SYNTHESIS AND ANTIMICROBIAL EVALUATION OF 4-BENZYLIDENE- PYRAZOLIDINE-3, 5-DIONE DERIVATIVES

SYNTHESIS AND ANTIMICROBIAL EVALUATION OF 4-BENZYLIDENE- PYRAZOLIDINE-3, 5-DIONE DERIVATIVES

Harish Kumar* and Sandeep Jain

Drug Design and Research Laboratory, Department of Pharmaceutical Sciences, Guru Jambheshwar University of Science & Technology, Hisar-125001, Haryana, India

ABSTRACT

In the present research work, diethyl malonate and phenyl hydrazine were reacted together to give pyrazolidine-3,5-dione nucleus which was further derivatized at fourth position by reacting with different aromatic aldehydes to give 4-benzylidene-pyrazolidine-3,5-diones, followed by the 4-chloro-butyl and 4-nitrooxy-butyl substitution at nitrogen atom. The synthesized products were characterized by physicochemical and analytical means. Few of the synthesized derivatives showed excellent antibacterial and antifungal activities.

Pyrazole, 1,2-diazoles, Synthesis, Antimicrobial, Antibacterial, Antifungal

INTRODUCTION: Pyrazole, also known as 1, 2-diazole ¹, belonging to one of the most important classes of heterocycles, has been considered to be pharmacologically very important nucleus owing to the potent and broad spectrum activity of the pyrazole scaffold.

It has been the topic of research for thousands of researchers all over the world because of its wide spectrum activities like anti-inflammatory, antipyretic, analgesic ², antitubercular ³, antiviral ⁴, anti hypertensive ⁵, antiglaucoma ⁶, antioxidant ⁷, anti depressent, anxiolytic, neuroprotective ⁸, antimicrobial ⁹, cytotoxic, antiproliferative ¹⁰, antidiabetic ¹¹, anticancer ¹² and anti-alzheimer ¹³.

Several methods have been reported in literature for the synthesis of pyrazoles. Most common method of pyrazole synthesis is the reaction between 1, 3-diketocompounds and hydrazine or hydrazine hydrate or substituted hydrazines ¹⁴.

Wang et al., reported the synthesis of 1, 3, 4, 5-tetrasubstituted pyrazoles taking hydrazonyl chlorides and 2-azidoacrylates as reactants using triethylamine as base ¹⁵.

Antipyretic action of a pyrazole derivative in man was discovered by Knorr,in 1884 and the compound was named “antipyrine”.

Pyrazolones and 1-phenyl-Pyrazolidine-3,5-diones are the most important derivatives of pyrazole and are present as a basic moiety in a number of pharmaceutical compounds like Phenylbutazone, oxyphenbutazone, butazolidine, antipyrine, amino-pyrine and novalgin.

MATERIALS AND METHODS: The reagent grade chemicals were obtained from commercial sources and were purified by either recrystallization or distillation before use. Melting points were determined by decibel melting point apparatus and were uncorrected. All reactions were monitored by thin layer chromatography (TLC) using silica gel G (Spectrochem Pvt. Ltd., Mumbai).

The plates were developed by exposing to iodine chamber. Infrared spectra were recorded by FTIR-ATR Thermo Scientific NICOLET Is10 spectrophotometer using KBr disks. Proton nuclear magnetic resonance spectra (¹H-NMR) were recorded on Bruker Avance П 400 NMR Spectrophotometer using DMSO as solvent from Central laboratory, Punjab University, Chandigarh. Chemical shifts are expressed as δ values (ppm).

Synthetic Procedure: The general scheme for the synthesis of 4-Benzylidene-Pyrazolidine-3,5-dione derivatives has been represented in Figure 1.

Step 1. Synthesis of Parent Compound (1-Phenyl-pyrazolidine-3, 5-diones): Heated a mixture of 0.01 M (1.60 mL) Diethyl malonate and 0.01 M (1.08 mL) Phenyl hydrazine at 120^oC on an oil bath for 1 hour with constant stirring followed by cooling the resulting red oil and stirring with 20 mL ether until solidification occurs, the product was filtered and washed with 20 mL ether. The resultant compound was recrystallized using 50% aqueous ethanol. Melting point measurement was done. The formation of the parent compound was then confirmed by performing TLC using Chloroform:Methanol (10:10) as mobile phase. Spots were identified by placing the plates in iodine chamber and R_f value was calculated.

Step 2. Synthesis of 4-Benzylidene-1-Phenyl-pyrazolidine-3, 5-diones: To a mixture of 0.01 M 1-Phenyl-pyrazolidine-3, 5-diones, was added 0.01 M of substituted Benzaldehyde using 0.01 M weak base. The mixture was refluxed for 2 hours. The solution thus obtained was cooled by keeping over ice or cold water. After cooling colored solid mass was separated and recrystallized using ethanol. Crystals so obtained were dried and melting point was determined followed by the TLC using Chloroform:Methanol (10:10) as mobile phase.

Step 3. Synthesis of 4-Benzylidene-1-(4-chloro-butyl)-2-Phenyl-pyrazolidine-3, 5-diones: A mixture of 0.01 M of 4-Benzylidene-1-Phenyl-pyrazolidine-3, 5-diones with 0.008% v/v 1, 4-dichlorobutane in dried toluene was refluxed using 0.01 M triethylamine as base. The assembly was protected by anhyd.CaCl₂ dry tube for about 8-10 Hours, after refluxing excess solvent was distilled off and remaining solution was filtered; residue was kept overnight and dried by keeping in a desiccator.

Step 4. Synthesis of 4-Benzylidene-1-(4-nitrooxy-butyl)-2-Phenyl-pyrazolidine-3, 5- diones: Final product was synthesized by dissolving 0.01 M 4-Benzylidene-1-(4-chloro-butyl)-2-Phenyl-pyrazolidine-3, 5-diones in 0.015 % w/v Silver nitrate in dried benzene. The resultant solution was heated for 2 hours. After refluxing, excess solvent was distilled off. Remaining solution was cooled; crystals were filtered, kept overnight and dried by keeping in a desiccator.

Table 1 and Table 2 respectively represent the list of synthesized 4-Benzylidene-Pyrazolidine-3, 5-dione derivatives and their physicochemical characterization. The antimicrobial activity (MIC values) of4-Benzylidene-Pyrazolidine-3, 5-dione derivatives for various bacterial and fungal strains has been enlisted in Table 3.

FIGURE 1: GENERAL SCHEME FOR THE SYNTHESIS OF 4-BENZYLIDENE-PYRAZOLIDINE-3,5-DIONE DERIVATIVES

TABLE 1: LIST OF 4-BENZYLIDENE-PYRAZOLIDINE-3,5-DIONE DERIVATIVES SYNTHESIZED

TABLE 2: PHYSICOCHEMICAL CHARACTERIZATION OF SYNTHESIZED 4-BENZYLIDENE-PYRAZOLIDINE-3,5-DIONES DERIVATIVES

 RESULTS AND DISCUSSION:

Evaluation of Antimicrobial Activity:

1. Antibacterial activity: Synthesized 4-benzylidene pyrazolidine-3, 5-dione derivatives (CN-1 to CN-21) were tested in vitro for their antibacterial profile using Tube Dilution Method ^{16, 17} against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa. MIC values were calculated for all the synthesized compounds using Ciprofloxacin as the standard. The tested solutions were serially diluted to give concentrations of 5, 2.5, 0.125, 0.625, 0.312 mg/mL respectively.  All the microbial strains were procured as lyophilized form from Himedia Labs Pvt. Ltd, Mumbai.
2. Antifungal activity: Antifungal activity evaluation of synthesized compounds against Candida albicans were performed similar to antibacterial activity by use of Sabouraud’sglucose broth as media for assay taking Fluconazole as the standard drug. MIC wasdetermined by the lowest concentration of sample that prevented the development ofturbidity.

TABLE 3: ANTIMICROBIAL ACTIVITY (MIC VALUES) OF 4-BENZYLIDENE-PYRAZOLIDINE-3, 5-DIONE DERIVATIVES

CONCLUSION: A novel class of 4-benzylidene-pyrazolidine-3, 5-diones were synthesized and characterized for their structure activity relationship. Antibacterial and Antifungal studies of these compounds indicated that the compounds CN-3, CN-10 and CN-12 were found to be the most active antibacterial compounds. Compounds CN-3, CN-10 and CN-12 showed potent antibacterial effect against gram positive bacteria. Compounds CN-11, CN-17, CN-18 and CN-19 showed potent antibacterial effect against gram negative bacteria. Compounds CN-5, CN-7, CN-8, CN-20 were found to possess better antifungal activity than antibacterial.

ACKNOWLEDGEMENTS: The authors express gratitude to the in-charge, SAIF, Punjab University, Chandigarh for recording the ¹H-NMR. The authors also express their sincere thanks to All India Council of Technical Education, New Delhi for financial support.

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    How to cite this article:

    Kumar H and Jain S: Synthesis and Antimicrobial evaluation of 4-benzylidene- pyrazolidine-3, 5-dione derivatives.  Int J Pharm Sci Res. 2013; 4(1); 453-457.

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