In-situ detoxification of schedule-I chemical warfare agents utilizing Zr(OH)4@W-ACF functional material for the development of next generation NBC protective gears.

Chemical warfare agents (CWAs) have become a pivotal concern for the global community and spurred a wide spectrum of research for the development of new generation protective materials. Herein, a highly effective self-detoxifying filter consisting of in-situ immobilized Zirconium hydroxide [Zr(OH)4] over woven activated carbon fabric [Zr(OH)4@W-ACF] is presented for the removal of CWAs. It was prepared to harness the synergistic effect of high surface area of W-ACF, leads to high dispersion of CWAs and high phosphilicity and reactivity of [Zr(OH)4]. The synthesized materials were characterized by ATR-FTIR, EDX, SEM, TEM, XPS, TGA, and BET surface area analyzer. The kinetics of  in-situ degradation of CWAs over Zr(OH)4@W-ACF were studied and found to be following the first-order reaction kinetics. The rate constant was found to be 0.244 min-1 and 2.31 × 10-2 min-1 for sarin and soman, respectively over Zr(OH)4@W-ACF. The potential practical applicability of this work was established by fabricating Zr(OH)4@W-ACF as reactive adsorbent layer for protective suit, and found to be meeting the specified criteria in terms of air permeability, tearing strength and nerve agent permeation as per TOP-08-2-501A:2013 and IS-17380:2020. The degradation products of CWAs were analyzed with NMR and GC-MS. The combined properties of dual functional textile with reactive material are expected to open up new exciting avenues in the field of CWAs protective clothing and thus find diverse application in defence and environmental sector.

In vivo protection studies of bis-quaternary 2-(hydroxyimino)- N-(pyridin-3-yl) acetamide derivatives against sarin poisoning in mice.

In vivo antidotal efficacy of new bis- quaternary 2-(hydroxyimino)- N-(pyridin-3yl) acetamide derivatives (HNK series), to counter multiples of lethal doses of nerve agent sarin (GB) and reactivation of acetylcholinesterase (AChE), was evaluated in Swiss albino mice. [Protection index PI; median lethal dose (LD50) of sarin with treatment/LD50 of sarin] was estimated, using 0.05, 0.10, and 0.20 LD50 as treatment doses of all the oximes with atropine against sarin poisoning. Dose-dependent time course study was conducted at 0.2, 0.4 and 0.8 LD50 dose of sarin for estimating maximum AChE inhibition. At optimized time (15 min), in vivo enzyme half inhibition concentration (IC50) was calculated. AChE reactivation efficacy of HNK series and pralidoxime (2-PAM) were determined by plotting shift of log IC50 doses. HNK-102 with atropine showed three fold higher PI compared to 2-PAM. In vivo IC50 of sarin for brain and serum AChE was found to be 0.87 LD50 (139.2 µg/kg) and 0.48 LD50 (77.23 µg/kg), respectively. Treatment with HNK-102 and HNK-111 (equal to their 0.20LD50) significantly reactivated sarin-intoxicated AChE ( p < 0.05) at 2× IC50 dose of sarin, compared to 2-PAM. The study revealed that HNK-102 oxime was three times more potent as antidote, for acute sarin poisoning compared to 2-PAM in vivo.

Synthesis and in vitro reactivation study of isonicotinamide derivatives of 2-(hydroxyimino)-N-(pyridin-3-yl)acetamide as reactivators of Sarin and VX inhibited human acetylcholinesterase (hAChE).

Previously (Karade et al., 2014), we have reported the synthesis and in vitro evaluation of bis-pyridinium derivatives of pyridine-3-yl-(2-hydroxyimino acetamide), as reactivators of sarin and VX inhibited hAChE. Few of the molecules showed superior in vivo protection efficacy (mice model) (Kumar et al., 2014; Swami et al., 2016) in comparison to 2-PAM against DFP and sarin poisoning. Encouraged by these results, herein we report the synthesis and in vitro evaluation of isonicotinamide derivatives of pyridine-3-yl-(2-hydroxyimino acetamide) (4a-4d) against sarin and VX inhibited erythrocyte ghost hAChE. Reactivation kinetics of these compounds was studied and the determined kinetic parameters were compared with that of commercial reactivators viz. 2-PAM and obidoxime. In comparison to 2-PAM and obidoxime, oxime 4a and 4b exhibited enhanced reactivation efficacy toward sarin inhibited hAChE while oxime 4c showed far greater reactivation efficacy toward VX inhibited hAChE. The acid dissociation constant and IC50 values of these oximes were determined and correlated with the observed reactivation potential.

Synthesis and in-vitro reactivation screening of imidazolium aldoximes as reactivators of sarin and VX-inhibited human acetylcholinesterase (hAChE).

Post-treatment of organophosphate (OP) poisoning involves the application of oxime reactivator as an antidote. Structurally different oximes are widely studied to examine their kinetic and mechanistic behavior against OP-inhibited cholinesterase enzyme. A series of structurally related 1,3-disubstituted-2-[(hydroxyiminomethyl)alkyl]imidazolium halides (5a-5e, 9a-9c) were synthesized and further evaluated for their in-vitro reactivation ability to reactivate sarin- and VX-inhibited human acetylcholinesterase (hAChE). The observed results were compared with the reactivation efficacy of standard reactivators; 2-PAM, obidoxime and HI-6. Amongst the synthesized oximes, 5a, 9a and 9b were found to be most potent reactivators against sarin-inhibited hAChE while in case of VX only 9a exhibited comparable reactivity with 2-PAM. Incorporation of pyridinium ring to the imidazole ring resulted in substantial increase in the reactivation strength of prepared reactivator. Physicochemical properties of synthesized reactivators have also been evaluated.

Oxime-mediated in vitro reactivation kinetic analysis of organophosphates-inhibited human and electric eel acetylcholinesterase.

Organophosphate (OP)-based pesticides and nerve agents are highly toxic compounds which interrupt the catalytic mechanism of acetylcholinesterase (AChE) by phosphorylating the hydroxyl moiety of serine residue. The inhibited enzyme can be reactivated by the nucleophilic action of oxime reactivators. To analyze the effect of different AChE sources on reactivation efficacy of reactivators, several in vivo studies have carried out using variety of AChE sources like pig, rat and monkey. Investigations on species differences provide a better insight for the development of new reactivators. Hence, present study was mainly targeted on comparative analysis of the reactivation of electric eel and human AChE inhibited by different OP. A series of butene-linked bis-pyridinium mono oximes which vary in functional groups present at the second pyridinium ring have been examined against sarin, VX, tabun and ethyl-paraoxon-poisoned AChE. In case of tabun-inhibited AChEs, tested oximes were better than reference oximes. For VX-poisoned human AChE, reactivator K251 (kr2;1.51 mM (-) (1 )min (-) (1)) showed good reactivation efficacy with standard oximes. Studies stipulated that butene-linked oximes consisting of different functional moieties are good reactivators and found to have better efficacy to reactivate nerve agent-inhibited human AChE in comparison to eel AChE.

Synthesis and in vitro kinetic evaluation of N-thiazolylacetamido monoquaternary pyridinium oximes as reactivators of sarin, O-ethylsarin and VX inhibited human acetylcholinesterase (hAChE).

Presently available medications for treatment of organiphosphorus poisoning are not sufficiently effective due to various pharmacological and toxicological reasons. In this regard, herein we report the synthesis of a series of N-thiazolylacetamide monoquaternary pyridinium oximes and its analogs (1a-1b to 6a-6b) with diversely substituted thiazole ring and evaluation of their in vitro reactivation efficacies against nerve agent (sarin, O-ethylsarin and VX) inhibited human erythrocyte acetylcholinesterase (hAChE). Reactivation kinetics was performed to determine dissociation constant (KD), reactivity rate constant (kr) and the second order rate constant (kr2) for all the compounds and compared their efficacies with commercial antidotes viz. 2-PAM and obidoxime. All the newly synthesized oximes were evaluated for their physicochemical parameters (pKa) and correlated with their respective reactivation efficacies to assess the capability of the oxime reactivator. Three of these novel compounds showed promising reactivation efficacies toward OP inhibited hAChE. Molecular docking studies were performed in order to correlate the reactivation efficacies with their interactions in the active site of the AChE.

Synthesis and in vitro kinetic study of novel mono-pyridinium oximes as reactivators of organophosphorus (OP) inhibited human acetylcholinesterase (hAChE).

A series of mono pyridinium oximes linked with arenylacetamides as side chains were synthesized and their in vitro reactivation potential was evaluated against human acetylcholinesterase (hAChE) inhibited by organophosphorus inhibitors (OP) such as sarin, VX and tabun. The reactivation data of the synthesized compounds were compared with those obtained with standard reactivators such as 2-PAM and obidoxime. The dissociation constant (KD) and specific reactivity (kr) of the oximes were also determined by performing reactivation kinetics against OP inhibited hAChE. Among the synthesized compounds, oximes 1-(2-(4-cyanophenylamino)-2-oxoethyl)-4-((hydroxyimino)methyl)pyridinium chloride (12a) and 4-((hydroxyimino)methyl)-1-(2-(4-methoxyphenylamino)-2-oxoethyl)pyridinium chloride (2a) were found most potent reactivators for hAChE inhibited by sarin. In case of VX inhibited hAChE majority of the oximes have shown good reactivation efficacies. Among these oximes 1-(2-(benzylamino)-2-oxoethyl)-4-((hydroxyimino)methyl)pyridinium chloride (18a), 4-((hydroxyimino)methyl)-1-(2-(4-(methoxycarbonyl)phenylamino)-2-oxoethyl)pyridinium-chloride (14a) and 12a were found to surpass the reactivation potential of 2-PAM and obidoxime. However, the synthesized oximes showed marginal reactivation efficacies in case of tabun inhibited hAChE. The pKa value of the oximes were determined and correlated with their observed reactivation potential.

Controlled release studies of antimalarial 1, 3, 5-trisubstituted-2-pyrazolines from biocompatible chitosan-heparin Layer-by-Layer (LbL) self assembled thin films.

Herein we report the in-vitro controlled release properties of 1, 3, 5-trisubstituted-2-pyrazolines through Layer-by-Layer (LbL) self assembled thin films fabricated from chitosan and heparin sodium salt as biocompatible polyelectrolytes. This study was carried out as a preliminary step towards the applicability of LbL technique in prophylactic drug delivery of antimalarial drugs. The growth of LbL self assembly was monitored by UV-Visible spectrophotometry and Quartz Crystal Microbalance (QCM). The loading as well as in-vitro release studies (in phosphate buffer saline at pH 7.4) were carried out using UV-Visible spectroscopy. Three compounds having good antimalarial activity were tested and the release rate was found inversely proportional to the hydrophobicity of the drug. Pzln-4 has shown best release among all the three compounds (up to 780 min) followed by Pzln-5 and Pzln-8. The release trend was that of a fast release up to first 2 h followed by a steady release. Kinetic fitting of the data confirmed the process of drug release followed a pseudo second order kinetics (R(2)≥0.99). A large value of rate constant (k) revealed a faster release. Pzln-4 has shown smallest value of k corresponding to slowest release among all the three compounds.

Assessment of antidotal efficacy of cholinesterase reactivators against paraoxon: In vitro reactivation kinetics and physicochemical properties.

The search of proficient oximes as reactivators of irreversibly inhibited-AChE by organophosphate poisoning necessitates an appropriate assessment of their physicochemical properties and reactivation kinetics. Therefore, herein acid dissociation constant; pKa, lipophilicity; logP, polar surface area, hydrogen bond donor and acceptor counts of structurally different oximes (two tertiary oximes and thirteen pyridinium aldoxime derivatives) have been evaluated. The experimentally obtained data for pKa has been comparatively analyzed by using non-linear regression. Further the tested oximes were screened through in vitro reactivation kinetics against paraoxon-inhibited AChE. The pKa values of all the examined oximes were within the range of 7.50-9.53. pKa values of uncharged and mono-pyridinium oximes were in good correlation with their reactivation potency. The high negative logP values of pyridinium oxime reactivators indicate their high hydrophilic character; hence oximes with improved lipophilicity should be designed for the development of novel and more potent antidotes. Propane and butane linked oximes were superior reactivators than xylene linked bis-oxime reactivators. It is concluded from the present study that pKa value is not only ruled by the position of oximino functionality in the pyridinium ring, but also by the position of linker. Although, pyridinium oximes are proved to be better reactivators but their lipophilicity has to be improved.

Synthesis and in vitro evaluation of bis-quaternary 2-(hydroxyimino)-N-(pyridin-3-yl)acetamide derivatives as reactivators against sarin and VX inhibited human acetylcholinesterase (hAChE).

A series of bis-quaternary pyridinium derivatives 3a-3i of 2-(hydroxyimino)-N-(pyridin-3-yl)acetamide (2) have been synthesized. The synthesized pyridinium compounds have an amide group in conjugation to the oxime moiety. These compounds were evaluated in vitro for their reactivation efficacy against organophosphorus (OP) nerve agents (NAs) (sarin and VX) inhibited human erythrocyte ghost acetylcholinesterase (hAChE) and compared with the reactivation efficacy of 2-PAM and obidoxime. The pKa values of the synthesized compounds were found closer to the pKa values of 2- and 4-pyridinium oxime reactivators such as 2-PAM and obidoxime. Some of the compounds have shown better reactivation efficacy than 2-PAM, and obidoxime against sarin and VX inhibited AChE.

In vitro reactivation potency of novel symmetrical bis-pyridinium oximes for electric eel acetylcholinesterase inhibited by nerve agent sarin.

This communication describes synthesis and in vitro evaluation of a series of novel bis-pyridinium oximes connected by bis-methoxymethyl benzene, 1,4-bis-methoxymethyl (cis)-but-2-ene and 1,4-bis-methoxymethyl but-2-yne linkers as reactivators of sarin inhibited acetylcholinesterase (AChE). The reactivation data of synthesized oximes were compared with those of 2-PAM and obidoxime. The efficacy of oximes such as 1,4-dimethoxy cis-but-2-ene bis-[4,4'-(hydroxyiminomethyl)-pyridinium] dichloride (3g), 1,4-dimethoxy benzene bis-[3,3'-(hydroxyimino-methyl) pyridinium] dichloride (3b) and 1,3-dimethoxy benzene bis-[3,3'-(hydroxy-iminomethyl) pyridinium] dichloride (3e) were found to be more than that of obidoxime in reactivating sarin inhibited AChE. The oxime 3g was able to reactivate 25% of AChE activity in comparison to 20% and 5% reactivation exhibited by 2-PAM and obidoxime respectively at a concentration of 10(-4) M. The pKa of the oximes were determined and correlated with the reactivation potential.

Synthesis and in vitro evaluation of xylene linked carbamoyl bis-pyridinium monooximes as reactivators of organophosphorus (OP) inhibited electric eel acetylcholinesterase (AChE).

A series of carbamoyl bis-pyridinium monooximes linked with xylene linker were synthesized and their in-vitro reactivation potential was evaluated against acetylcholinesterase (AChE) inhibited by organophosphorus inhibitors (OP) such as sarin, DFP and VX and the data were compared with reactivation obtained with 2-PAM and obidoxime. Amongst the synthesized compounds, 3-carbamoyl-2'hydroxyiminomethyl-1-1'-(1,4-phenylenedimethyl)-bispyridinium dibromide (5e) 3-carbamoyl-2'hydroxyiminomethy l-1-1'-(1,3-phenylenedimethyl)-bispyridinium dibromide (5k) and 4-carbamoyl-2'hydroxyiminomethyl-1-1'-(1,3-phenylenedimethyl)-bispyridinium dibromide (5l) were found to be the most potent reactivators for electric eel AChE inhibited by sarin and DFP. However, in case of VX inhibited AChE, none of the synthesized oximes could surpass the reactivation potential of 2-PAM and obidoxime. The pKa values of all the oximes were determined and correlated with their observed reactivation potential.

In vitro reactivation of sarin-inhibited human acetylcholinesterase (AChE) by bis-pyridinium oximes connected by xylene linkers.

A series of bis-pyridinium oximes connected by xylene linkers were synthesized and their in vitro reactivation potential was evaluated against human acetylcholinesterase (hAChE) inhibited by nerve agent sarin and the data were compared with 2-PAM and obidoxime. Among the synthesized compounds, N,N'-p-xylene-bis-[(2,2'-hydroxyiminomethyl)pyridinium] dibromide (3c) was found to be the most potent reactivator for hAChE inhibited by sarin. The oxime 3c exhibited 45% regeneration of inhibited hAChE, in comparison to 34% and 24% regeneration by 2-PAM and obidoxime, respectively, at a concentration of 10(-3) M within 10 min. The higher reactivation efficacies of these oximes were attributed to their acid dissociation constants (pKa). The pKa values of all the oximes were determined spectrophotometrically and correlated with their observed reactivation potential. This method involving the in vitro reactivation of inhibited hAChE may be useful for the screening of new oximes as reactivators.

In vitro evaluation of bis-pyridinium oximes bearing methoxy alkane linker as reactivators of sarin inhibited human acetylcholinesterase.

A series of bis-pyridinium oximes connected by methoxy alkane linkers were synthesized and their in vitro reactivation efficacy was evaluated against sarin-inhibited human AChE, and data were compared with 2-PAM and obidoxime. Among the synthesized compounds, 1,2-dimethoxy ethylene bis-[4,4'-(hydroxyiminomethyl) pyridinium] dichloride (4P-2) and 1,2-dimethoxy ethylene bis-[3,3'-(hydroxyiminomethyl) pyridinium] dichloride (3P-2) were found to be the most potent reactivators of human AChE inhibited by nerve agent sarin. The oximes 4P-2 and 3P-2 exhibited 41% and 36% regeneration of sarin-inhibited AChE, respectively, whereas 2-PAM showed 32% regeneration. The higher reactivation efficacy of the oximes was attributed to their acid dissociation constants (pK(a)). The pK(a) values of all the oximes were determined by UV-vis spectrophotometric method and correlated with their observed reactivation potential. Overall, the study reveals that the oxime 4P-2 may have therapeutic potential in the reactivation of human AChE inhibited by sarin.

Synthesis and evaluation of novel bis-pyridinium oximes as reactivators of DFP-inhibited acetylcholinesterase.

A series of novel bis-pyridinium oximes connected by bis-methoxymethyl benzene, 1,4-bis-methoxymethyl (cis)-but-2-ene and 1,4-bis-methoxymethyl but-2-yne linkers were synthesized and their in vitro reactivation efficacy was evaluated against diisopropyl phosphorofluoridate (DFP) inhibited acetylcholinesterase (AChE) and compared with the established antidote 2-PAM and obidoxime. However, the best reactivation was observed with the standard oxime 2-PAM. The reactivation efficacy of 1,3-dimethoxymethyl benzene bis-[4,4'-(hydroxyiminomethyl) pyridinium] dichloride (3d) and 1,4-dimethoxy but-2-ene bis-[4,4'-(hydroxyiminomethyl) pyridinium] dichloride (3g) was comparable with that of obidoxime, another standard antidote.

In-vitro regeneration of sarin inhibited electric eel acetylcholinesterase by bis-pyridinium oximes bearing xylene linker.

A series of bis-pyridinium oximes connected by xylene linker were synthesized and their in-vitro reactivation potential was evaluated against acetylcholinesterase (AChE) inhibited by nerve agent, sarin. Among the synthesized compounds, alpha,alpha'xylene-bis-[3,3'-(hydroxyiminomethyl) pyridinium] dibromide (3b) was found to be most potent reactivator for AChE inhibited by sarin. The oxime 3b exhibits 34% regeneration of inhibited AChE, in comparison to 20 and 15% regeneration by 2-PAM and obidoxime, respectively, at a concentration of 10(-4) M within 10 min.

In vitro reactivation of sarin inhibited electric eel acetylcholinesterase by bis-pyridinium oximes bearing methoxy ether linkages.

Bis-pyridinium oximes connected by methoxy alkane ether linker were synthesized and their in vitro reactivation efficacy was evaluated for sarin inhibited AChE. Reactivation efficacy of synthesized compounds was compared with 2-PAM and obidoxime. Among the synthesized compounds, 1,2-dimethoxy ethylene bis-[3,3'-(hydroxyiminomethyl) pyridinium] dichloride (3P-2) and 1,3-dimethoxy propylene bis-[3,3'-(hydroxyiminomethyl) pyridinium] dichloride (3P-3) were found to be most potent reactivators for AChE inhibited by nerve agent sarin. 3P-2 and 3P-3, respectively exhibited 80% and 69% regeneration of inhibited AChE, whereas 2-PAM (well known antidote for nerve agent poisoning) showed 42% regeneration.