Effect of different oximes on rat and human cholinesterases inhibited by methamidophos: a comparative in vitro and in silico study.

Methamidophos is one of the most toxic organophosphorus (OP) compounds. It acts via phosphorylation of a serine residue in the active site of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), leading to enzyme inactivation. Different oximes have been developed to reverse this inhibition. Thus, our work aimed to test the protective or reactivation capability of pralidoxime and obidoxime, as well as two new oximes synthesised in our laboratory, on human and rat cholinesterases inhibited by methamidophos. In addition, we performed molecular docking studies in non-aged methamidophos-inhibited AChE to understand the mechanisms involved. Our results suggested that pralidoxime protected and reactivated methamidophos-inhibited rat brain AChE. Regarding human erythrocyte AChE, all oximes tested protected and reactivated the enzyme, with the best reactivation index observed at the concentration of 50 µM. Concerning BChE, butane-2,3-dionethiosemicarbazone oxime (oxime 1) was able to protect and reactivate the methamidophos-inhibited BChE by 45% at 50 µM, whereas 2(3-(phenylhydrazono)butan-2-one oxime (oxime 2) reactivated 28% of BChE activity at 100 µM. The two classical oximes failed to reactivate BChE. The molecular docking study demonstrated that pralidoxime appears to be better positioned in the active site to attack the O-P moiety of the inhibited enzyme, being near the oxyanion hole, whereas our new oximes were stably positioned in the active site in a manner similar to that of obidoxime. In conclusion, our work demonstrated that the newly synthesised oximes were able to reactivate not only human erythrocyte AChE but also human plasma BChE, which could represent an advantage in the treatment of OP compounds poisoning.

4-Methyl-N'-(2-oxoindolin-3-yl-idene)benzene-1-sulfono-hydrazide.

In the title compound, C(15)H(13)N(3)O(3)S, the C-S-N(H)-N linkage is non-planar, the torsion angle being -65.12 (13)° and the S atom showing a tetra-hedral environment. The compound has two almost planar fragments linked to the S atom: the isatin-derivative fragment [(C(8)H(5)NO)N-N(H)-] and the tolyl fragment [C(7)H(7)-] have maximum deviations from the mean plane through the non-H atoms of 0.0813 (13) and 0.0094 (16) Å, respectively, and make an inter-planar angle of 80.48 (3)°. In the crystal, mol-ecules are connected into inversion dimers via pairs of N-H⋯O hydrogen bonds. Additionally, the mol-ecular structure is stabilized by an intra-molecular N-H⋯O hydrogen bond.

Potential of two new oximes in reactivate human acetylcholinesterase and butyrylcholinesterase inhibited by organophosphate compounds: an in vitro study.

Organophosphate (OP) compounds exert inhibition on cholinesterase (ChE) activity by irreversibly binding to the catalytic site of the enzyme. Oximes are compounds generally used to reverse the ChE inhibition caused by OP agents. In this study, we compared the in vitro reactivation potency of two new oximes (oxime 1: butane-2,3-dionethiosemicarbazone; oxime 2: 3-(phenylhydrazono) butan-2-one) against the inhibition on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities induced by chlorpyrifos, diazinon and malathion. Oximes used clinically (obidoxime and pralidoxime) were used as positive control. For this study, human blood (erythrocytes for AChE determination and plasma for BChE determination) was used and different concentrations of oximes (1-100 µM) were tested. The concentrations of OP used were based on the IC50 for AChE and BChE. Results demonstrated that obidoxime was more effective in reactivate the AChE inhibition induced by OP compounds. However, both newly developed oximes achieved similar reactivations rates that pralidoxime for chlorpyrifos and diazinon-inhibited AChE. For BChE reactivation, none of evaluated oximes achieved positives rates of reactivation, been obidoxime able to reactivate malathion-inhibited BChE only in 24% at the highest concentration. We conclude that both newly developed oximes seem to be promising reactivators of OP-inhibited AChE.

1-(5-Bromo-2-oxoindolin-3-yl-idene)thio-semicarbazide acetonitrile monosolvate.

In the crystal structure of the title compound, C(9)H(7)BrN(4)OS·C(2)H(3)N, the mol-ecules are connected via N-H⋯O and N-H⋯S inter-actions into zigzag chains perpendicular to [001]. The mol-ecules in these chains are additionally linked to acetonitrile solvent mol-ecules through N-H⋯N hydrogen bonding. The mol-ecules are arranged in layers and are stacked in the direction of the c axis indicative of π-π inter-actions, with distance = 3.381 (7) Šfor the C⋯C interaction parallel to [001]. An intra-molecular N-H⋯O hydrogen bond is also observed in the main mol-ecule.

Butane-2,3-dionethiosemicarbazone: an oxime with antioxidant properties.

Oximes are compounds generally used to reverse the acetylcholinesterase (AChE) inhibition caused by organophosphates (OPs). The aim of this study was to examine the capacity of the butane-2,3-dionethiosemicarbazone oxime to scavenge different forms of reactive species (RS) in vitro, as well as counteract their formation. The potential antioxidant and toxic activity of the oxime was assayed both in vitro and ex vivo. The obtained results indicate a significant hydrogen peroxide (H2O2), nitric oxide (NO) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity at 0.275, 0.5 and 5microM of oxime, respectively (p< or =0.05). The oxime exhibited a powerful inhibitory effect on dihydroxybenzoate formation (25microM) (p< or =0.05) and also decreased deoxyribose degradation induced by Fe2+ and via Fenton reaction (0.44 and 0.66mM, respectively) (p< or =0.05). The oxime showed a significant inhibitory effect on sigma-phenantroline reaction with Fe2+ (0.4mM) suggesting a possible interaction between the oxime and iron. A significant decrease in the basal and pro-oxidant-induced lipid peroxidation in brain, liver, and kidney of mice was observed both in vitro and ex vivo (p< or =0.05). In addition, in our ex vivo experiments the oxime did not depict any significant changes in thiol levels of liver, kidney and brain as well as did not modify the delta-aminolevulinate dehydratase (delta-ALA-D) activity in these tissues. Taken together our results indicate an in vitro and ex vivo antioxidant activity of the oxime possibly due to its scavenging activity toward different RS and a significant iron interaction.

Oximes as inhibitors of low density lipoprotein oxidation.

AIMS: Several lines of evidence support the hypothesis that the oxidation of low density lipoprotein (LDL) may play a crucial role in the initiation and progression of atherosclerosis. Various studies have shown a positive effect of antioxidant compounds on oxidative modification of LDL and atherogenesis. In view of this, we have investigated the possible antioxidant activity of two new oximes against Cu2+- induced LDL and serum oxidation. Oximes are used in organophosphate (OP) poisoning acting by restoring the cholinesterase function. However, their antioxidant capacities are not well understood and poorly studied. MAIN METHODS: We measured, in a Cu2+-induced oxidation, the conjugated dienes formation in serum and LDL and the loss of tryptophan fluorescence as well as the TBARS formation in the LDL. KEY FINDINGS: Our results showed that both oximes act as antioxidant and they are able to prevent LDL oxidation in a concentration-dependent manner. When human LDL or serum was oxidized by Cu2+, our oximes showed a significant increase in the lag phase of conjugated dienes and a significant decrease in the thiobarbituric acid reactive substances production. Moreover, oximes protected tryptophan residues of ApoB-100 in the early stage of LDL oxidation and during the subsequent propagation phase. SIGNIFICANCE: These results indicated for the first time that oximes have a potential antioxidant activity and they could act in the prevention of LDL and serum oxidation. Thus, we speculated that our oximes could act as antiatherogenic compounds besides their well described role as antidote for organophosphate poisoning.

Antioxidant properties of oxime 3-(phenylhydrazono) butan-2-one.

Oximes are a class of compounds normally used to reverse the acetylcholinesterase (AChE) inhibition caused by organophosphates (OPs). Conversely, researches focusing on the possible antioxidant properties of these compounds are lacking in the literature. The aim of this study was to investigate the potential antioxidant and toxic properties of 3-(phenylhydrazono) butan-2-one oxime in mice. In vitro, hydrogen peroxide-induced lipid peroxidation was decreased by low concentrations of the oxime (0.1-1.0 microM); (P < 0.05). Similarly, lipoperoxidation induced by malonate and iron (Fe2+) was significantly decreased by the oxime (0.4-1.0 microM) (P < 0.05). Oxime pre-treatment did not modify the basal peroxidation level nor prevented the induced lipid peroxidation determined ex-vivo. The present results suggest that 3-(phenylhydrazono) butan-2-one oxime could be a good antioxidant compound. The absence of toxicity signs after in vivo administration of 3-(phenylhydrazono) butan-2-one oxime to mice may indicate that it could be a safe drug for further studies.