Synthesis and antimicrobial evaluation of some novel 1,5 benzodiazepine derivatives derived from pyrrolyl chalcones

 

Pankaj Kumar1, Abhishek Kumar1*, Jean Sandra Pinto1, Sachin A. Kumbar1, Nanditha Bhat1, Prashant Nayak2

1Department of Pharmaceutical Chemistry, NGSM Institute of Pharmaceutical Sciences,

NITTE (Deemed to be University), Paneer, Deralakatte-575018, Mangaluru, Karnataka, India.

2Department of Pharmaceutics, NGSM Institute of Pharmaceutical Sciences,

NITTE (Deemed to be University), Paneer, Deralakatte-575018, Mangaluru, Karnataka, India.

*Corresponding Author E-mail: abhi12bunty@gmail.com

 

ABSTRACT:

The α,β unsaturated ketone 3-(2,4-dimethyl-1H-pyrrol-3-yl)-1-phenylprop-2-en-1-onederivatives were treated with benzene-1,2-diamine to obtain 2-(2,4-dimethyl-1H-pyrrol-3-yl)-4-phenyl-2,3-dihydro-1H-benzo[b][1,4]diazepine derivatives. These synthesized compound were characterized by IR, 1H NMR, and mass spectroscopy. These synthesized molecules were evaluated for invitro antimicrobial activity. All The synthesized compounds, showed potent anti-microbial activity as compare to reference drug. In these study the synthesized were docked with Type IIA topoisomerases 2XCT using glide dock program and binding affinity were predicted for the synthesized compounds. The compound AP8 and AP9 have shown more active as per binding energy.

 

KEYWORDS: Benzodiazepines, Antimicrobial, Docking, Topoisomerases, o-Phenylenediamine.

 

 


INTRODUCTION:

Benzodiazepines have been attracted as an essential class of heterocyclic compound in the field of clinical research. Different substituted benzodiazepine comprise an imperative class of therapeutic compound for example antimicrobial1, anticonvulsant2, pain relieving3, anticancer4, and neuroleptic. Aside from this significance, benzodiazepines are important intermediates for the synthesis of combination of intertwined ring for example, triazolo, thiazolo, imidazo, oxodiazolo, oxazino, furano and pyrimido benzodiazepines. These substituted benzodiazepines are synthesized from chalcones as intermediate known for their antimicrobial5, antitubercular6, anticancer7, antimalarial8, antioxidant, anti-inflammatory9,10 and calming activities. The regular strategy for the synthesis of the benzodiazepines moiety is the reaction of chalcones with o-phenylenediamine. Apart from the regular method of synthesis some methodologies involve the use of inorganic support, for example, silica gel, clay, alumina, TFA or few drops of piperidine under reflux condition or microwave irradiation. A number of these processes suffer from some constraints; requiring harsh conditions. Prompted by these reported works it was accounted for the synthesis of some novel substituted benzodiazepine from different substituted chalcones to improve the benzodiazepines for its antimicrobial activity.

 

MATERIALS AND METHODS:

Completion of the reaction and homogeneity of the compounds was checked by thin layer chromatography. Melting points were determined by open capillary and are uncorrected. IR spectra were recorded by open capillary and are uncorrected. IR spectra were recorded on an FTIR spectrophotometer.1 H NMR spectra were recorded on a Bruker spectrometer (Germany, 400 MHz) in CDCl3 using TMS as an internal standard. Mass spectra were recorded by using Shimadzu LCMS 2010 (USA). Purity of the compounds was checked on silica gel coated plates by using Cyclohexane: Methanol(8:2) as the solvent and observed in UV light. Elemental analysis was carried out using Vario Elemental Model CHN analyzer instrument.

 

General Procedure:

Step I: Pyrrolyl Chalcones:

A solution of 1-(2,4-dimethyl-1H-pyrrol-3-yl) ethanone (0.01 mol) and substituted benzaldehyde (0.01 mol) in 20 ml of absolute alcohol was stirred for 18h in presence of 3-5 ml of 20% NaOH. The resulting mixture was poured into the crushed ice and acidified with HCl. The product was filtered, washed with water, and dried11.

 

Step II:2-(2,4-dimethyl-1H-pyrrol-3-yl)-4-phenyl-2,3-dihydro-1H-benzo[b][1,4]diazepine (AP1-AP9):

Chalcones (0.01 mol) and hydroxylamine (0.01 mol) were dissolved in 30 ml methanol in presence of 20% NaOH and the mixture was refluxed for 10 h. The reaction mixture was poured into crushed ice and the product was filtered, washed with water and dried. Product was recrystallized from ethanol. Rf value was determined using Cyclohexane: Methanol (8:2) as mobile phase. The Physical data of Benzodiazepine derivatives (AP1-AP9) shown in Table 1

 

SCHEME:

 

Spectral Data:

2-(2,4-dimethyl-1H-pyrrol-3-yl)-4-(4-nitrophenyl)-2,3-dihydro-1H-benzo[b][1,4]diazepine (AP1):

This compound was obtained as brown crystals (ethanol); mp 128-130oC; Yield 74%

IR (vmax., KBr): 1640 cm-1 (Ar C=C str), 3050 cm-1 (Ar C-H str), 3300 cm-1 (N-H str of benzodiazepine) ;

1H NMR (DMSO-d6, 300MHz, δ):8.1-6.9 (m, 8H, Ar-H), 2.1, 3.4, 4.1 (d, 3H of benzodiazepine), 5.7 (s, 1H, NHpyrrol);

MS: m/z 362 M+;

Analysis calculated for C21H20N4O2: C, 69.98; H, 5.59; N, 15.55 Found: C, 69.72; H, 5.61; N, 15.55;

 

2-(2,4-dimethyl-1H-pyrrol-3-yl)-4-(4-fluorophenyl)-2,3-dihydro-1H-benzo[b][1,4]diazepine (AP3):

This compound was obtained as brown crystals (ethanol); mp 136-138oC; Yield 57%

IR (vmax., KBr): 1648 cm-1 (Ar C=C str), 3060 cm-1 (Ar C-H str), 3310 cm-1 (N-H str of benzodiazepine), 1585 (C=N str of benzodiazepine), 1120(C-F str)748 cm-1 (Ar C-H bend), 1347 (N=O str of R-NO2);

1H NMR (DMSO-d6, 300MHz,δ):8.1-6.9 (m, 8H, Ar-H), 2.1, 3.4, 4.1 (d, 3H of benzodiazepine), 5.7 (s, 1H, NHpyrrol);

MS: m/z 334 M+;

Analysis calculated for C21H20FN3: C, 75.65; H, 6.05;N, 12.60 Found: C, 75.62; H, 6.01;N, 12.64.

 

2-(2,4-dimethyl-1H-pyrrol-3-yl)-4-(2-methoxyphenyl)-2,3-dihydro-1H-benzo[b][1,4] diazepine(AP7):

This compound was obtained as dark red crystals (ethanol); mp 123-125-oC; Yield 71%

IR (vmax., KBr): 1660 cm-1 (Ar C=C str), 3030 cm-1 (Ar C-H str), 3340 cm-1 (N-H str of benzodiazepine), 1530 (C=N str of benzodiazepine), 760 cm-1 (Ar C-H bend)

1H NMR (DMSO-d6, 300MHz, δ):8.1-6.9 (m, 8H, Ar-H), 2.1, 3.2, 4.1 (d, 3H of benzodiazepine), 5.4 (s, 1H, NHpyrrol):2.4 (s, 3H of OCH3);

MS: m/z 346 M+; Analysis calculated for C22H23N3O: C, 76.49; H, 6.71; N, 12.16; Found: C, 76.11; H, 6.51; N, 12.16;

 

Molecular docking study:

A molecular docking study was performed to know the interactions between ligand (synthesized compounds) and receptors. All computational analysis was carried out on Schrodinger 2018-3 suite device Maestro 11.7.012, (ligprep, glide XP docking, grid generation). This software package is programmed on DELL Inc.27 workstation machine running on Intel Core i7-7700 CPU@ 3.60 GHz x8, the processor with 8GB RAM and 1000 GB hard disk with Linux X6_64 as the operating system. For docking calculation, the protein Type IIA topoisomerases (PDB code:2XCT) was downloaded from the protein data bank and refined using protein preparation wizard. Docking score were calculated using maestro (Schrodinger) software. The binding affinity was assessed in terms of binding free energies (S-score, kcal/mol). All synthesized compounds were docked in the groove of the binding site present in Type IIA topoisomerases. The affinity of the compounds with receptors is listed in Table 2 in terms of the S-score. The compounds giving the best docking based on binding free energy were AP8 and AP9. The interaction pattern of AP5 AP8 and AP9 in the form of 2D and 3D form is shown in Figure 1, 2 and 3

 

Antimicrobial Activity:

Microbial growth inhibitory properties of test substances were determined by the cup plate method. The drugs were initially dissolved in H2O2/DMSO and tested at concentrations of 100μg/ml against all the microorganisms. Sterile nutrient agar plates were prepared and 0.1 ml of the inoculum from the standardized culture of the test organism was spread uniformly. Wells were prepared by using a sterile borer of diameter 10 mm and 100μl of the test substance, standard antibiotic and solvent control were added in each well separately. Standard antibiotic, ciprofloxacin was tested against gram-negative, gram-positive bacteria respectively. The plates were placed at 4C for 1 h to allow the diffusion of test solution into the medium and plates were incubated at a temperature optimal for the test organism and for a period of time sufficient for the growth of at least 10 to 15 generations (usually 24 h at 37C). The zone of inhibitions of microbial growth around the well was measured in mm.

 

RESULTS AND DISCUSSION:

Table1: Physical data of Benzodiazepine derivatives (AP1-AP9)

Comp.

code

R

Mol.

formula

Mol. wt

M.poC

Rf Value

Yield

(%)

AP1

4-NO2

C21H20N4O2

361

128-130

0.54

74

AP2

4-OCH3

C22H23N3O

346

118-120

0.62

63

AP3

4-F

C21H20FN3

334

136-138

0.65

57

AP4

4-Cl

C21H20ClN3

350

144-146

0.70

66

AP5

4-(CH3)2N

C23H26N4

359

129-131

0.60

67

AP6

2-NO2

C21H20N4O2

361

123-125

0.58

72

AP7

2-OCH3

C22H23N3O

346

123-125

0.68

71

AP8

2-F

C21H20FN3

334

130-132

0.59

69

AP9

2-Cl

C21H20ClN3

350

138-140

0.61

64

 

Table2: Docking score of Benzodiazepine derivatives (AP1-AP9)

Ligand Code

AP1

AP2

AP3

AP4

AP5

STD

G Score

-2.12

-4.79

-4.54

4.41

-3.87

-7.75

 

Ligand Code

AP6

AP7

AP8

AP9

STD

G Score

-4.45

-3.25

-5.25

-5.10

-7.75

 

Table3: Antimicrobial activity of Benzodiazepine derivatives (AP1-AP9)

Compd

Diameter of zone of inhibition (mm)

S.aureus

B.subtilis

E.coli

P.aureginosa

AP1

11

13

14

12

AP2

15

17

13

11

AP3

18

17

16

16

AP4

12

09

10

09

AP5

11

10

09

12

AP6

13

14

16

11

AP7

07

09

09

11

AP8

20

19

17

17

AP9

19

20

18

15

Ciprofloxacin

26

26

22

23

Control

-

-

-

-

 


 

Figure1. Ligand interaction and the binding mode 2D and 3D of compound A P8 with 2XCTreceptor

 

Figure2. Ligand interaction and the binding mode 2D and 3D of compound AP9 with 2XCT receptor

 

Figure3 Ligand interaction and the binding mode of 2D and 3D compound A P5 with 2XCTreceptor

 


Antimicrobial activity:

Among the screened compounds, AP3, AP8 and AP9 have shown good antibacterial activity against gram +ve and gram -ve bacteria compared to the standard drug. The zone of inhibition for synthesized compound AP1-AP9 is in Table 3.

 

CONCLUSION:

All the synthesized compounds AP1-AP9 docking studies and antibacterial activity against gram +ve and gram -ve bacteria were performed. The molecular docking within the groove of the binding site present in Type IIA topoisomerases (PDB Code 2XCT) has exhibited good ligand interaction and binding affinity. The compounds AP8 and AP9 showed the best docking score of -5.10 and -5.25. For each compound, the Diameter of the zone of inhibition (mm) was calculated and presented. All the synthesized Benzodiazepine derivatives have shown different zone of inhibition values. Compounds AP3, AP8, and AP9 respectively exhibited maximum activity.

 

ACKNOWLEDGEMENTS:

The authors are thankful to Nitte University for providing all the research facilities and financial assistance and Mangalore University for elemental analysis. The authors are also thankful to
VIT University, Vellore for NMR and Mass spectroscopic analysis.

 

REFERENCES:

1.      Ilango SS, Remya PU, Ponnuswamy S. Synthesis, and antimicrobial activity of novel 1,5-benzodiazepines. Indian. J. Chem., 2013; 52B: 136-140.

2.      De Sarro G, Gitto R, Rizzo M., Zappia M., De Sarro A. 1,4-Benzodiazepine derivatives as anticonvulsant agents in DBA/2 mice. Gen. Pharmacol.1996; 27(6):935-941. DOI: 10.1016/0306-3623(95)02147-7

3.      Najafi N, Pirali M, Dowlatabadi R, Bagheri M, Rastkari N, Abdollahi M. Synthesis and analgesic and anti-inflammatory properties of new benzodiazepine derivatives. Pharmaceutical Chemistry Journal. 2005; 39(12):641-3. DOI :10.1007/s11094-006-0036-4

4.      Tardibono LP, Miller MJ. Synthesis and anticancer activity of new hydroxamic acid containing 1,4 benzodiazepines. Org. Lett., 2009; 11(7):1575-1578. DOI :10.1021/ol900210h

5.      Burmaoglu S, Algul O, Gobek A, Aktas AD, Ulger M. Aslan, G. Design of potent fluoro-substituted chalcones as antimicrobial agents. J. Enzyme. Inhib. Med. Chem., 2107; 32(1):490-495. DOI: 10.1080/14756366.2016.1265517

6.      Hans RH, Guantai EM., Lategan C, Smith PJ, Synthesis, antimalarial and antitubercular activity of acetylenic chalcones. Bioorg. Medicinal. Chem Lett .2010; 20(3):942-944. DOI: 10.1016/j.bmcl.2009.12.062

7.      Syam S, Abdelwahab SI, Al-Mamary MA, Mohan S. Synthesis of chalcones with anticancer activities. Molecules. 2012;17(6):6179-95. DOI: 10.3390/molecules17066179

8.      Tavadyan LA, Manukyan ZH, Harutyunyan LH, Musayelyan MV, Sahakyan AD, Tonikyan HG. Antioxidant properties of selenophene, thiophene and their aminocarbonitrile derivatives. Antioxidants. 2017;6(2):22. DOI: 10.3390/antiox6020022

9.      Nowakowsk Z. A review of anti-infective and anti-inflammatory chalcones. Eur. J. Med. Chem. 2007, 42(2):125-137. DOI: 10.1016/j.ejmech.2006.09.019

10.   Kumar P, Fernandes J, Kumar A. Synthesis and Antimicrobial Evaluation of Substituted Oxazolidinones Moieties. Res. J. Pharm. Technol. 2017;10(1):98-100. DOI: 10.5958/0974-360X.2017.00023.3

11.   Kumar P, Kumar A, Nayak P. Synthesis and Antimicrobial evaluation of Some novel Mercapto Pyrimidine via Pyrrole chalcone. Res. J. Pharm. Technol. 2018;11(7):2765-7. DOI: 10.5958/0974-360X.2018.00511.5

 

 

 

Received on 07.05.2019 Modified on 25.09.2020

Accepted on 21.07.2021 RJPT All right reserved

Research J. Pharm.and Tech 2022; 15(4):1811-1814.

DOI: 10.52711/0974-360X.2022.00304