Investigation of inhibitory effect of novel synthetic 1,3,4-thiadiazole derivatives on acetylcholinesterase enzyme.
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Mahsa Taghavi,1 Safa Lotfi,2,* Elham Rezvannejad,3 Mohammad Reza Hajizade,4
1. Department of Biotechnology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran.
2. Department of Biotechnology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran.
3. Department of Biotechnology, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, Iran.
4. Department of Clinical Biochemistry, Faculty of Medicine, Rafsanjan University of Medical Sciences, Rafsanjan, Iran.
- Introduction: Alzheimer’s disease (AD) that is the most common cause of dementia is a progressive neurodegenerative disease which ultimately leads to death. According to the cholinergic hypothesis of AD pathogenesis, the clinical features of AD are attributed to the decrease of acetylcholine, a neurotransmitter participating in memory and learning process, in the brain hippocampus and cortex [3,4]. Therefore, the administration of acetylcholinesterase enzyme (AChE) inhibitors is very common for the symptomatic treatment of mild to moderately severe forms of AD. AChE inhibitors are also utilized to manage the other forms of dementia and CNS disorders such as Parkinson’s disease (PD), dementia with Lewy bodies, Down’s syndrome, and Korsakoff disease. Nowadays, worldwide research is being conducted to design and develop novel potent AD drugs with higher therapeutic efficacy and less side effects.
Thiadiazole is a common and important heterocyclic compound containing two carbon atoms, two nitrogen atoms and a sulfur atom. There are several thiadiazole isomers, of which 1, 3,4-thiadiazole has been studied the most. 1, 3,4-thiadiazole derivatives exhibit a wide range of biological activities such as antimicrobial, antifungal, antioxidant, anti-inflammatory and anticancer.
In this paper, the effect of eight novel synthetic compounds containing 1,3,4-thiadiazole ring on the inhibition of AChE activity has been investigated.
- Methods: Ellman method was used to evaluate the ability of the novel synthetic thiadiazole derivatives to inhibit AChE (from electric eel) and the results were reported as the half maximal inhibitory concentration (IC50) of the derivatives.
To determine the IC50 of the thiadiazole compounds, the enzyme activity were determined in the absence and presence of at least seven different concentrations of the derivatives. Each concentration was analyzed in triplicate and neostigmine was used as the reference compound. All the enzyme assays were performed in 96-well plate with final volume of 200 µl.
The assay mixture contained 0.1 M potassium phosphate buffer (pH 8.0) and the enzyme (AChE) and Ellman’ reagent (DTNB) with the final concentrations of 0.1 unit/ml and 0.5 mM, respectively. The compounds were incubated with the assay mixture at 25 oC for 10 minutes. The substrate (acetylthiocholine iodide) was then added to the assay with final concentration of 1 mM and the absorbance was read after 10 minutes at 405 nm by a microplate reader. A sample containing all the assay components except the enzyme was applied as blank. Finally, the percentage of enzyme inhibition at each concentration of the compounds was calculated and IC50 values were determined using the dose response curves plotting the inhibition percentage versus the logarithm of inhibitors concentration. The results were reported as the mean ± standard deviation (SD).
- Results: All the eight thiadiazole derivatives studied were capable of inhibiting AChE. The IC50 values of the compounds were variable between 0.016 ± 0.0015 and 0.084 ± 0.003 µM. The IC50 value of the most active compound, 4d, was almost equal to that of the reference compound (0.014 ± 0.0015).
- Conclusion: In this study, the anticholinesterase activity of eight novel synthetized compounds containing 1,3,4-thiadiazole ring was studied. The results showed that the compound 4d is the powerful inhibitor of AChE and has a great potential for further studies.
- Keywords: Alzheimer’s disease (AD), Acetylcholinesterase enzyme (AChE),1,3,4-Thiadiazole, Ellman method.
