Advances in the Development of Reactivators for the Treatment of Organophosphorus Inhibited Cholinesterase

Synthesis and evaluation of small organic molecule as reactivator of organophosphorus inhibited acetylcholinesterase

A series of uncharged salicylaldehyde oximes were synthesized and evaluated for the reactivation of organophosphorus (OP) nerve agents simulants Diethylchlorophosphonate (DCP) & Diethylcyanophosphonate (DCNP) and pesticides (paraoxon & malaoxon) inhibited electric eel Acetylcholinesterase (AChE). The computational software Swiss ADME and molinspiration were used to unfold the probability of drug-likeness properties of the oximes derivatives. Substituted aromatic oximes with diethylamino or bromo group with free hydroxyl group ortho to oxime moiety were found efficient to regenerate the enzymatic activity in in-vitro AChE assay. The alkylation of the ortho hydroxyl group of derivatives led to the loss of reactivation potential. The derivatives with a hydroxyl group and without oxime group and vice versa did not show significant reactivation potency against tested OP toxicants. Further, we also evaluated the reactivation potential of these selected molecules on the rat brain homogenate against different OPs inhibited ChE and found maximum reactivation potency of oxime 2e. The in-vitro results were further validated by molecular docking and dynamic studies which showed that the hydroxyl group interacted with serine amino acids in the catalytic anionic site of AChE enzyme and was stable up to 200 ns consequently providing proper orientation to oxime moiety for reactivating the OP inhibited enzyme. It has thus been proved by the structure-activity relationship of oximes derivatives that hydroxyl group ortho to oxime is essential for reactivating OP inhibited electric eel AChE. Amongst the twenty-one oximes derivatives, 2e was found to be most active in regenerating the paraoxon, malaoxon, DCP and DCNP inhibited AChE enzyme.

Simple and efficient PET and AIEE mechanism-based fluorescent probes for sensing Tabun mimic DCNP

The highly sensitive, selective, easy-to-prepare, aqueous media based on two novel probes 2-(pyren-1-yl)imidazo[1,2-a]pyridine (IMP-Py) and (2-(pyren-1-yl)imidazo[1,2-a]pyridin-3-yl)methanol (IMP-Py-OH) are synthesized for the detection of toxic chemical warfare nerve agent mimic diethylcyanochlorophosphonate (DCNP). Both probes are found effective in the detection of DCNP but comparatively, IMP-Py shows better properties in terms of instantaneous response, specificity, selectivity and a low detection limit of 16.9 nM. A significant enhancement of fluorescence intensity of IMP-Py due to aggregation-induced emission enhancement (AIEE) and photoinduced electron transfer (PET) phenomenon was inhibited due to phosphorylation of the hydroxy group of IMP-Py-OH in presence of DCNP has been observed. Taking the advantages of good sensitivity and fast response, probe IMP-Py has been fabricated into a viable paper strips portable product, tested for its potential for the detection of DCNP in tap water as well as with its vapor and response is visible under a UV lamp of 365 nm wavelength.

Progress in the Development of Imidazopyridine-Based Fluorescent Probes for Diverse Applications

Different classes of Imidazopyridine i.e., Imidazo[1,2-a]pyridine, Imidazo[1,5-a] pyridine, Imidazo[4,5-b]pyridine, have shown versatile applications in various fields. In this review, we have concisely presented the usefulness of the fluorescent property of imidazopyridine in different fields such as imaging tools, optoelectronics, metal ion detection, etc. Fluorescence mechanisms such as excited state intramolecular proton transfer, photoinduced electron transfer, fluorescence resonance energy transfer, intramolecular charge transfer, etc. are incorporated in the designed fluorophore to make it for fluorescent applications. It has been widely employed for metal ion detection, where selective metal ion detection is possible with triazole-attached imidazopyridine, β-carboline imidazopyridine hybrid, quinoline conjugated imidazopyridine, and many more. Also, other popular applications involve organic light emitting diodes and cell imaging. This review shed a light on recent development in this area especially focusing on the optical properties of the molecules with their usage which would be helpful in designing application-based new imidazopyridine derivatives.

Imidazo[1,2-a]pyridine based small organic fluorescent molecules for selective detection of nerve agents simulants

A fused heterocyclic ESIPT imidazo[1,2-a]pyridine-based probes for colorimetric and fluorometric detection of nerve agents simulant sarin (DCP) and tabun (DCNP) are reported. The probes (5b, 6a & 6b) were found to be highly sensitive and selective for the detection of DCNP and DCP at a micromolar concentration within seconds with no observed interference from other various types of analytes. The LOD for 6b towards DCP was found to be 0.6 µM with a linear range from 0 to 8 µM. The low-cost portable cellulose paper strip fabricated with probe 6b for real-time detection of DCP in the gas phase and spiked water has been developed. The paper strip product was found effective in detecting the presence of DCP in water and vapor state with substantial color changes which could be easily observed by the naked eye and under a handheld UV lamp at a wavelength of 365 nm.

Visible-Light-Induced [1+5] Annulation of Phosphoryl Diazomethylarenes and Pyridinium 1,4-Zwitterionic Thiolates

Visible-light-induced [1+5] annulation of phosphoryl diazomethylarenes and pyridinium 1,4-zwitterionic thiolates generates various trifunctionalized dialkyl 1-phosphoryl-1,9a-dihydropyrido[2,1-c][1,4]thiazine-3,4-dicarboxylates in good to excellent yields and diastereoselectivities. The annulation involves the nucleophilic attack of thiolates on diazomethylarene-generated carbenes followed by an intramolecular cyclization, is free of catalysts, is atom-economical, and has mild reaction conditions.

Organic-Molecule-Based Fluorescent Chemosensor for Nerve Agents and Organophosphorus Pesticides

Organophosphorus (OP) compounds are typically a broad class of compounds that possess various uses such as insecticides, pesticides, etc. One of the most evil utilizations of these compounds is as chemical warfare agents, which pose a greater threat than biological weapons because of their ease of access. OP compounds are highly toxic compounds that cause irreversible inhibition of enzyme acetylcholinesterase, which is essential for hydrolysis of neurotransmitter acetylcholine, leading to series of neurological disorders and even death. Due to the extensive use of these organophosphorus compounds in agriculture, there is an increase in the environmental burden of these toxic chemicals, with severe environmental consequences. Hence, the rapid and sensitive, selective, real-time detection of OP compounds is very much required in terms of environmental protection, health, and survival. Several techniques have been developed over a few decades to easily detect them, but still, numerous challenges and problems remain to be solved. Major advancement has been observed in the development of sensors using the spectroscopic technique over recent years because of the advantages offered over other techniques, which we focus on in the presented review.