ORIGINAL RESEARCH Synthesis and anti-biofilm activity of thiazole Schiff bases Prakash G. More • Netaji N. Karale • Anjana S. Lawand • Naina Narang • Rajendra H. Patil Received: 17 March 2013 / Accepted: 4 June 2013 Ó Springer Science+Business Media New York 2013 Abstract A series of thiazole Schiff bases (SB-1 to SB-7) have been synthesized by reacting 4-(o-methoxyphenyl)-2- aminothiazole and R substituted salicylaldehyde (R = H, 3-Me, 4-Me, 5-Me, 3-OMe and 5-Br) or 2-hydroxy-1-naph- thaldehyde under microwave irradiation (a green chemistry approach). The compounds were characterized by spectral (UV–Vis, IR, 1 H NMR, 13 C NMR and GC–MS) and thermal analyses, and tested for the evaluation of anti-biofilm activity against Pseudomonas aeruginosa and anti-bacterial activity against Gram positive (Bacillus subtilis NCIM 2063) and Gram negative (Escherichia coli NCIM 2931) bacteria. The scanning electron microscopic images of the bacterial sur- faces have shown that the Schiff bases have impeded the biofilm formation at 50–100 lg/mL concentration, without affecting the growth of the cells (and thus behave as an- tiquorum sensing agents). Confocal laser scanning micros- copy has also confirmed the biofilm inhibition. The anti- biofilm and anti-bacterial activities of the Schiff bases are promising in the design and bio-fabrication of medical devices to combat the biofilm-forming pathogenic organisms. Keywords Quorum sensing Á Biofilm Á Schiff Bases Á Anti-bacterial Introduction Treatment of emerging infectious diseases and the increasing number of multidrug resistant microbial pathogens are the taunting tasks in the medical community (Dessen et al., 2001; Tenover and McDonald, 2005; Muroi et al., 2004; Pfeltz and Wilkinson, 2004; Roberts, 2004). The search for an effective compound to combat bacterial pathogenicity is the need of an hour. Thiazoles are well known as biologically active compounds and exhibit several biological activities such as anti-hypertensive, anti-inflammatory, anti-bacterial, anti-HIV, anti-tumor and cytotoxic activity (Kashyap et al., 2012). Schiff bases derived from aminothiazoles have been shown to possess anti-bacterial and anti-fungal activities (More et al., 2001). The anti-bacterial activity of different types of Schiff bases is also well reported. Karthikeyan et al. (2006) have synthesized Schiff bases (with a 2,4-dichloro-5-fluor- ophenyl moiety) exhibiting anti-microbial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia. Shi et al. (2007) have synthesized a series of Schiff bases by reacting 5-chloro-salicylaldehyde and primary amines, and evalu- ated their anti-bacterial activity against Bacillus subtilis, E. coli, P. fluorescence and S. aureus. Sinha et al. (2008) have synthesized eight novel heterocyclic Schiff bases derived from the condensation reactions of indole 3-car- boxaldehyde with different l-amino acids (histidine, glu- tamic acid, aspartic acid, leucine, valine) as well as with some aminophenols, and these compounds were found to exhibit anti-bacterial activity against B. subtilis, P. fluo- rescence, S. aureus. Kamaria et al,(2011) have reported a series of Schiff bases (derived from indole-3-aldehyde by microwave-assisted synthesis), which were active against S. aureus and B. subtilis. However, synthesis of present P. G. More (&) Á A. S. Lawand School of Chemical Sciences, Solapur University, Solapur 413255, Maharashtra, India e-mail: pramore01@yahoo.com N. N. Karale Vidya Pratishthan’s Arts, Science and Commerce College, Baramati 413133, Maharashtra, India N. Narang Á R. H. Patil Department of Biotechnology, University of Pune, Pune 411007, Maharashtra, India 123 Med Chem Res DOI 10.1007/s00044-013-0672-7 MEDICINAL CHEMISTR Y RESEARCH