Original Article
Int. J. Chem. Sci, Volume: 16( 3) DOI: 10.21767/0972-768X.1000278

Design, Synthesis, Characterisation and Pharmacological Evaluation of Some Novel Substituted Pyrimidine 2-one Derivatives

*Correspondence:
Gejalakshmi S , Faculty of pharmacy, Department of Pharmaceutical Chemistry, Dr. M.G.R, Educational and Research Institute, Vellapanchavadi, chennai-77, Tamil Nadu, India, Tel: 9790084747, E-mail: [email protected]

Received: June 27, 2018; Accepted: August 24, 2018; Published: August 29, 2018

Citation: Gejalakshmi S, Harikrishnan N. Design, Synthesis, Characterisation and Pharmacological Evaluation of Some Novel Substituted Pyrimidine 2-one Derivatives. Int J Chem Sci. 2018;16(3):278

Abstract

2,3-dihydropyrimidin-2(1H)-one derivatives were known to undergo cyclo-condensation of benzaldehyde, urea and ethyl acetoacetate and evaluate their antioxidant and in vitro anti-inflammatory activity. Dihydropyrimidinones are mainly synthesized by Biginelli reaction, which involves cyclo condensation of benzaldehyde, urea and ethyl acetoacetate. The prepared compounds were characterized by noting their melting point, thin layer chromatography ultraviolet spectroscopy, infrared spectroscopy, nuclear magnetic resonance and Mass spectroscopy and were scrutinized for its in vitro anti-inflammatory activity and antioxidant activity by in vitro cell culture studies. The melting point, thin layer chromatography and ultraviolet spectroscopy of the synthesized compounds were found to be pure and identified chemically. The molecular structure and molecular mass of compounds were confirmed by Infrared, nuclear magnetic resonance and Mass spectroscopy. The IC50 value of compound 1 and compound 2 by hydrogen peroxide method was found to be 30.25 μg/ml and 26.06 μg/ml respectively. The IC50 value of compound 1 and compound 2 by DPPH assay method was found to be 27.872 μg/ml and 25.467 μg/ml respectively. Synthesized compounds also show anti-inflammatory activity. The result obtained in this research work is clearly indicating that the synthesized molecules possess both antioxidant activity and anti-inflammatory activity.

Keywords

Anti-inflammatory activity; Biginelli reaction; Dihydropyrimidinones; Docking; DPPH

Introduction

Dihydropyrimidinone is a heterocyclic moiety having two N-atoms at positions 1 and 3. They are pyrimidine spinoffs having a ketone group. Dihydropyrimidinones are a series of highly valuable small molecules possessing versatile pharmaceutical properties [1]. Dihydropyrimidine core unit containing alkaloids have been isolated from marine sources, like batzelladine which also having different pharmacological properties. These pyrimidinone derivatives are reported to have diverse pharmacological activities such as anti-inflammatory [2], anticonvulsant, analgesic, sedative, anti-depressant, antipyretic, antioxidant [3], antitumor activity and antihypertensive activities [4,5]. The research was to design and synthesize 2,3-dihydropyrimidin-2(1H)-one derivatives and evaluate their antioxidant and in vitro anti-inflammatory activity (SCHEME 1).

international-journal-chemical-sciences-pyrimidone-derivatives

SCHEME 1. Synthesis of substituted pyrimidone derivatives.

Experimental Section

Synthesis of 2,3, -dihydropyrimidin-2(1H)-one derivatives

Two 2, 3 dihydropyrimidin-2-(1H)-one derivatives were selected. The docking analysis reveals the good activity against the selected anti-inflammatory targets [6-10]. The main mechanism for these ligand syntheses was based on aldol condensation. Ethyl acetoacetate reacted with benzaldehyde in the presence of acid catalyst to form an intermediate and the corresponding intermediate was reacted with urea to form 3, 4-dihydropyrimidin-2-(1H)-one.

Equation

in vitro anti-inflammatory activity

Determination of in vitro anti-inflammatory effect on cultured Raw 264.7 cell lines by COX-2 inhibitory assay

The in vitro anti-inflammatory activity of 3,4-dihydropyrimidine-2-(1H)-one analogues was evaluated using LPS stimulated Raw 264.7 macrophage cell line [11,12]. Different concentrations (25,50,100 μg/mL) of synthesized compounds and control were tested for in vitro anti-inflammatory study and inhibition of COX-2 level was determined. Percentage inhibition of COX-2 level by synthesized molecule is shown in table.

in vitro antioxidant activity

3,4–dihydropyrimidin-2-(1H)-one analogues were analyzed by DPPH and hydrogen peroxide free radical scavenging activity (TABLES 1-8). Standard drug used here is ascorbic acid [13].

Compound code Docking score (kcal/mol)
CS1 -10.3878
CS2 -9.8562
Diclofenac -10.2105

TABLE 1. Docking Score for the synthesized compounds using Argus lab software.

Compound code Docking score (kcal/mol)
CS1 -7.478
CS2 -6.616
Diclofenac -7.375

TABLE 2. Docking Score for the synthesized compounds using autodock software.

Compound code Molecular formula MW (g/mol) No. of HBA No. of HBD C Log P No of rotable bonds TPSA (Å2)
CS1 C17H22N2O3 302.37 5 2 3.88 5 67.43
CS2 C14H15N3O5 305.29 8 2 2.31 5 113.2

TABLE 3. Structural elucidation of the compounds.

Compound code Molecular formula MW (g/mol) Melting point (°C) Percentage yield
CS1 C17H22N2O3 302.37 210-215 78.41%
CS2 C14H15N3O5 305.29 210-212 70.6%

TABLE 4. Physical characterization of the synthesized compounds.

Properties CS1 CS2
Nature Powder form Powder form
Odour Pleasant odour No odour
Colour Yellow Pale white
State Solid state Solid state

TABLE 5. Physical property of synthesized compounds.

Compound code Soluble Partially soluble Insoluble
CS1 DMSO, DMF Chloroform, Hexane, Methanol Water
CS2 DMSO, DMF Chloroform, Hexane Water

TABLE 6. Solubility nature of the synthesized compounds.

Compound code Structure IUPAC name Solvent system Rf Value
CS1   Ethyl 4-(4-isopropylphenyl)-6-methyl-2-oxo-3,4-dihydro-1H-pyrimidine-5-carboxylate Hexane: Ethyl acetate (7:3) 0.43
CS2   Ethyl 4-[3-nitrophenyl]-6-methyl-2-oxo-3,4-dihydro-1H-pyrimidine-5-carboxylate Hexane: Ethyl
Acetate (7:3)
0.57

TABLE 7. IUPAC name of the synthesized compounds.

Compound code Chemical structure IR (cm-1)
CS1   2960.73 cm-1 (alkane C-H str)
3116.97 cm-1 (aromatic C-H str)
3331.07 cm-1 (N-H str)
1691.57 cm-1 (C=O str)
1438.90 cm-1 (aromatic C=C str)
CS2   2964.59 cm-1 (alkane CH str)
3315.54 cm-1 (NH str)
3103.46 cm-1 (aromatic CH str)
1691.57 cm-1 (C=O str)
1521.84 cm-1 (N=O str)
1220.94 cm-1 (CN str)

TABLE 8. IR spectral studies of the synthesized compounds.

Hydrogen peroxide free radical scavenging activity

Percentage inhibition of the synthesized compound was found out by hydrogen peroxide free radical scavenging activity technique and the results were shown in the TABLE 9.

  Compound code Percentage inhibition ± SD
10 µg/mL 20 µg/mL 30 µg/mL 40 µg/mL 50 µg/mL
CS1 22.5 ± 0.025 33.8 ± 0.052 53.2 ± 0.045 65.2 ± 0.033 73.6 ± 0.009
CS2 28.5 ± 0.038 42.5 ± 0.051 57.1 ± 0.021 67.8 ± 0.011 78.9 ± 0.023
Ascorbic acid 32.6 ± 0.014 48.4 ± 0.023 59.5 ± 0.012 74.2 ± 0.007 81.5 ± 0.006

TABLE 9. Antioxidant activity with standard deviation.

Graphical representation of the inhibitory activity of the synthesized derivatives

This graph was schemed against concentration on X-axis and percentage inhibition on Y-axis [14-16]. On increasing the concentration of the sample percentage inhibition also increases; as a result, free radical scavenging activity increases. IC50 value of the derivatives was resoluted using Microsoft Excel.

Comparing the antioxidant activity of standard drug and synthesized compound by hydrogen peroxide free radical assay method

It was perceived that the maximum hydrogen peroxide scavenging activity was showed by CS2 (IC50=26.06 μg/mL). CS2 exhibited more scavenging property compared to CS1.

2, 2-diphenyl-1-picryl hydrazyl free radical assay

In this method the presence of an antioxidant species the DPPH undergoes reduction. The synthesized analogues have hydrogen donating power, which diminish the color of DPPH [17-20]. The results obtained from the DPPH assay of synthesized compound showing significant antioxidant activity when compared to reference standard (TABLE 10).

  Compound code Percentage inhibition ± SD
10 µg/mL 20 µg/mL 30 µg/mL 40 µg/mL 50 µg/mL
CS1 20.906 ± 0.124 40.887 ± 0.007 49.476 ± 0.175 68.286 ± 0.03382 88.694 ± 0.003
CS2 15.973 ± 0.005 40.849 ± 0.005 60.296 ± 0.0004 67 ± 0.004 96.475 ± 0.0008
Ascorbic acid 18.322 ± 0.004 38.674 ± 0.012 56.743 ± 0.003 65.461 ± 0.004 91.592 ± 0.016

TABLE 10. Antioxidant activity without standard deviation.

DPPH free radical assay

The IC50 value of synthesized compound by DPPH assay method is shown in the graph [21-24]. It shows that IC50 value of the synthesized compound CS1 and CS2 was found to be 27.872 μg/mL and 25.467 μg/mL respectively. IC50 value of standard ascorbic acid was found to be 27.636 μg/mL. The experimental results uphold that the synthesized derivatives have the ability to prevent the oxidation [25,26].

Graphical depiction of the inhibitory activity of the synthesized derivatives

This graph was plotted against concentration Vs percentage inhibition [27]. When the concentration increases, percentage inhibition also increases. It indicates that the synthesized compounds possess free radical activity. IC50 value of the compound was determined using Microsoft Excel (TABLE 11).

  Compound code Percentage inhibition
25 µg/mL 50 µg/mL 100 µg/mL  
CS1 26.51473 ± 0.1322 30.23902 ± 0.1255 44.52474 ± 0.0998  
CS2 32.35131 ± 0.1217 35.13063 ± 0.1167 45.85881 ± 0.0974  
Diclofenac 78.4924 ± 0.0973 88.48619 ± 0.0521 93.21547 ± 0.0307  

TABLE 11. Anti-inflammatory activity.

In silico molecular modelling

A series of Dihydropyrimidinone analogues were chosen and performed insilico modelling docking studies [28,29], Lipinski’s rule of five analysis. Softwares like ChemSketch, Molinspiration, Arguslab and Schrodinger are used for molecular modelling. Studies were performed by using 5C29 COX-2 selective receptors. The higher docking score derivatives are selected for further synthesis and study. The docking score of the ligands were compared with the reference standard shown in TABLE 11.

Results, Discussion and Conclusion

2,3-Dihydropyrimidin-2-(1H)-ones are therapeutically beneficial scaffolds possessing remarkable biological activities. The current research work was based on the anti-inflammatory and antioxidant activities of 3, 4-dihydropyrimidin-2-(1H)-one analogues. The selected analogues were subjected to in silico molecular modelling using selective COX-2 anti-inflammatory (5c29) receptor. For further clarification of these compounds, they were subjected to drug likeness analysis using Lipinski Rule of Five. The derivatives were synthesized by Biginelli reaction, which involves cyclo-condensation of benzaldehyde, urea and ethyl acetoacetate. The yield of the synthesized compounds was found to be substantial. The synthesized new series of compounds were authenticated by melting point, TLC and spectral analysis. IR spectra of the compound was analyzed and thus the synthesized compounds were found to be pure and chemically recognized.

The molecular structure and molecular mass of the derivatives were confirmed by NMR and Mass spectroscopy respectively. These analogues were screened for in vitro antioxidant (1,1-diphenyl 2-picryl hydrazyl and H2O2 free radical scavenging) activity and anti-inflammatory activity by Raw 264.7 cell lines. From the study, it was discerned that CS2 showed reasonably better antioxidant and anti-inflammatory activity than CS1. In 3, 4-dihydropyrimidin-2-(1H)-one derivatives, the derivative with electron withdrawing nitro group in the third position showed better antioxidant and anti-inflammatory properties than isopropyl group substituted derivative. The results of this research unveiled that these synthesized analogues be likely to have moderate activity against COX-2 mediated diseases, thereby it may decrease pain and inflammation because of its antioxidant and anti-inflammatory activity.

References