Generic placeholder image

Medicinal Chemistry


ISSN (Print): 1573-4064
ISSN (Online): 1875-6638

Research Article

Synthesis, Molecular Docking, BSA, and In Vitro Reactivation Study of Imidazopyridine Oximes Against Paraoxon Inhibited Acetylcholinesterase

Author(s): Ashima Thakur, Jayant Patwa, Abha Sharma* and Swaran Jeet Singh Flora*

Volume 18 , Issue 2 , 2022

Published on: 08 February, 2021

Page: [273 - 287] Pages: 15

DOI: 10.2174/1573406417666210208223240


Aim: To synthesize and evaluate the fused heterocyclic imidazo[1,2-a]pyridine based oxime as a reactivator against paraoxon inhibited acetylcholinesterase.

Background: Organophosphorus compounds (OPs) include parathion, malathion, chlorpyrifos, monocrotophos, and diazinon, which are commonly used in agriculture for enhancing agricultural productivity via killing crop-damaging pests. However, people may get exposed to OPs pesticides unintentionally/intentionally via ingestion, inhalation, or dermal. The current treatment regimen includes reactivator such as mono or bis-pyridinium oximes along with anticholinergic and anticonvulsant drugs that are recommended for the treatment of OP poisoning. Unfortunately, the drawback of the existing reactivator is the permanent charge present on the pyridinium, making them inefficient to cross the blood-brain barrier (BBB) and reactivate OP-inhibited central nervous system (CNS) acetylcholinesterase. Therefore, there is a need of a reactivator that could cross the BBB and reactivate the OP inhibited acetylcholinesterase.

Objective: The objectives of the study were synthesis, molecular docking, BSA binding, and in-vitro estimation of oximes of various substituted imidazo [1,2-a]pyridine against paraoxon inhibited acetylcholinesterase.

Methods: The reactivators were synthesized in three steps and characterized using various spectroscopic techniques. The molecular docking study was performed on 2WHP and 3ZLV PDB using the Glide-XP software. The acid dissociation constant (pKa) of oximes was calculated experimentally, and the drug-likeness properties of the oximes were calculated in silico using Molinspiration and Swiss ADME software. The binding of oximes with bovine serum albumin (BSA) was also investigated using a Fluorescence spectrophotometer. The reactivation potential of the oximes was determined by in vitro enzymatic assay.

Results: The In-silico study inferred that the synthesized molecules fulfilled the parameters required for a successful CNS drug candidate. Furthermore, in-vitro enzymatic assay indicated reasonable reactivation potential of the oximes against paraoxon-inhibited AChE. The binding of oximes with bovine serum albumin (BSA) revealed that there was a static quenching of intrinsic fluorescence of BSA by the oxime. The binding constant value and number of binding sites were found to be 0.24 x 104 mol-1 and 1, respectively.

Conclusion: The results of the study concluded that this scaffold could be used for further designing of more efficient uncharged reactivators.

Keywords: Acetylcholinesterase, imidazopyridine oxime, organophosphorous, obidoxime, 2-PAM, [1, 2-a]pyridine.

Graphical Abstract
Santoni, G.; de Sousa, J.; de la Mora, E.; Dias, J.; Jean, L.; Sussman, J.L.; Silman, I.; Renard, P.Y.; Brown, R.C.D.; Weik, M.; Baati, R.; Nachon, F. Structure-based optimization of nonquaternary reactivators of acetylcholinesterase inhibited by organophosphorus nerve agents. J. Med. Chem., 2018, 61(17), 7630-7639.
[] [PMID: 30125110]
Delfino, R.T.; Ribeiro, T.S.; Figueroa-Villar, J.D. Organophosphorus compounds as chemical warfare agents: a review. J. Braz. Chem. Soc., 2009, 20(3), 407-428.
Silman, I.; Sussman, J.L. Acetylcholinesterase: ‘classical’ and ‘non-classical’ functions and pharmacology. Curr. Opin. Pharmacol., 2005, 5(3), 293-302.
[] [PMID: 15907917]
Marrs, T.C. Organophosphate poisoning. Pharmacol. Ther., 1993, 58(1), 51-66.
[] [PMID: 8415873]
Nagao, M.; Takatori, T.; Matsuda, Y.; Nakajima, M.; Iwase, H.; Iwadate, K. Definitive evidence for the acute sarin poisoning diagnosis in the Tokyo subway. Toxicol. Appl. Pharmacol., 1997, 144(1), 198-203.
[] [PMID: 9169085]
Bajgar, J. Organophosphates/nerve agent poisoning: mechanism of action, diagnosis, prophylaxis, and treatment. Adv. Clin. Chem., 2004, 38, 151-216.
[] [PMID: 15521192]
Jokanović, M.; Prostran, M. Pyridinium oximes as cholinesterase reactivators. Structure-activity relationship and efficacy in the treatment of poisoning with organophosphorus compounds. Curr. Med. Chem., 2009, 16(17), 2177-2188.
[] [PMID: 19519385]
Bajgar, J.; Fusek, J.; Kuca, K.; Bartosova, L.; Jun, D. Treatment of organophosphate intoxication using cholinesterase reactivators: facts and fiction. Mini Rev. Med. Chem., 2007, 7(5), 461-466.
[] [PMID: 17504181]
Lorke, D.E.; Kalasz, H.; Petroianu, G.A.; Tekes, K. Entry of oximes into the brain: a review. Curr. Med. Chem., 2008, 15(8), 743-753.
[] [PMID: 18393843]
Shih, T.M.; Skovira, J.W.; O’Donnell, J.C.; McDonough, J.H. In vivo reactivation by oximes of inhibited blood, brain and peripheral tissue cholinesterase activity following exposure to nerve agents in guinea pigs. Chem. Biol. Interact., 2010, 187(1-3), 207-214.
[] [PMID: 20223229]
Little, P.J.; Scimeca, J.A.; Martin, B.R. Distribution of [3H]diisopropylfluorophosphate, [3H]soman, [3H]sarin, and their metabolites in mouse brain. Drug Metab. Dispos., 1988, 16(4), 515-520.
[PMID: 2903016]
DiGiovanni, C., Jr Domestic terrorism with chemical or biological agents: psychiatric aspects. Am. J. Psychiatry, 1999, 156(10), 1500-1505.
[] [PMID: 10518158]
Pankow, D.; Jagielki, S. Effect of methanol or modifications of the hepatic glutathione concentration on the metabolism of dichloromethane to carbon monoxide in rats. Hum. Exp. Toxicol., 1993, 12(3), 227-231.
[] [PMID: 8100433]
Radić, Z.; Sit, R.K.; Kovarik, Z.; Berend, S.; Garcia, E.; Zhang, L.; Amitai, G.; Green, C.; Radić, B.; Fokin, V.V.; Sharpless, K.B.; Taylor, P. Refinement of structural leads for centrally acting oxime reactivators of phosphylated cholinesterases. J. Biol. Chem., 2012, 287(15), 11798-11809.
[] [PMID: 22343626]
Shih, T.M.; Skovira, J.W.; O'Donnell, J.C.; McDonough, J.H. Treatment with tertiary oximes prevents seizures and improves survival following sarin intoxication.Journal of molecular neuroscience : MN, 2010, 40(1-2), 63-69.,
Kalisiak, J.; Ralph, E.C.; Zhang, J.; Cashman, J.R. Amidine-oximes: reactivators for organophosphate exposure. J. Med. Chem., 2011, 54(9), 3319-3330.
[] [PMID: 21438612]
Kalisiak, J.; Ralph, E.C.; Cashman, J.R. Nonquaternary reactivators for organophosphate-inhibited cholinesterases. J. Med. Chem., 2012, 55(1), 465-474.
[] [PMID: 22206546]
Kuca, K.; Juna, D.; Musilek, K. Structural requirements of acetylcholinesterase reactivators. Mini Rev. Med. Chem., 2006, 6(3), 269-277.
[] [PMID: 16515465]
Saxena, A.; Singh, B.; Sharma, A.; Dubey, V.; Semwal, R.P.; Suryanarayana, M.V.; Rao, V.K.; Sekhar, K. Adsorption of dimethyl methylphosphonate on metal impregnated carbons under static conditions. J. Hazard. Mater., 2006, 134(1-3), 104-111.
[] [PMID: 16343758]
Sharma, A.; Singh, B.; Saxena, A. Polyoxometalate impregnated carbon systems for the in situ degradation of sulphur mustard. Carbon, 2009, 47(8), 1911-1915.
Sharma, A.; Saxena, A.; Singh, B. In-situ degradation of sulphur mustard using (1R)-(-)-(camphorylsulphonyl) oxaziridine impregnated adsorbents. J. Hazard. Mater., 2009, 172(2-3), 650-653.
[] [PMID: 19674836]
Sharma, R.; Gupta, B.; Sahu, A.K.; Acharya, J.; Satnami, M.L.; Ghosh, K.K. Synthesis and in-vitro reactivation screening of imidazolium aldoximes as reactivators of sarin and VX-inhibited human acetylcholinesterase (hAChE). Chem. Biol. Interact., 2016, 259(Pt B), 85-92.,
[] [PMID: 27138243]
Soukup, O.; Korabecny, J.; Malinak, D.; Nepovimova, E.; Pham, N.L.; Musilek, K.; Hrabinova, M.; Hepnarova, V.; Dolezal, R.; Pavek, P.; Jost, P.; Kobrlova, T.; Jankockova, J.; Gorecki, L.; Psotka, M.; Nguyen, T.D.; Box, K.; Outhwaite, B.; Ceckova, M.; Sorf, A.; Jun, D.; Kuca, K. In vitro and in silico Evaluation of Non-Quaternary Reactivators of AChE as Antidotes of Organophosphorus Poisoning - a New Hope or a Blind Alley? Med. Chem., 2018, 14(3), 281-292.
[] [PMID: 29332594]
Patel, C.; Thakur, A.; Pereira, G.; Sharma, A. Gluconic acid promoted cascade reactions of 2-phenylimidazo[1,2-a] pyridine-3-carbaldehyde with cyclohexane-1,3-dione to create novel fused bisheterocycles. Synth. Commun., 2019, 49(14), 1836-1846.
Aggarwal, S.; Tiwari, A.; Kumar, V.; Pratap, R.; Singh, G.; Mishra, A. Novel pyridinium oximes: synthesis, molecular docking and in vitro reactivation studies. RSC Advances, 2015, 5(30), 23471-23480.
Thakur, A.; Pereira, G.; Patel, C.; Chauhan, V.; Dhaked, R.; Sharma, A. Design, one-pot green synthesis and antimicrobial evaluation of novel imidazopyridine bearing pyran bis-heterocycles. J. Mol. Struct., 2020, 1206127686
Ellman, G.L.; Courtney, K.D.; Andres, V., Jr; Feather-Stone, R.M. A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem. Pharmacol., 1961, 7, 88-95.
[] [PMID: 13726518]
Patwa, J.; Thakur, A.; Sharma, A.; Flora, S.J.S. Monoisoamyl DMSA reduced copper-induced neurotoxicity by lowering 8-OHdG level, amyloid beta and Tau protein expressions in Sprague-Dawley rats. Metallomics, 2020, 12(9), 1428-1448.
[] [PMID: 32677644]
Singh, S.; Sharda, N.; Mahajan, L. Spectrophotometric determination of pKa of nimesulide. Int. J. Pharm., 1999, 176(2), 261-264.
[] [PMID: 10370196]
Lipinski, C.; Lipinski, C.A. Lead- and drug-like compounds: the rule-of-five revolution. Drug Discov. Today Technol. 1, 337-341. Drug Discov. Today. Technol., 2004, 1, 337-341.
[] [PMID: 24981612]
Clark, D.E. Rapid calculation of polar molecular surface area and its application to the prediction of transport phenomena. 2. Prediction of blood-brain barrier penetration. J. Pharm. Sci., 1999, 88(8), 815-821.
[] [PMID: 10430548]
Hitchcock, S.A.; Pennington, L.D. Structure-brain exposure relationships. J. Med. Chem., 2006, 49(26), 7559-7583.
[] [PMID: 17181137]
Pajouhesh, H.; Lenz, G.R. Medicinal chemical properties of successful central nervous system drugs. NeuroRx: J. Am. Soc. Exp. NeuroTher., 2005, 2(4), 541-553.
Ekström, F.; Hörnberg, A.; Artursson, E.; Hammarström, L.G.; Schneider, G.; Pang, Y.P. Structure of HI-6*sarin-acetylcholinesterase determined by X-ray crystallography and molecular dynamics simulation: reactivator mechanism and design. PLoS One, 2009, 4(6)e5957
[] [PMID: 19536291]
Farid, R.; Day, T.; Friesner, R.A.; Pearlstein, R.A. New insights about HERG blockade obtained from protein modeling, potential energy mapping, and docking studies. Bioorg. Med. Chem., 2006, 14(9), 3160-3173.
[] [PMID: 16413785]
Reddy, D.S.; Kongot, M.; Netalkar, S.P.; Kurjogi, M.M.; Kumar, R.; Avecilla, F.; Kumar, A. Synthesis and evaluation of novel coumarin-oxime ethers as potential anti-tubercular agents: Their DNA cleavage ability and BSA interaction study. Eur. J. Med. Chem., 2018, 150, 864-875.
[] [PMID: 29597169]
Ribeiro, T.S.; Prates, A.; Alves, S.R.; Oliveira-Silva, J.J.; Riehl, C.A.; Figueroa-Villar, J.D. The effect of neutral oximes on the reactivation of human acetylcholinesterase inhibited with paraoxon. J. Braz. Chem. Soc., 2012, 23(7), 1216-1225.
Palanimuthu, D.; Poon, R.; Sahni, S.; Anjum, R.; Hibbs, D.; Lin, H.Y.; Bernhardt, P.V.; Kalinowski, D.S.; Richardson, D.R. A novel class of thiosemicarbazones show multi-functional activity for the treatment of Alzheimer’s disease. Eur. J. Med. Chem., 2017, 139, 612-632.
[] [PMID: 28841514]
Voicu, V.A.; Bajgar, J.; Medvedovici, A.; Radulescu, F.S.; Miron, D.S. Pharmacokinetics and pharmacodynamics of some oximes and associated therapeutic consequences: a critical review. J. Appl. Toxicol., 2010, 30(8), 719-729.
[] [PMID: 20635332]
Lipinski, C.A.; Lombardo, F.; Dominy, B.W.; Feeney, P.J. Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings. Adv. Drug Deliv. Rev., 2001, 46(1-3), 3-26.
[] [PMID: 11259830]
Rankovic, Z. CNS drug design: balancing physicochemical properties for optimal brain exposure. J. Med. Chem., 2014, 58(6), 2584-2608.
[PMID: 25494650]
Albert, A. The determination of ionization constants: a laboratory manual; Springer Science & Business Media, 2012.
Musil, K.; Florianova, V.; Bucek, P.; Dohnal, V.; Kuca, K.; Musilek, K. Development and validation of a FIA/UV-vis method for pK(a) determination of oxime based acetylcholinesterase reactivators. J. Pharm. Biomed. Anal., 2016, 117, 240-246.
[] [PMID: 26386953]
Sharma, R.; Gupta, B.; Sahu, A.K.; Acharya, J.; Satnami, M.L.; Ghosh, K.K. Synthesis and in-vitro reactivation screening of imidazolium aldoximes as reactivators of sarin and VX-inhibited human acetylcholinesterase (hAChE). Chemico-biological interactions, 2016, 259(B), 85-92.,
Chennamaneni, S.R.; Vobalaboina, V.; Garlapati, A. Quaternary salts of 4,3′ and 4,4′ bis-pyridinium monooximes: synthesis and biological activity. Bioorg. Med. Chem. Lett., 2005, 15(12), 3076-3080.
[] [PMID: 15908205]
Kassa, J. Review of oximes in the antidotal treatment of poisoning by organophosphorus nerve agents. J. Toxicol. Clin. Toxicol., 2002, 40(6), 803-816.
[] [PMID: 12475193]
Musilek, K.; Kuca, K.; Jun, D.; Dohnal, V.; Dolezal, M. Synthesis of a novel series of bispyridinium compounds bearing a xylene linker and evaluation of their reactivation activity against chlorpyrifos-inhibited acetylcholinesterase. J. Enzyme Inhib. Med. Chem., 2005, 20(5), 409-415.
[] [PMID: 16335048]
Kuca, K.; Cabal, J.; Jun, D.; Musilek, K. In vitro reactivation potency of acetylcholinesterase reactivators--K074 and K075--to reactivate tabun-inhibited human brain cholinesterases. Neurotox. Res., 2007, 11(2), 101-106.
[] [PMID: 17449453]
Bajgar, F.; Jakl, A.; Hrdina, V. Influence of trimedoxime and atropine on acetylcholinesterase activity in some parts of the brain of mice poisoned by isopropylmethyl phosphonofluoridate. Biochem. Pharmacol., 1971, 20(11), 3230-3233.
[] [PMID: 5132126]
Bajgar, J.; Jakl, A.; Hrdina, V. The influence of obidoxime on acetylcholinesterase activity in different parts of the mouse brain following isopropylmethyl phosphonofluoridate intoxication. Eur. J. Pharmacol., 1972, 19(2), 199-202.
[] [PMID: 5071791]
Eyer, P. The role of oximes in the management of organophosphorus pesticide poisoning. Toxicol. Rev., 2003, 22(3), 165-190.
[] [PMID: 15181665]
Kongot, M.; Maurya, N.; Dohare, N.; Parray, M.U.D.; Maurya, J.K.; Kumar, A.; Patel, R. Enthalpy-driven interaction between dihydropyrimidine compound and bovine serum albumin: a spectroscopic and computational approach. J. Biomol. Struct. Dyn., 2018, 36(5), 1161-1170.
[] [PMID: 28399704]
Sood, D.; Kumar, N.; Rathee, G.; Singh, A.; Tomar, V.; Chandra, R. Mechanistic Interaction Study of Bromo-Noscapine with Bovine Serum Albumin employing Spectroscopic and Chemoinformatics Approaches. Sci. Rep., 2018, 8(1), 16964.
[] [PMID: 30446713]
Rahman, Y.; Afrin, S.; Tabish, M. Interaction of pirenzepine with bovine serum albumin and effect of β-cyclodextrin on binding: A biophysical and molecular docking approach. Arch. Biochem. Biophys., 2018, 652, 27-37.
[] [PMID: 29908138]

© 2022 Bentham Science Publishers | Privacy Policy