Anti-Infective Agents   Rohit Singh * and Swastika Ganguly Department of Pharmaceutical Sciences, Birla Institute of Technology, Mesra, Ranchi-835215, Jharkhand, India Abstract: Introduction: A series of seventeen 1-phenyl-3-(5-phenyl-1H-imidazol-1-yl) thiourea deriva- tives (5a-8d) were synthesized and characterized by physical and spectral data (IR, 1H NMR, and mass spectroscopy) and evaluated for their antibacterial and antifungal activities against various pathogenic and non-pathogenic microorganisms. Some of the synthesized compounds showed promising antibacte- rial and antifungal activities. Results and Discussions: Many of the tested compounds were found to be significantly active against gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacterial strains (Escherichia coli, Salmonella typhi, Klebsiella pneumoniae and Pseudomonas aeruginosa), among which compounds 5a, 5b, 6a, 6b, 7a, 7b, 8a and 8b showed the maximum anti-bacterial activity but less effective than the standard ciprofloxacin. Almost all compounds from 5a-8d showed moderate activity against fungal strains like Candida albicans and Aspergillus niger. A R T I C L E H I S T O R Y Received: August 28, 2017 Revised: February 26, 2018 Accepted: February 28, 2018 DOI: 10.2174/2211352516666180307155830 Keywords: Imidazole derivatives, synthesis, antibacterial, antifungal activities, Anti-Microbial, Staphylococcus aureus. 1. INTRODUCTION Earlier works in our laboratory have been identified as various substituted imidazole derivatives exhibiting broad- spectrum chemotherapeutic properties [1-3]. In continuation of our effort to develop imidazoles as broad-spectrum chemotherapeutic agents, the present study was undertaken to synthesize and evaluate novel imidazoles for antibacterial and antifungal activities. Antibiotics have been an important class of agents which have turned the tide regarding treatment of infectious diseas- es. The overwhelming success of antibiotics in therapy has made them one of the most important products in the drug industry today [4]. Antibiotics have also prompted the expan- sion of their use in several related fields. However, the nor- mal biological processes of microbial pathogens are varied and complex. Thus, the increased use of antibiotics has led to microbial resistance, and the development of newer and safer antibiotics has become very important in providing the means for treating resistant strains of organisms that had been pre- viously susceptible to an older antibiotic. In recent years, due to the repeated use of antibacterial antibiotics, the use of im- mune suppressive agents, cytotoxins, irradiation fungal infec- tions have proved to become a continuous and serious threat *Address correspondence to this author at the Department of Pharmaceutical Sciences and Technology, Birla Institute of Technology and Sciences, Mesra, Ranchi, India; Tel: 09454116086; E-mail: rohitsingh20485bitmesra@gmail.com to human health and their life [5]. Azoles are a class of heter- ocycles which have attracted significant interest in medicinal chemistry and they have a wide range of pharmaceutical and biological activities including antimicrobial, anti-fungal, anti- inflammatory, and antihypertensive [6-8]. The widespread use of 1,3,4-oxadiazoles, such as Imidazoles, is considered well-known for heterocyclic com- pounds which have been established in the clinical practice as various medicinal agents. Imidazoles and their derivatives have been reported as biological active constituents in many of the major biological systems with a broad range of phar- macological activities against various organisms. They are well known as proton donors as well as proton acceptors in various enzymatic reactions which are the basis for charge transfer on various enzymatic reactions [9, 10], as well as antibacterial [11, 12], antiviral, antiHIV, antiparasitic [13], antiepileptic [14], anti-inflammatory and anticancer agents [15-18]. Geeta et al. synthesized 26 novel benzimidazole com- pounds were having alkyl chain as linker at N-1 position and synthesized, evaluated to investigate their possible anti-HIV and antimicrobial activities [19]. De Martino et al. [20] de- veloped various substituted imidazoles as broad-spectrum chemotherapeutic agents and in continuation of his work, we undertook the present study to synthesize and evaluate novel imidazole thiourea derivatives as potent antimicrobial and antifungal agents. 2211-3533/18 $58.00+.00 © 2018 Bentham Science Publishers Send Orders for Reprints to reprints@benthamscience.ae 64 Anti-Infective Agents, 2018, 16, 64-70 RESEARCH ARTICLE Synthesis, Anti-Microbial Evaluation and Structure Activity Relationship (SAR) Studies of Some 1-phenyl-3-(5-phenyl-1H-imidazol-1-yl) thiourea Derivatives