INTRODUCTION:

NSAIDs are utilized for many medicinal purposes on a global scale. Because of their extensive pharmacological properties, including antipyretic, analgesic, and anti-inflammatory in nature actions, they are regarded as one of the most suitable groups for treating a range of conditions, such as rheumatism and arthritis, as well as for their analgesic properties. Furthermore, aspirin (acetylsalicylic acid), considered a member of this category, has been utilized for over a century^1,2 .

Non-steroidal anti-inflammatory medications (NSAIDs) are widely used pain relievers that specifically inhibit cyclooxygenase (COX) iso-enzymes.³ Prostaglandin H2 is the initial compound formed during the synthesis of several prostacyclin’s, prostaglandins, and thromboxane.^4,5 These compounds play crucial roles in numerous significant pathological and physiological processes^6,7. On the other hand, the COX enzyme is excessively produced in different pathological states such as inflammation⁸.

The structures of both COX-1 and COX-2 enzymes share similarities in their amino acid composition, with approximately 67% of these amino acids being identical. However, there are differences in the remaining amino acids. Specifically, COX-1 has isoleucine (Ile523) as opposed to valine (Val523) in COX-2. This disparity results in the COX-2 binding pocketbeing larger compared to theCOX-1 binding pocket⁹. Prolonged use of medications that primarily inhibit the COX-1 enzyme often results in gastrointestinal side effects, such as ulcers, and can potentially cause harm to the kidneys or liver¹⁰. To address these side effects, researchers have attempted to develop selective NSAIDs like valdecoxib, celecoxib, and rofecoxib¹¹. Nevertheless, the prolonged use of these medicines results in a reduction in the production of prostaglandin I2, leading to cardiovascular side effects¹².

The objective of this study was to create a new set of Quinoline derivatives and assess their effects on COX enzymes. Ultimately, we conducted molecular docking studies to validate the potential binding relationships between the COX enzymes and our drugs. Therefore, it is necessary to develop and uncover new COX inhibitors that are both selective and non-toxic. In this work, we aimed to examine the binding patterns of both known and recently found agents inside the binding domain of COX bacterial, and fungal enzymes. By incorporating past research findings, we were able to achieve our ultimate objective.¹³

METHODOLOGY:

Synthesis:

Procedure: Step-1

The methyl 6-quinoline carboxylate Ⅰ was refluxed with methylated hydrazine hydrate for 6 hours to create quinoline-6-carbothiohydrazide to create quinoline-6-carbothiohydrazide, 20 mmole (3.74g) quinoline-6-carbohydrazide was heated in toluene using 8.09g Lawson’s reagent for 10hours. Quinoline-6-carbothiohydrazide with a 90% purity (3.65g) was obtained by recrystallizing the unprocessed substance in methanol after being cleaned with diethyl ether.¹⁴(Figure 1).

Figure 1: Synthesis of the quinoline thiadiazole derivatives

Step- 2:

Quinoline-6-carbothiohydrazide (0.5mmol) and different aromatic acids (0.5mmol) were combined, and POCl3 (5 ml) was refluxed for 4-6 hours.

The mixture was chilled before being poured over ice. The resultant solid mass that precipitated out was filtered, dried, and crystallised in methanol after being neutralised with NaHCO₃ solution.

Where R:

QT1		3-(5-(Quinolin-6-yl)-1,3,4-thiadiazol-2-yl) benzene-1,2-diol
QT 2		4-(5-(Quinolin-6-yl)-1,3,4-thiadiazol-2-yl)benzene-1,2-diol
QT 3		2-(Pyridin-3-yl)-5-(quinolin-6-yl)-1,3,4-thiadiazole
QT 4		4-(5-(Quinolin-6-yl)-1,3,4-thiadiazol-2-yl)phenol
QT 5		2-(4-Chlorophenyl)-5-(quinolin-6-yl)-1,3,4-thiadiazole

Docking:

The study's target, cyclooxygenase (COX-1), was selected based on the research published in several medicinal chemistry periodicals. A collection of 500 carefully chosen particles were modified to target a specific chemical, namely quinoline thiadiazole derived, that has a strong potential to inhibit the desired Glutamine synthetase.^15,16 The toxicity of the compounds was evaluated using OSIRIS® Property Explorer. The MOLINSPIRATION® tool was used to identify the in-silico drug similarity properties of the produced compounds. 500 molecules were docked towards the target protein using Auto Dock 4®. Five compounds exhibiting favorable interactions and a high docking score (indicating reduced binding energy) were selected. Five compounds, designated as QT-1 to QT-5, were successfully produced. To confirm their purity, the compounds underwent repeated recrystallization. Additionally, their quality was assessed using melting point tests. The synthesized compounds were characterized using IR, NMR, and LC-MS spectroscopic methods.^17,18

Anti-inflammatory assay:

The minimal amount of Dimethyl Formamide (DMF) was used to dissolve the normal medication and the synthesized molecule, which was then diluted with phosphate buffer (0.2 M, PH 7.4). DMF's final concentration in all solutions was under 2.5%. Different drug concentrations in the Test Solution (4ml) were combined with 1ml of a 1mM albumin solution in phosphate buffer, and the mixture was then incubated at 37°C for 15 min. By maintaining the reaction mixture in a water bath at 70°C for 15 minutes, denaturation was induced. The turbidity was measured at 660nm after cooling. The percentage of denaturation inhibition was estimated using a control condition in which no medication was added. As a typical medication, was employed. Using the following formula, the % inhibition of denaturation was determined.^19,20

RESULTS:

Using Autodock®Tools 1.5.6 software, 500 compounds were drew using chemsketch® and docked onto the enzyme known as glutamine synthetase 1. The compounds with favorable interactions and high docking scores were created.^21,22

Table 1: The following compounds were identified as having good docking scores.

Codes	Scoring of docking (kcal/mol^-1)
QT1	-7.75
QT2	-8.52
QT3	-8.56
QT4	-6.52
QT5	-5.87

Figure 1: Thin layer chromatographic profile of synthesized drugs. The retention factor were 0.62, 0.84, 0.78, 0.70, 0.67 for QT1, QT2, QT3, QT4 and QT5 respectively.

Figure 2: melting point of synthesized drugs. The temperature was 239°C, 258°C, 262°C, 260°C, 245°C for QT1, QT2, QT3, QT4 and QT5 respectively.²³

Table 2: Mass Spectra Used to Determine Molecular Weight

Samplename	Actualmass	Calculated mass
QT2	325.39	325.00
QT1	323.38	323.00
QT4	307.38	307.00
QT3	292.37	292.00
QT5	325.87	325.00

Anti inflammatory:

The anti-inflammatory effect of the synthesized compounds was examined utilizing the protein denaturation assay technique. The results of these experiments, which ultimately resulted in their percentage inhibition values, have been presented in tables and graphs²⁴. All the artificial compounds had a slight inhibitory effect.²⁵ When evaluating the effectiveness of the molecules QT1-QT5 at modest doses (100g/ml), they showed potential efficacy in comparison to the STD drug Celecoxib. The inhibition percentages were determined to be 35.86%, 26.70%, 27.16%, 27.60%, 38.54%, and 32.57% for each respective concentration of g/ml. When compared to traditional therapy, Celecoxib, namely component QT5, demonstrates exceptional inhibitory characteristics at all dosage levels²⁶.

CONCLUSION:

New compound called quinoline-thiadiazole Derivative were shown to have the ability to prevent COX-1, enzymes required for the formation of prostaglandins, from doing its job.

The developed compound's docking score ranges from -8.56 to -5.87Kcal/mol. Every compound suppressed inflammation and severe toxicity tests showed that none of the compounds was harmful or unsafe. The compounds that were synthesized produce attractive therapeutic candidates against inflammation with further architectural refinement.

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Received on 25.04.2024 Revised on 16.07.2024

Accepted on 19.09.2024 Published on 10.04.2025

Available online from April 12, 2025

Research J. Pharmacy and Technology. 2025;18(4):1676-1679.

DOI: 10.52711/0974-360X.2025.00240

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