Biocidal activity of some Mannich base cationic derivatives

A novel series of cationic surfactants was prepared based on Mannich base (produced from the condensation of piperidine and/or morpholine as secondary amine and paraformaldehyde in the presence of 8-hydroxyquinoline). The chemical structures of the synthesized cationic surfactants were confirmed using elemental analyses, FTIR spectroscopy and H-1 NMR. Surface activities of the prepared surfactants were measured including: surface tension (gamma), critical micelle concentration (CMC), effectiveness (pi(CMC)), efficiency (Pc-20), maximum surface excess (Gamma(max)), minimum surface area (A(min)), interfacial tension (gamma(IT)), emulsification power and foaming power at 25 degrees C. The structural influences on their surface activities and adsorption free energy were discussed. The synthesized cationic surfactants were evaluated for their biocidal activity towards Gram +ve bacteria (Staph. Cocu., Bacillus), Gram -ve bacteria (Salmonella, E. coli), fungi (A. terrus., A.flav.) and yeast (Candida) at 1.0, 2.5 and 5.0 mg/mL, respectively. The target compounds showed good inhibition towards Gram +ve bacteria, Gram -ve bacteria and yeast. Meanwhile, excellent fungicidal results were obtained against the various types of fungi under investigation. (c) 2005 Elsevier Ltd. All rights reserved.