P: ISSN No. 2231-0045 RNI No.  UPBIL/2012/55438 VOL.- XI , ISSUE- IV May  - 2023
E: ISSN No. 2349-9435 Periodic Research
A Convenient Synthesis of Substituted Dihydropyridine Derivative and its Bioevaluation
Paper Id :  17625   Submission Date :  21/04/2023   Acceptance Date :  30/04/2023   Publication Date :  05/05/2023
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Neetu Tripathi
Assistant Professor
Chemistry Department
M.K.P. P.G. College
Dehradun,Uttarakhand, India
Abstract Pyridine is a nitrogen containing six membered heterocyclic compounds which is found in many important organic compounds. Pyridine is also used as solvents to dissolve many substances. Nitrogen containing heterocyclic compounds are very common in some existing drugs like Isoniazid, Pyrazinamide etc hence, play important role in the treatment many infectious diseases. 1,4 dihydropyridine is reduced form of pyridine and very actively involved in therapeutic agents. It is a multifunctional compounds and capable of producing different substituted derivatives. 1,4 Dihydropyridine derivative was synthesized by an efficient method of three component reaction between an aldehyde, ammonium acetate and beta di keto compound to give substituted 1,4-dihydropyridine compound and evaluated for antimicrobial activity against bacteria and fungi.
Keywords Dihydropyridine, Ethylene Glycol, Benzaldehyde, Microorganisms, Antimicrobial.
Introduction
Pyridine is an aromatic heterocyclic compound used as organic solvents. It has very unpleasant odour and due to presence of nitrogen , it is basic in nature. It is used as a raw material in many chemical industries. It is a widely used as antiseptic, in pharmaceutics for making ant freezing compounds, and as a disinfectant. Further its use in dye and paint industries is very common. Pyridines are also used as ligands in preparation of coordination complexes. Agricultural and food industries are using pyridine derivative as insecticidal agents [1-2]. Reduction at the 1 and 4 position of the Pyridine give more active compound i.e. 1-4 dihydropyridine. These are also known to act as neuroprotectants anti-platelet aggregators. They are also very important in the treatment of Alzheimer,s diseases anti-schemic agents [3-6]. It is interesting to note that an enzyme Nicotinamide Adenine Dinucleotide (NADH) is also related to 1, 4 Dihydro-pyridine nucleus. This co-enzyme play very important role in biological system. Several new derivatives of 1, 4-dihydropyridine have been synthesized and evaluated for their biological activities. [7]. Microbiologists work on antibiotics which are the compounds that either kills bacteria or prevent them from multiplying. Emergence of drug resistance is abig problem in the treatment of infectious diseases like tuberculosis and other lung infections like corona. Therefore scientist community is working in the discovery of new antimicrobial agents. Penicillin, streptomycin, macrolides, azithromycin, fluoroquinolones etc are some examples of common antibiotics. These drugs are also associated with side effects and hence, a hybrid substance that works as a semi synthetic antibiotic, wherein a molecular version produced by the microbe is subsequently modified by the chemist to achieve desired properties of drugs with minimum side effects. Dihydropyridines (DHPs) are reported to have bactericidal activity as it target the biosynthesis of enzymes required for microbial growth. These compounds have both antimicrobial and anticancer activities. Therefore Dihydropyridine derivatives are the new class of compounds found to be active against bacteria and fungi.
Aim of study Dihydropyridine derivatives are known to have prominant activity against many diseases. In this context, the study of its synthesis, characterization and bioevaluation was done to explore the importance of this class of molecules.
Review of Literature
The 1, 4-dihydropyridine nucleus is very common in existing drugs. One of the most common inhibitory activity is that they are calcium channel blockers. Hence, their  ability to relax the vascular smooth muscle, thus decrease the vascular resistance make calcium antagonist potentially useful anti-hypertension drugs. The efficacy of calcium channels blockers is enhanced by the concomitant use of β-adrenergic antagonist, ACEs and methyldopa. Diuretics may be enhanced efficacy of calcium channels blockers [8-9]. Calcium channels blockers have been developed to inhibit the movement of calcium across the membrane of myocardial and smooth muscle, block impulse formation and inhibit the conduction velocity and contraction. As a result,1-4 dihydropyridine derivatives have therapeutics effect in angina, arrhythmias, hyper tension and other cardiovascular disorders.
Some of the derivatives of pyridine are also used as an antimycobactrial agents e.g. isoniazid that is used in the treatment of tuberculosis. Several new derivatives of 1, 4-dihydropyridine have been produced and pharmacologically evaluated in order to find drugs with better pharmacological properties [10-11]. Among them, those with a substituted phenyl ring in the C4 position of the 1, 4-dihydropyridine rings have been found to be more active against diseases.
Dihydropyridines (DHPs) are the feasible heterocyclic ring compounds with different substitutions at several positions. Some 1,4-DHP compounds are reported as antioxidants, antitubercular and drug resistance modifiers [12]. The presence of lipophilic groups in substituted 1,4-dihydropyridines have been reported to have a very good anti-TB activity which makes them an emerging class of antitubercular agents in the area of drug discovery [13]. Substituted 1,4-dihydropyridines have been reported as potent antitubercular agents against Mycobacterium tuberculosisas well as Mycobacterium smegmatis and also possess antimicrobial activity against Bacillussubtilis, E. coli, and Protius vulgaris bacteria [14-15].
Therefore, 1,4 Dihydropyridine derivatives have been synthesized for their pharmacological importance. These are new class of compounds reported to have very potent antibacterial activity against gram-negative bacteria and high antifungal activity against Candida albicans. Such compounds have been investigated for various other bacteria like Staphylococcus epidermis and found to have binding interaction with its protein. Hence, the scientific community found the 1,4 , Dihydropyridine derivatives a new class of compounds as antibacterial and antifungal agents [16-19].
Main Text

The heterocyclic compound 3,5-diacetyl-2,6-di methyl-4-phenyl-1,4- dihydropyridine was synthesized by three component reaction of benzaldehyde, ammonium acetate and Acetyl Acetone (beta-diketo compound) in presence of solvent ethylene glycol , 4A Molecular Sieve, phase transfer catalyst Tetrabutyl ammonim bromide (TBAB) in quantitative yield. Procedure involves in the magnetically stirred slurry of 4Ao molecular sieve (1gm) in ethylene glycol (25ml), acetyl acetone (9.7ml, 94.170mmol) and ammonium acetate (3.63gm, 47.09mmol) was added at room temperature, the reaction mixture was heated up to 60oC and continued for 15 min. and followed by addition of benzaldehyde (5ml, 49.18.mmol) and tetra butyl ammonium bromide (TBAB) as a phase transfer catalyst (700mg) and stirring continued at 65o– 75oC till the benzaldehyde was disappeared. After 2.5 hrs the reaction was completed. The reaction mixture was then poured into the cold water and the precipitate obtained was filtered and dissolved in suitable solvent (chloroform) and anhydrous sodium sulphate (Na2SO4) was then added to absorb the moisture and filtered. The crude product as shown in scheme obtained as coloured oil after evaporation of solvent under reduced pressure and weighed.


Compound-A                    Scheme

The compound-A obtained as colored oil had some impurities which was purified by column chromatography on silica gel column and TLC method was used to monitor the reaction as well as column of the compound. The compound was characterized on the basis of elemental analysis and IR spectroscopy and corresponding data was given in table 1.

 Table 1.   IR Interpretation of compound-A

Sr. No.

l-max (in cm -1)

Types of Vibrations

1.

2927.5

C-H stretching in methyl

2.

2365.8

N-H stretching

3.

1833.1

C=C stretching in pyridine

4.

1696.9

C=O stretching presence of this band indicate the compound may be aldehyde or ketones.

5.

1650.6

C=C  stretching

6.

1548.1

2amide mainly N-H in plane bending.

7.

1461.6

CH2 symmetric bending

8.

1364.2

CH3 symmetric bending

C-N stretching

9.

758.5

A mono substituted benzene

10.

702.3

C-H bending vibration in acetylene or mono substituted acetylene.

 Yield  - 7.54 gm
Molecular formula -  C17H19NO2
Molecular weight - 269.34
Solubility - CHCl3, DMSO, DCM, Ethylacetate.
Physical Appearance- Solid.
Element Detected  -   Nitrogen
Material and Methods:
Bioevaluation:
Synthesized compound-A was evaluated for its Antimicrobial activity. 200 mg /ml (in DMSO) dilution was prepared for this study.
 Microorganism used
Fresh culture of following bacteria & fungi were used in the study:                          
Bacterial Strains
1) E. coli                                   2) Staphylococus aureus 
3) Proteus mirabilis                    4) Bacillus cereus
 Fungal Strains
 1) Aspergillus niger                   2) Aspergillus tereus                                     
 3) Aspergillus japanicus             4) Penicillium chrysogenum

Antimicrobial Assay:                                                    

The agar well diffusion method was used. One ml of diluted innoculum (105CFU/ml) of test organism was mixed on the Muller Hinton agar media (for bacteria) and Sabraud’s agar (for fungus), shaked and pour in sterilized Petri plates. The wells of 8mm diameter were punched into the agar medium. To each well 200mg/ml compound was added and allowed to diffuse, each compound was tested against each organism in triplicate set. The plate were then incubated aerobically 37oC for the bacteria stains for 24 hrs and at 27oC for fungi for 72 hrs.

The antimicrobial activities were then tested for each compound and recorded as diameter of the zone inhibited in mm by our test compound-A. Results obtained against the above bacteria and fungi are discussed in the  Results and Discussions. Antimicrobial activity against the bacteria: Bacillus cereus, Staphylococcus aureus, Proteus, E.coli and Antifungal activity against the fungus: Aspergillus niger, Aspergillus tereus, Penicillium chrysogenum, Aspergillus japanicus are given in table 2 and table 3.

 Table 2.   The Antibacterial activity of compound-A

S. No.

Bacterial species

Gm strain

Concentration

Inhibition zone in (mm)

1.

Bacillus cereus

Gram positive

200mg/ml

16mm

2.

Staphylococcus aureus

Gram positive

200mg/ml

  -

3.

Proteus mirabilis

Gram negative

200mg/ml

 29mm

4.

Escherichia coli

Gram negative

200mg/ml

16mm

 

Result and Discussion

The compound-A is evaluated for antimicrobial activity. Since pyridine and its dihydro-pyridine derivatives are well known to show antibacterial activity. This prompted us to investigate the synthesized compound as possible inhibitor of pathogenic microorganisms. The compound-A was screened against two gram positive i.e. Staphylococcus aureus and Proteus mirabilis and two gram negative bacterial strains i.e. Escherichia coli and Bacillus cereus. The compound-A was dissolved in DMSO (Dimethyl sulfoxide) and a concentration of 200 mg/ml was made and added to the petri plate of each strain. The activity result of compound-A against above mentioned strains is given above in table 2.

The above activity result shown by synthesized compound-A is very encouraging. Compound-A was found to have inhibitory activity against gram negative bacteria. Inhibition zone shown by compound-A, 16 mm, 29mm and 16 mm against Bacillus cereus, Proteus mirabilis and Escherichia coli respectively. However no activity is found against Staphylococcus aureus.

Further the synthesised compound-A was also evaluated for antifungal activity. The fungal strains used as organisms are Aspergillus niger, Aspergillus tereus, Aspergillus japanicus and Penicillium chrysogenum. The compound was dissolved in DMSO and 200mg/ml concentration was made and inoculated to the test organism, after 72 hours a portion of fungal colony was killed by the test sample and this was appeared as clear zone around the test compound-A. This zone was measured in mm scale and the result obtained are 15.5mm (Aspergillus niger), 13mm (Aspergillus tereus), 21mm (Aspergillus japanicus) and  19.3mm (Penicillium chrysogenum) as given below in table 3.

Table 3 .The Antifungal activity of compound-A

S. No.

Test organisms

Concentration of  compound

Zone of inhibition in (mm)

1.

Aspergillus niger

200mg/ml

15.5mm

2.

Aspergillus tereus

200mg/ml

13mm

3.

Penicillium chrysogenum

200mg/ml

19.3mm

4.

Aspergillus japanicus

200mg/ml

 21mm

Conclusion The Dihydropyridine nucleus containing heterocyclic compound-A i.e. (3,5-Diacetyl-2,6-dimethyl-4-phenyl-1,4-Dihydropyridine) was obtained in quantitative yield and it was evaluated for antibacterial and antifungal activity. The maximum inhibition was noticed against the bacterium Proteus mirabilis and better antifungal activity was observed against Aspergillus japanicus.
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