title: A study of the antibacterial activity of L-phenylalanine and L-tyrosine esters in relation to their CMCs and their interactions with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC as model membrane.
abstract: Cationic amino acid-based surfactants are known to interact with the lipid bilayer of cell membranes resulting in depolarization, lysis and cell death through a disruption of the membrane topology. A range of cationic surfactant analogues derived from L-Phenylalanine (C1-C20) and L-Tyrosine (C8-C14) esters have been synthesized and screened for their antibacterial activity. The esters were more active against gram positive than gram negative bacteria. The activity increased with increasing chain length, exhibiting a cut-off effect at C12 for gram positive and C8/C10 for gram negative bacteria. The cut-off effect for gram negative bacteria was observed at a lower alkyl chain length. The CMC was correlated with the MIC, inferring that micellar activity contribute to the cut-off effect in antibacterial activity. The interaction of the cationic surfactants with the phospholipid vesicles (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC) in the presence of 1-anilino-8-naphthalene sulfonate (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescence probes showed that an increase in ionic interaction causes an increase in antibacterial activity. Increase in hydrophobic interaction increases the antibacterial activity only to a certain chain length, attributing to the cut-off effect. Therefore, both electrostatic and hydrophobic interactions, involving the polar and nonpolar moieties are of paramount importance for the bactericidal properties.
authors.affiliation: Department of Chemistry, Faculty of Science, University of Mauritius, Reduit, Mauritius.
authors.forename: Nausheen
authors.initials: N
authors.lastname: Joondan
authors.affiliation: Department of Chemistry, Faculty of Science, University of Mauritius, Reduit, Mauritius. Electronic address: sabina@uom.ac.mu.
authors.forename: Sabina
authors.initials: S
authors.lastname: Jhaumeer-Laulloo
authors.affiliation: Department of Chemistry, Faculty of Science, University of Mauritius, Reduit, Mauritius.
authors.forename: Prakashanand
authors.initials: P
authors.lastname: Caumul
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000031:analogs & derivatives* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D004952:Esters / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D008566:Membranes / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D010649:Phenylalanine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D013501:Surface-Active Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004952:Esters; D013501:Surface-Active Agents; D015060:1,2-Dipalmitoylphosphatidylcholine; C081581:colfosceril palmitate; D014443:Tyrosine; D010649:Phenylalanine
keywords: Antibacterial activity; CMC; Cationic amino acid based surfactants; Minimum inhibitory concentration; Phospholipid