results pointed out that theoretical study can offer a better comprehension of the possible mechanisms involved in real biodegradation processes, showing potential in exploring how biodegradation of OPs relates with enzymatic interactions. [ABSTRACT FROM AUTHOR]

Casualties caused by organophosphorus pesticides are a burden for health systems in developing and poor countries. Such compounds are potent acetylcholinesterase irreversible inhibitors, and share the toxic profile with nerve agents. Pyridinium oximes are the only clinically available antidotes against poisoning by these substances, but their poor penetration into the blood-brain barrier hampers the efficient enzyme reactivation at the central nervous system. In searching for structural factors that may be explored in future SAR studies, we evaluated neutral aryloximes as reactivators for paraoxon-inhibited Electrophorus eel acetylcholinesterase. Our findings may result into lead compounds, useful for development of more active compounds for emergencies and supportive care. [ABSTRACT FROM AUTHOR]

"Novichoks" is the name given to the controversial chemical weapons supposedly developed in the former Soviet Union between the 1970s and the 1990s. Designed to be undetectable and untreatable, these chemicals became the most toxic of the nerve agents, being very attractive for both terrorist and chemical warfare purposes. However, very little information is available in the literature, and the Russian government did not acknowledge their development. The intent of this review is to provide the IJMS readers with a general overview on what is known about novichoks today. We briefly tell the story of the secret development of these agents, and discuss their synthesis, toxicity, physical-chemical properties, and possible ways of treatment and neutralization. In addition, we also wish to call the attention of the scientific community to the great risks still represented by nerve agents worldwide, and the need to keep constant investments in the development of antidotes and ways to protect against such deadly compounds. [ABSTRACT FROM AUTHOR]

The present work aimed to compare the small, neutral and monoaromatic oxime, isatin-3-oxime (isatin-O), to the commercial ones, pralidoxime (2-PAM) and obidoxime, in a search for a new potential reactivator for acetylcholinesterase (AChE) inhibited by the pesticide paraoxon (AChE/POX) as well as a novel potential scaffold for further synthetic modifications. The multicriteria decision methods (MCDM) allowed the identification of the best docking poses of those molecules inside AChE/POX for further molecular dynamic (MD) studies, while Ellman's modified method enabled in vitro inhibition and reactivation assays. In corroboration with the theoretical studies, our experimental results showed that isatin-O have a reactivation potential capable of overcoming 2-PAM at the initial moments of the assay. Despite not achieving better results than obidoxime, this molecule is promising for being an active neutral oxime with capacity of crossing the blood–brain barrier (BBB), to reactivate AChE/POX inside the central and peripheral nervous systems. Moreover, the fact that isatin-O can also act as anticonvulsant makes this molecule a possible multipotent reactivator. Besides, the MCDM method showed to be an accurate method for the selection of the best docking poses generated in the docking studies. [ABSTRACT FROM AUTHOR]

Aflatoxins are secondary metabolites of the fungi Aspergillus flavus and A. parasiticus. Among them Aflatoxin B1 (AFB1) is the most frequent type in nature and the most carcinogenic and hepatotoxic for mammals. AFB1 is also inhibitor of the enzyme acetylcholinesterase (AChE) and, therefore, a potential chemical and biological warfare agent, as well as its metabolites. In order to investigate this, we performed inedited theoretical studies on the interactions of AFB1 and its metabolites inside the catalytic and the peripheral anionic sites (CAS and PAS) of human acetylcholinesterase (HssAChE), to verify their stability, suggest the preferential ways of inhibition, and compare their behavior to each other. Molecular docking, molecular dynamics and MM-PBSA calculations for the systems HssAChE/AFB1-metabolites, on both sites were performed. All the metabolites presented negative values of interaction energies in comparison to AFB1. This suggests that they can be better inhibitors of HssAChE. Also, the energy values obtained for the CAS were lower than for the PAS for all metabolites, suggesting that they may preferentially bind in the CAS and come closer to the active site. This behavior is different from the experimentally observed for AFB1, pointing to a different way of inhibition for its metabolites. [ABSTRACT FROM AUTHOR]

Nerve Agents are toxic organophosphorus compounds which inhibit cholinesterases, pivotal enzyme in Parasympathetic Neurotransmission. As they are Schedule 1 compounds in accordance to Chemical Weapons Convention, strict controls are applied and some research groups may have their work hampered due to requirements for synthesis and manipulation. Nerve Agents' surrogates have emerged as affordable substitutes for more realistic approach for development of antidotes and biochemical and toxicity studies, as they are structurally related to Nerve Agents and considered as CWC Schedule 2 compounds, yielding similar enzyme adducts. As Laboratório de Análises Químicas - LAQ (ISO 17025) at IDQBRN have been participated in OPCW Proficiency Tests, striven to obtain the "OPCW Designated Laboratory" status, we have synthesized different dialkyl alkylphosphonates for verification purposes. Therefore, we have proposed synthesis of surrogates for our research on Medicinal Chemistry using them as starting materials. They have proven to be very useful compounds in our research and our syntheses have delivered good yields and purity of final compounds. [ABSTRACT FROM AUTHOR]

The nerve agents of the A-series are relatively recent chemical weapons with no antidote available yet. Once inside the human body, those chemicals act similarly to the classic nerve agents, by binding to the catalytic residue Serine 203 (Ser203) of human acetylcholinesterase (HssAChE) and thus preventing the proper function of this enzyme. However, there is no experimental evidence yet if the current antidotes for intoxication by nerve agents are also capable of restoring AChE inhibited by the nerve agents of the A-series. In order to launch some light on this issue, we used computational techniques (molecular docking, molecular dynamics and MM-PBSA interaction energy calculations) to assess the performances of the four currently available commercial oximes (2-PAM, HI-6, obidoxime and trimedoxime) when in contact with HssAChE inhibited by the agent A-242. Based on the near-attack conformation (NAC) criterion, our results suggest that the commercial oximes would have limited efficacy to reactivate the enzyme since they are not able to properly approach the adduct Ser203-A-242. Among those oximes, trimedoxime seems to be the most promising, since it showed lower values of energy in the MM-PBSA calculations, a higher stability inside the catalytic anionic center (CAS) of HssAChE, and was able to adopt a position closer to the NAC that could enable the reactivation mechanism., (Copyright © 2022 Elsevier Ltd. All rights reserved.)