ORIGINAL RESEARCH In vitro antimicrobial assessment of coumarin-based s-triazinyl piperazines Divyesh Patel • Rahul Patel • Premlata Kumari • Navin Patel Received: 18 January 2011 / Accepted: 18 May 2011 / Published online: 1 June 2011 Ó Springer Science+Business Media, LLC 2011 Abstract A series of 1,3,5-triazine derivatives that contain aniline, coumarins (4-hydroxy coumarin and 7-hydroxy-4- methyl coumarin) and different piperazine moieties as sub- stituent on the carbon atoms of the triazine ring have been synthesized by a simple and efficient synthetic protocol. Comparative studies were performed on above series, which were synthesized with conventional and microwave heating methods. The microwave method was observed to be more beneficial as it provides an increase in yield and 90–95% reduction time. All the synthesized compounds were then examined for their efficacy against two Gram -ve bacteria (Escherichia coli and Pseudomonas aeruginosa), two Gram ?ve bacteria (Staphylococcus aureus and Bacillus subtilis) and two fungal species (Candida albicans and Aspergillus niger) with an intent to overcome multiple drug resistance to the pathogenic strains. All the synthesized compounds were structurally elucidated by IR, 1 H NMR, 13 C NMR and ele- mental analysis. Keywords 1,3,5-Triazines Á Coumarins Á Piperazines Á Microwave irradiation Á Antimicrobial Introduction During the past few decades, 1,3,5-triazines have been grabbing the attention of the synthetic chemists for their wide gamut of biological activities, such as antimicrobial (Zhou et al., 2008; Srinivas et al., 2006), antiprotozoal (Alessandro et al., 2005), anticancer (Rita et al., 2004), antimalarial (Sergio et al., 2008) and antiviral (Yuan-Zhen et al., 2008) activity. Recently, a series of some new s-triazine analogues incorporating p-cyano aniline and 8-hydroxyquinoline substitutions were designed and syn- thesized by our group (Rahul et al., 2010). These com- pounds showed good to excellent in vitro antimicrobial activity against most of the tested pathogenic microbes, representing a promising lead for further optimization. To extend their structure–activity relationships (SARs), we have designed and synthesized a novel series based on the modification of some structural units as p-cyano aniline was replaced by simple aniline and 4-hydroxyquinoline has been replaced by 4-hydroxycoumarin as well as 7-hydroxy- 4-methyl coumarin. We have introduced the similar piperazine bases to both of the systems in an order to identify the difference between the biological profiles of the resultant series, in which activity was found to be increased against most of studied strains of bacteria and fungi in terms of MIC. The coumarins are heterocyclic organic compounds, also known as benzo-2-pyrone deriv- atives and mainly found in plants of the family of Rutaceae and Umbelliferae (Dekic ´ et al., 2007). Natural and syn- thetic coumarin derivatives represent an important group of organic compounds that are used as antibiotics (Estevez- Braun and Gonzalez 1997; Hussain et al., 2003), fungicides (Satyanarayana et al., 2008; Khalid et al., 2004), anti- inflammatory (Anne et al., 2001; Khalid et al., 2010), anticoagulant (Manolov and Danchev 1995), antitumor (Raev et al., 1990), anti-urease (Zaheer-ul-Haq et al., 2008), antileucemic (kotali et al., 2008), antioxidant and insecticidal agents (Khan et al., 2002) and also showing cytotoxic property (Ronad et al., 2010; Muhammad et al., D. Patel Á R. Patel Á P. Kumari (&) Applied Chemistry Department, S.V. National Institute of Technology, Surat 395007, India e-mail: premlatakumari@gmail.com N. Patel Department of Chemistry, V.N. South Gujarat University, Surat 395007, India 123 Med Chem Res (2012) 21:1611–1624 DOI 10.1007/s00044-011-9676-3 MEDICINAL CHEMISTR Y RESEARCH