Biocidal activity of some Mannich base cationic derivatives Original Research Article

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 1H NMR. Surface activities of the prepared surfactants were measured including: surface tension (γ), critical micelle concentration (CMC), effectiveness (πCMC), efficiency (Pc20), maximum surface excess (Γmax), minimum surface area (Amin), interfacial tension (γIT), emulsification power and foaming power at 25 °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.