|Year : 2013 | Volume
| Issue : 2 | Page : 80-83
Synthesis and evaluation of anti-tubercular activity of some novel 2-pyrazoline derivatives
Shivakumar M Hipparagi1, Mahesh D Bhanushali2
1 Department of Pharmaceutical Chemistry, KLE University's College of Pharmacy, Rajajinagar, Bangalore, Karnataka, India
2 Department of Pharmaceutical Chemistry, Maratha Mandal's College of Pharmacy, Belgaum, Karnataka, India
|Date of Web Publication||23-Jul-2013|
Shivakumar M Hipparagi
Department of Pharmaceutical Chemistry, KLE University's College of Pharmacy, 4th T Block, Rajajinagar, Bangalore, Karnataka
Source of Support: None, Conflict of Interest: None
Purpose: Pyrazolines and its derivatives are reported to possess a wide spectrum of biological activities. Many class of chemotherapeutic agents containing pyrazoline nucleus are in clinical use. The purpose of this present study was to examine whether the molecular modification might result in detection of new potent anti-tubercular agent. Materials and Methods: A series of 2-pyrazoline compounds (P13-P24) have synthesized by treating N-(substituted aryl)-acrylamide (C13-C24). The starting material was synthesized from substituted P-aminoacetophenone and substituted benzaldehyde. Their structure was confirmed by infrared and 1 H NMR spectral data. The synthesized compounds were screened for anti-tubercular activity by Microplate Alamar Blue Assay method. Results: Compound P 15 and P 20 have shown excellent anti-tubercular activity; compound P 16 and P 22 have shown significant activity as compared with the standard and rest of them have shown moderate to low anti-tubercular activity. Conclusion: These compounds may result in the potent anti-tubercular entity with molecular modification and manipulations.
Keywords: Anti-tubercular activity, minimum inhibitory concentration, pyrazoline
|How to cite this article:|
Hipparagi SM, Bhanushali MD. Synthesis and evaluation of anti-tubercular activity of some novel 2-pyrazoline derivatives. J Sci Soc 2013;40:80-3
| Introduction|| |
Tuberculosis is the most prevalent communicable infectious disease on earth and remains out of control in many developing countries. Recently, available therapy to control the tuberculosis is somewhat challenging in case of multi-drug resistance strains of mycobacterium tuberculosis, together with the increased incidence of severe disseminated infectious produced by mycobacterium other than tuberculosis, particularly mycobacterium avium in immunocomprised patients  has prompted the search for new chemical entity having more potent and fewer side effects to tackle the current situation.
From literature survey, in recent years pyrazolines have attracted considerable interest because of their therapeutics and the pharmacological properties such as antibacterial,  antifungal,  antiviral,  anti-tubercular,  antiamoebic,  anticancer,  anti-inflammatory,  analgesic,  antidepressant,  and anticonvulsant  activity. Hence, it was planned to synthesize a novel series of 2-pyrazoline derivatives and evaluate for anti-tubercular activity.
| Materials and Methods|| |
Melting points were determined in open capillary tube and are uncorrected. All the chemicals were obtained of analytical grade purity. The infrared (IR) spectra were recorded on a JASCO Fourier Transform Infrared Spectrometer (FTIR)-460 (JASCO International Co. Ltd. Japan) using the KBr disc method. Proton Nuclear Magnetic Resonance (1H-NMR) Spectroscopy were recorded on Bruker Avance II 400 Nuclear Magnetic Resonance (NMR) spectrometer using the Dimethyl sulfoxide (DMSO)/Chloroform-d (CDCl 3 ) as solvent and TMS as an internal standard. All the chemical shift are expressed in δ ppm.
General procedure for synthesis of N-(4-substituted phenyl)-3-(4-substituted phenyl)-acrylamide (C 13 -C 24 )
A mixture of substituted acetoaminophenone (0.01 mol) and substituted benzaldehyde (0.01 mol) in ethanol (25 ml) were stirred together in presence of 20% NaOH solution (40 ml) for 5-6 h. The mixture was kept in refrigerator overnight. The crystals obtained were washed with water until the solution become neutral to litmus paper and recrystallized from suitable solvents. Other compounds (C 13 -C 24 ) were synthesized similarly. 
C 15 :IR (KBr): 3301.8 (NH str), 3036.34 (Ar C-H str), 1694.9 (C = O str), 1579.3 and 1396.8 (NO 2 -C str), 1521.3 (C = C str). 1 H NMR (CDCl 3 ) 7.20-7.22 (d, 1H, =CH), 7.67-7.69 (d, 1H, =CH), 8.08-8.16 (m, 9H, Ar-H), 8.61 (s, 1H, NH).
General procedure for synthesis of (4- substituted phenyl)-[5-(4-substituted phenyl)-1-phenyl-4,5-dihydro- 1H-pyrazol-3-yl]-amine (P 13 -P 24 )
A mixture of N-(4-substituted phenyl)-3-(4-substituted phenyl)- acrylamide (0.01 mol) in 30 ml of ethanol and phenyl hydrazine (0.01 mol) in the presence of few drops of glacial acetic acid, were refluxed for 4-6 h. The reaction mixture was poured into cold water and the product, which separated was filtered and recrystallized from suitable solvent.  Other compounds (P 13 -P 24 ) were synthesized similarly and their physical data are given in [Table 1].
|Table 1: Physical and analytical data of synthesized compounds (P13-P24)|
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P 15 : IR (KBr): 3342.89 (NH str), 3066.33 (Ar C-H str), 2923 (C-H str), 1596.61 (C = N str), 1502.94 and 1330.55 (NO 2 -C str). 1 H NMR (CDCl 3 ), 2.17 (d, 1H, CH), 2.67-2.68 (d, 1H, CH 2 ), 3.67-3.68 (d, 1H, CH 2 ), 3.97 (s, 1H, NH). 7.24-7.64 (m, 14H, Ar-H).
The anti-tubercular screening was carried out by Middle brook 7H9 broth against Mycobacterium tuberculosis of H37Rv strain. The minimum inhibitory concentration (MIC) of each synthesized compound was determined by Microplate Alamar Blue Assay (MABA) and is defined as the lowest concentration of drug, which inhibits ≤99% of bacterial population present at the beginning of the assay. This method is non-toxic and shows good correlation with BACTEC radiometric method  . Briefly, 200 μl of sterile deionzed water was added to all outer perimeter wells of sterile 96 wells plate to minimized evaporation of medium in the test wells during incubation. The 96 wells plate received 100 μl of the Middlebrook 7H9 broth and serial dilution of compounds were made directly on plate. The final drug concentrations tested were 0.01-20.0 μl/ml. Plates were covered and sealed with the parafilm and incubated at 37°C for 5 days. After this time, 25 μl of freshly prepared 1:1 mixture of Almar Blue reagent and 10% tween 80 was added to the plate and incubated for 24 h. A blue color in the well was interpreted as no bacterial growth, and pink color was scored as growth. The MIC was defined as the lowest drug concentration, which prevented the color change from blue to pink. Isoniazid was used as standard drug.
| Results and Discussion|| |
The main aim of this work was to synthesize some novel (4-substituted phenyl)-[5-(4-substituted phenyl)- 1-phenyl-4,5-dihydro-1H-pyrazol- 3-yl]-amine (scheme) [Figure 1] derivatives. Initially, N-(4-substituted phenyl)-3-(4-substituted phenyl)-acrylamide (chalcones C 13 -C 24 ) was synthesized from the reaction of substituted acetoaminophenone and substituted benzaldehyde in ethanol in presence of NaOH. The titled compounds (2-pyrazoline P 13 -P 24 ) were obtained by refluxing the chalcones and phenyl hydrazine in presence of catalytic amount of glacial acetic acid.
The titled synthesized compounds were tested for their anti-tubercular activity in-vitro against isoniazid resistance mycobacterium tuberculosis, using MABA method. The results are shown in [Table 2]. The standard isoniazid has shown 0.2 MIC μg/ml. None of the compound was found to be equipotent with standard isoniazid. Among 12 titled synthesized compounds P 15 and P 20 have shown excellent activity; as there is introduction of Para-nitro group (P 15 ), Para-chloro and Para-hydroxyl group (P 20 ) in aryl moiety of the 2-pyrazoline analogs. Compound P 16 and P 22 have shown significant activity and lesser than the compound P 15 and P 20 as there is introduction of para-fluoro (P 16 ) and para-bromo (P 22 ) along with para-chloro, which have decreased the activity due to electro negativity. And rest of them has shown moderate to low activity.
| Conclusion|| |
The results of anti-tubercular activity of all the tested compounds were reported as MIC (μg/ml). The results revealed that most of the newly synthesized compounds exhibited significant to moderate activity. Compound P 15 and P 20 have shown excellent activity at MIC values of 1.6 μg/ml and all other compounds exhibited activity at MIC values of 3.12-100 μg/ml. The method used to study anti-tubercular activity known as MABA is rapid and low-cost as compared with other methods.
We have come to a conclusion that with molecular modification and manipulations, these compounds may result in the potent anti-tubercular entity.
| Acknowledgment|| |
Authors are thankful to the principal, Maratha Mandal's College of Pharmacy, Belgaum and Nathajirao Halgekar Institute of dental sciences, Belgaum for providing the necessary facilities to carry out the research work.
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[Table 1], [Table 2]