KIMIKA Volume 29, Number 2, pp. 23-29 (2018) © 2018 Kapisanang Kimika ng Pilipinas All rights reserved. Printed in the Philippines. ISSN 0115-2130 (Print); 2508-0911 (Online) https://doi.org/10.26534/kimika.v29i2.23-29 Lipophilic halogen-free ionic liquid with antibacterial and anti-bioflm activities against Pseudomonas aeruginosa Kris Corinne DC. Laserna 1 , Christian Deo T. Deguit 1 , Wilfred F. Ong 1 , and Drexel H. Camacho 1,2* 1 Chemistry Department, De La Salle University, 2401 Taft Avenue, 0922 Manila 2 Organic Materials and Interfaces Unit, CENSER, De La Salle University, 2401 Taft, Avenue, Manila ABSTRACT A halogen-free ionic liquid (IL) designed with long alkyl chain anion is reported. 1-methylimidazolium stearate (MIM stearate) synthesized through Bronsted acid-base reaction has shown improved lipophilic character and indications penetrate bacterial cell walls. Antimicrobial activities against Gram-negative bacteria, Escherichia coli, and Pseudomonas aeruginosa were observed. Anti-bioflm assays showed efectivity against the bioflm of Pseudomonas aeruginosa. At 50 µg/mL the %bioflm inhibition of MIM stearate towards P. aeruginosa bioflm formation is comparable to the Bromofuran positive control. Brine shrimp lethality assay showed weak toxicity indicating the IL to be safe and benign. Te synthesized MIM stearate showed good promise as an antimicrobial and anti-bioflm agent. Keywords: ionic liquid; imidazolium stearate; halogen-free ionic liquid; antimicrobial; anti-bioflm; lipophilic INTRODUCTION Bioflm, a group of microorganisms encased in an extracellular polymeric substance (EPS) is a survival strategy for microbial populations. It poses an industrial, environmental, health and economic hazard because bioflms cannot be removed by gentle rinsing afecting the form, ft and function of the substrates they attached unto. Moreover, the EPS, a gel matrix made up of polysaccharides, proteins, lipids, and other macromolecules holds the microorganisms together making them resistant to antimicrobial treatments (Flemming 1996; Bridier et al. 2011). Bioflm-mediated complications such as functional failures of implanted medical devices, biocorrosion of industrial structures and chronic infection to humans, animals, and plants, have been a major problem (Lewis, 2001; Costerton & Wilson, 2004). Tus the efcient control of microbial bioflms is of particular interest. Tere has been an active search for potent compounds that can efectively inhibit bioflm formation. However, efective anti-bioflm agents that are safe and environmentally benign are hard to fnd. Plant extracts (Kodali et al. 2013; Upadhyay et al. 2013; Viju et al. 2013, Riihinen et al. 2014) and bacterial polysaccharides (Bernal & Llamas 2012; Karwacki et al. 2013; Kavita et al. 2014) have been reported to inhibit bioflm formation but the mechanism is unknown. Nanoparticles (Kanmani & Lim, 2013; Lee et al. 2014; Taglietti et al. 2014) and enzymes (Burton et al. 2006; Gawande et al. 2011) have been reported to alter the extracellular polymeric substance (EPS) in bioflms making it susceptible to antimicrobial treatments. A simple compound that can penetrate into the EPS and deliver the active *Author to whom correspondence should be addressed; email: drexel.camacho@dlsu.edu.ph