Synthesis of Certain Schiff Bases of 3-Formyl-2-Quinolones and Evaluation of their Antimicrobial and Antimycobacterial Activities

Prabhakar, K (2017) Synthesis of Certain Schiff Bases of 3-Formyl-2-Quinolones and Evaluation of their Antimicrobial and Antimycobacterial Activities. Masters thesis, Sri Ramakrishna Institute of Paramedical Sciences, Coimbatore.


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INTRODUCTION:Antimicrobial drugs have caused a dramatic change not only of the treatment of infectious diseases but of a fate of mankind. Antimicrobial chemotherapy made remarkable advances, resulting in the overly optimistic view that infectious diseases would be conquered in the near future. However, in reality, emerging and re-emerging infectious diseases have left us facing a countercharge from infections. Infections with drug resistant organisms remain an important problem in clinical practice that is difficult to solve. If an improper antimicrobial agent happens to be chosen for the treatment of infection with drug-resistant microorganisms, the therapy may not achieve beneficial effect, and moreover, may lead to a worse prognosis. In addition, in a situation where multidrug-resistant organisms have spread widely, there may be quite a limited choice of agents for antimicrobial therapy. At present, fewer brand new antimicrobial agents are coming onto the market. Considering this situation together with the increasing awareness of drug safety, we are now facing a situation of severely limited options among antimicrobial agents.PURPOSE AND PLAN OF WORK:Infectious diseases are most devastating diseases all over the world. They are mainly caused by various infectious micro-organisms. All these infections may cause illness and in some cases lead to death of patients. There are many ways to get the infectious diseases, but in all the cases we are not able to prevent the infections that spread. Every year millions of people are prone to infectious diseases and death rate is also getting fluctuation due to the intensity of easily spreading character of the microorganism. To overcome this all the major pharmaceutical companies are involved in extensive research work to generate powerful antibodies against the drastic disease causing agents. Although there are potent antibiotics are present in market. But day to day there is a need for new potent antibiotics, because the microorganism are getting resistant to the drugs by adopting themselves to withstand the potency of the drug ,by mutation, membrane permeability and spore formation. The spread of drug-resistant TB is a man-made tragedy, caused by inadequate or incomplete treatment for decades, old drug regimen that takes atleast six months to cure TB. Drug resistant strains emerge when bacteria are sporadically exposed to existing drugs, or when patients are unable to complete the lengthy and burdensome treatment. Multidrug-resistant TB(MDR-TB)is defined by resistant to atleast two of today’s four standard first-line drugs. The World Health Organization (WHO) estimates that there are nearly a half-million new cases of MDR-TB each year. These cases are difficult to manage and have much lower cure rates. For MDR-TB patients, treatment can take upto 2 years, with second line drugs that are more expensive, do not always work, and have significant side effects.SUMMARY:With the view of synthesizing new compounds with minimum side effects, less toxicity, non-resistant and more selective against disease-producing microorganisms, the present work was undertaken to synthesize 8 different Schiff bases of 3-formyl-2-quinolone and substitutes of 3-formyl-2-quinolones with isoniazid. LITERATURE REVIEW The extensive literature reports showed that the Schiff bases of 3-formyl- 2- quinolones are potent antimicrobial agents. The 2-Quinolone moiety and Schiff bases posses excellent antimicrobial activity. SCHEME: All the intermediate and final compounds are synthesized by traditional method. STEP 1: Initially Acetanilde and substituted acetanilides were prepared by refluxing aniline and substituted anilies with acetic acid and zinc dust. STEP 2: 2-chloro-3-formyl quinoline and substituted 2-chloro-3-formyl quinolines were synthesized from acetanilide and substituted acetanilides correspondingly using Vilsmeier Haack reaction. STEP3: The synthesized compounds were refluxed with a 70% acetic acid to give 3-formyl-2-quinolone and substituted 3-formyl-2-quinolones STEP4: Finally, 3-formyl-2-quinolone and substituted 3-formyl-2-quinolones were refluxed with isoniazid in presence of ethanol and concentrated sulphuric acid to get different Schiff bases. SPECTRAL STUDIES:Structures of all the newly synthesized compounds were confired by UV,IR, MASS and NMR.CONCLUSION:Based on the results of synthetic works, characterization data, antimicrobial screening and antimycobacterial screening the following conclusions were made. Using the schemes evolved, eight different Schiff bases of 3-formyl-2-quinolone and substituted 3-formyl-2-quinolones were synthesized in good yields. Four synthesized derivatives (5a,5b,5f,5g) showed equipotent antitubercular activity compared to the standard streptomycin at concentration of 6.12μg/ml. Compound 5c showed equipotent antitubercular activity compared to the standards Pyrazinamide and Ciprofloxacin at concentration of 3.125μg/ml The synthesized compounds showed poor to moderate antibacterial activity. The in vitro antimicrobial studies showed that three of eight compounds exhibited good antibacterial activity in which compound 5c showed the highest activity against Bacillus subtillis NCIM 2063 and Pseudomonas aeruginosa NCIM 2036. The compounds 5b,5c,5f,5g exhibited the highest antifungal activities.

Item Type: Thesis (Masters)
Additional Information: REGISTRATION No.261515104
Uncontrolled Keywords: Schiff Bases ; 3-Formyl-2-Quinolones ; Antimicrobial ; Antimycobacterial Activities
Subjects: PHARMACY > Pharmaceutical Chemistry
Depositing User: Ravindran C
Date Deposited: 16 Mar 2018 06:04
Last Modified: 16 Mar 2018 06:04

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