2, 3-Disubstituted Quinazolinones: Study of its Anti-microbial Activity

 

K. Girija¹*, S.Sathiyaraj¹, V. Rajendiran², K. Hemalatha¹

¹Department of Pharmaceutical Chemistry, College of Pharmacy, Mother Theresa Post Graduate and Research Institute of Health Sciences, (A Govt. of Puducherry Institution), Indira Nagar, Gorimedu, Puducherry-605 006, India

^2.Jawaharlal Nehru Technological University, Ananthapur

 

ABSTRACT:

A series of some novel 2, 3-disubstituted quinazolinone derivatives were synthesized by condensing 2-methyl benzoxazine with various amino acids and further reacted with aromatic aldehyde to yield the title compounds. The structures of the synthesized compounds were confirmed by melting point, Thin Layer Chromatography, IR, H¹-NMR, Mass and Elemental Analysis. Lipinski’s rule of five and Druglikeness properties were evaluated using molinspiration software. Docking study of the synthesized compound were carried out by Auto Dock software using Dihydofolate Reductase Inhibitor as a target enzyme. Synthesized derivatives were screened for their anti-bacterial and anti-fungal activities.

 

 

 

INTRODUCTION:

Quinazolinones and their derivatives constitute an important class of heterocyclic compounds. Many of them shows Anti-bacterial^1-3, Anti-fungal^4-5, Anti-cancer^6-7, Anti-inflammatory^8-9, Anti-viral¹⁰, Anti-tuberculosis¹¹, CNS depressant Activity¹², Anti-Parkinsonism activity¹³ etc. Considersing the biological significance of quinazolinone nucleus, it was thought to synthesize a series of some novel 2,3-disubstituted quinazolinone derivatives and optimized with Auto Dock 4.0.1 to investigate the interaction between the target ligand and the amino acid residues of Dihydrofolate reductase and screen them for their anti-bacterial activity.

 

MATERIALS AND METHODS:

An equimolar (0.001 mol) mixture of Anthranilic acid and acetic anhydride were refluxed for 4 hrs. The mixture was cooled to room temperature and poured into crushed ice, filter and then washed with water. The solid thus obtained was recrystallized from ethanol to yield 2-methyl benzoxazine-4-one.

 

An equimolar (0.001 mol) mixture of 2-methyl benzoxazine-4-one were condensed with different aminoacidsand hetero aromatic amino drug (Valciclovir) under reflux for 3 hrs in the presence of glacial acetic acid. The mixture was cooled to room temperature and poured into crushed ice, filter and then washed with water. The solid thus obtained was recrystallized from ethanol to yield 2-methyl-3-substituted quinazolinone derivatives (4a-4j).

 

2-methyl-3-substituted -quinazolinone was condensed with various aromaticaldehydes (4-chloro benzaldehyde, 4-nitro benzaldehyde, 2-hydroxy benzaldehyde, 3-chloro benzaldehyde) in the presence of glacial acetic acid under reflux and the product obtained were recrystallized using absolute alcohol to yield the title compounds (5a-5j).

Melting points were determined in open capillary tubes on a melting point apparatus and are uncorrected. IR spectra were recorded for KBr pellets on a Shimadzu-8400Z- FTIR Spectrophotometer. ¹H-NMR spectra were determined Bruker AMX 400 MHZ with tetramethylsilane as an internal standard. The sample is dissolved in DMSO and the ¹H-NMR value is measured in ppm. Mass spectra were recorded using a Thermo Finnigan LCQ Advantage MAX 6000 ESI Mass spectrometer. Elemental analyses were performed on ThermoFinnigan EA 1112 Elemental Analyser. The synthetic strategy to synthesize the target compounds is depicted in scheme 1. The reaction and the purity of all the compounds are checked by TLC using Chloroform: Methanol (9:1) as an eluent.

 

Preliminary QSAR Study:

The synthesized compounds were subjected to the preliminary QSAR study and drug likeness score using Molinspiration software. The results were shown in table 1 and 2.

 

Table 1: Lipinski’s rule of Five properties:

 

Tabe 2: Druglikeness Properties

 

Figure 1 Binding mode of compounds 5a, 5c, 5g and 5j in the active site of Dihydrofolate reductase

 

Molecular Docking:

Molecular docking was performed for the synthesized compounds using the Auto Dock 4.0 version.  The Structure of Dihydrofolate reductase (PDB ID: 2H2Q) was downloaded from protein data bank (PDB). All the analogs (synthesized compounds) were drawn as 2D structures with Chem Draw Ultra Version 9.0 and are converted into 3D structures using Marvin sketch. The interactions and the docking score are mentioned in table 3 and 4. The binding mode of compounds in the active site of Dihydrrofolate reductase along with the interacting amino acids were shown in Figure 1.

 

Table 3: Interactions of the synthesized compounds with amino acids at the active site of the protein Dihydrofolate Reductase

Table-4 Docking  score of the synthesized  compounds

Sl.No	Compound code	Binding energy (kcal/mol)	Inhibitory constant	Vdw. Desolvation energy
1	5a	-5.14	1.74	-8.71
2	5b	-5.08	2.20	-7.91
3	5c	-8.11	106.33	-8.73
4	5d	-6.10	1.15	-8.97
5	5e	-5.71	306.17	-10.12
6	5f	-6.22	940.40	-9.44
7	5g	-7.01	5.67	-12.72
8	5h	-6.12	32.52	-7.62
9	5i	-5.12	89.59	-7.0
10	5j	-.9.94	6.94	-6.13

Antimicrobial activity:²

The synthezised  compounds (5a-j) were evaluated for their anti-bacterial  activity against Staphylococcus aureus , Bacillus substilis, Salmonella paratyphi and E-coli using paper disc diffusion method and  anti-fungal activity against Candida albicans using Agar well cut method. The results were shown in table 5 and 6.

 

Table 5:Anti-bacterial activity of the synthesized compounds:

 

 

Table 6:  Anti-fungal Activity of the synthesized compounds

 

CONCLUSION:

The synthesized compounds were evaluated for its preliminary physico chemical parameters and drug likeliness score using Molinspiration software. All the compounds obeys Lipinski’s rule of Five. The structure of the synthesized compounds were characterized by FT-IR, 1H-NMR, Mass Spectra and Elemental analysis data. The spectral data of the titled compounds were in correlation with the expected structure. The docking studies of the synthesized compounds were carried out using Auto Dock software. Compounds 5c, 5g and 5j exhibited good hydrogen bond interactions between the atoms of the synthesized compounds and the amino acid residues of DHFR receptor were observed. The synthesized compounds were screened for their anti-bacterial activity by paper disc diffusion method against S.aureus, S. Paratyphi, B.Substilis and E.Coliand Anti-fungal activity against Candida albicans. All compounds exhibited moderate to potent anti-microbial activityat a concentration of 100 mg/ml. compound 5d exhibited good anti-fungal activity compared to the standard Cotrimoxazole.

 

Compound 5a: {2-[(E)-2-(4-chlorophenyl)ethenyl]-4-oxoquinazolin-3 (4H)-yl} acetic acid

Yield 57.5%; TLC R_f= 0.7; mp 68; log P 3.46; IR (KBr): 3405 (C-H, Ar, Stretch), 1617 (C=O), 1540 (C=C, Ar), 1091 (C-N, Stretch), 1383 (C-N), 761 (C-Cl); Anal. Calcd for C₁₈H₁₃ClN₂O₃: C (63.44%) H (3.85%) Cl (10.40%) N (8.22%) O (14.09%)

Compound 5b: 3-(5-aminohexyl)-2-[(E)-2-(4-methyl phenyl) ethenyl]-3,4-dihydro quinazolin-4-one

Yield 71.28%; TLC R_f= 0.8; mp 93; log P 1.194; IR (KBr): 2923 (C-H, Ar, Stretch), 1585 (C=O), 1515 (C=C, Ar), 1225 (C-N, Stretch), 1404 (N-O); EI-MS (M/Z): 250 (M+1);  Anal. Calcd for C₂₂H₂₂N₄O₅: C (62.55%) H (5.25%) N (13.26%) O (18.94%)

 

Compound 5c:2-[(E)-2-(4-chlorophenyl)ethenyl]-3-[4-(methyl sulfanyl) butan-2-yl] quinazolin-4 (3H)-one

Yield 63.55%; TLC R_f= 0.8; mp 66; log P 3.32; IR (KBr): 3125 (C-H, Ar, Stretch), 1669 (C=O), 1587 (C=C, Ar), 1160 (C-N, Stretch), 1403 (C-N), 3473 (C-OH Stretch in acid);¹H-NMR (CDCl₃): δ 7.34-7.9 (m, 5H, Ar-H), 8.1-8.7 (m, 4H, Ar-H), 2.12 (s, 5H, C₂H₅), 0.86 (s, 3H, CH₃), 1.25 (s, 2H, CH=CH), 2.26 (s, 1H, OH);  EI-MS (M/Z): 390 (M+1);  Anal. Calcd for C₂₁H₂₂N₂O₂S: C (68.82%) H (6.05%) N (7.64%) O (8.73%)S(8.75%)

 

Compound 5d: 3-{2-[(E)-2-(4-chlorophenyl)ethenyl]-4-oxoquinazolin-3 (4H)-yl} butanoic acid

Yield 46.75%; TLC R_f= 0.7; mp 51; log P 3.79; IR (KBr): 3444 (C-H, Ar, Stretch), 1558 (C=O), 1416 (C=C, Ar), 1020 (C-N, Stretch), 1383 (C-N), 653 (C-Cl); Anal. Calcd for C₁₇H₁₇ClN₂O₃: C (65.13%) H (4.65%) Cl(9.61%) N (7.60%) O (13.01%)

 

Compound 5e: 2-{2-[(E)-2-(4-chlorophenyl)ethenyl]-4-oxoquinazolin-3 (4H)-yl} butanoic acid

Yield 40.44%; TLC R_f= 0.9; mp 60; log P 4.56; IR (KBr): 3363 (C-H, Ar, Stretch), 1653 (C=O), 1540 (C=C, Ar), 2922 (C-OH, Stretch in acid), 668 (C-Cl); Anal. Calcd for C₂₁H₁₉ClN₂O₃: C (65.88%) H (5.00%) Cl(9.26%) N (7.32%) O (12.54%)

 

Compound 5f: 2-{2-[(E)-2-(4-chlorophenyl)ethenyl]-4-oxoquinazolin-3(4H)-yl} butanedioic acid

Yield 44.06%; TLC R_f= 0.9; mp 58; log P 2.96; IR (KBr): 3364 (C-H, Ar, Stretch), 2922, 2843 (C-OH, Stretch in acid), 1669 (C=O), 1586 (C=C, Ar), 1181 (C-N, Stretch), 753 (C-Cl); Anal. Calcd for C₂₀H₁₅ClN₂O₅: C (60.23%) H (3.79%) Cl(8.89%) N (7.02%) O (20.06%)

 

Compound 5g: 3-[1-1H-1,3- benzodiazol-1-yl) propan-2-yl]-2-[(E)-2-(2-hydroxy phenyl) ethenyl]-3,4-dihydro quinazolin-4-one:

Yield 42.35%; TLC R_f= 0.7; mp 78; log P 4.48; IR (KBr): 3447 (C-H, Ar, Stretch), 1563(C=O), 1540 (C=C, Ar), 1414, 1384 (C-N, Stretch), 2160 (C-OH Stretch in acid), 925 (=CH);¹H-NMR (CDCl₃): δ 7.26 (m, 5H, Ar-H), 1.1 (s, 2H, CH=CH), 1.57 (S, 1H, OH);  EI-MS (M/Z): 456 (M+1);  Anal. Calcd for C₂₆H₂₀N₄O₄: C (69.02%) H (4.46%) N (12.38%) O (14.14%)

 

Compound 5h: 2-{2-[(E)-2-(4-nitrophenyl)ethenyl]-4-oxoquinazolin-3(4H)-yl} pentanedioic acid:

Yield 56.39%; TLC R_f= 0.8; mp 73; log P 2.51; IR (KBr): 3364 (C-H, Ar, Stretch), 2921, 3129(C-OH, Stretch in acid), 1563 (C=O), 1540 (C=C, Ar), 1161 (C-N, Stretch), 1516 (N-O Stretch in NO₂); Anal. Calcd for C₂₁H₁₇ClN₃O₇: C (59.57%) H (4.05%) N (9.92%) O (26.45%)

 

Compound 5i: 2-{2-[(E)-2-(3-chlorophenyl)ethenyl]-4-oxoquinazolin-3(4H)-yl} -3-phenyl propanoic acid

Yield 46.74%; TLC R_f= 0.9; mp 70; log P 5.22; IR (KBr): 3417 (C-H, Ar, Stretch), 2921(C-OH, Stretch in acid), 1608 (C=O), 1556 (C=C, Ar), 1091 (C-N, Stretch), 764 (C-Cl); Anal. Calcd for C₂₅H₁₉ClN₂O₃: C (69.69%) H (8.23%) Cl(4.44%) N (6.50%) O (11.14%)

 

Compound 5j: 2-{2-[(E)-2-(4-chlorophenyl)ethenyl]-4-oxo-3,4-dihydroquinazolin-3(4H)-yl} -6-oxo-6,9-dihydro-1H-purin-9-yl) methoxy] ethyl-2-amino-3-methyl butanoate:

Yield 35.64%; TLC R_f= 0.8; mp 54; log P 3.63; IR (KBr): 3443 (C-H, Ar, Stretch), 1557 (C=O), 1416 (C-N, Stretch), 650(C-Cl); Anal. Calcd for C₂₉H₂₈ClN₇O₅: C (60.47%) H (5.25%) Cl(6.15%) N (17.02%) O (11.11%)

 

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