Abstract
Quaternary ammonium amphiphiles are a class of compounds with a wide range of commercial and industrial uses. In the pharmaceutical field, the most common quaternary ammonium surfactant is benzalkonium chloride (BAC), which is employed as a preservative in several topical formulations for ocular, skin, or nasal application. Despite the broad antimicrobial activity against Gram-positive and Gram-negative bacteria, as well as fungi and small enveloped viruses, safety concerns regarding its irritant and cytotoxic effect on epithelial cells still remain. In this work, quaternary ammonium derivatives of leucine esters (C10, C12 and C14) were synthesised as BAC analogues. These cationic surfactants were characterised in terms of critical micelle concentration (CMC, by tensiometry), cytotoxicity (MTS and LDH assays on the Caco-2 and Calu-3 cell lines) and antimicrobial activity on the bacterial species Staphylococcus aureus and Enterococcus faecalis among the Gram-positives, Escherichia coli and Pseudomonas aeruginosa among the Gram-negatives and the yeast Candida albicans. They showed satisfactory surface-active properties, and a cytotoxic effect that was dependent on the length of the hydrophobic chain. Lower minimum inhibiting concentration (MIC) values were calculated for C14-derivatives, which were comparable to those calculated for BAC toward Gram-positive bacteria and slightly higher for Gram-negative bacteria and C. albicans. Thus, the synthesised leucine-based quaternary ammonium cationic surfactants can potentially find application as promising surface-active compounds with antimicrobial activity.
Highlights
Amino-acid-based surfactants are a promising class of amphiphiles obtained by the condensation of an amino acid as a polar head and one or two acyl/alkyl chains as hydrophobic tails [1]
The formation of quaternary ammonium salts is an established strategy for obtaining antimicrobial compounds that has already been explored for other new classes of amphiphiles [13]
We synthesised and characterised the surface activity, cytotoxicity, and antimicrobial properties of two series of linear quaternary ammonium compounds, based on the amino acid leucine and methionine and with different hydrophobic chain lengths (C10, C12 and C14). These amphiphiles, especially derivatives with a C12 and C14 hydrocarbon chain, showed a satisfactory cytotoxicity and an antibacterial profile that was comparable to benzalkonium chloride (BAC), with higher activity observed against Gram-positive bacteria [14]
Summary
Amino-acid-based surfactants are a promising class of amphiphiles obtained by the condensation of an amino acid as a polar head and one or two acyl/alkyl chains as hydrophobic tails [1]. According to the site of the introduction of the hydrophobic tail on the amino acid functional groups (carboxylic or amine) and the charge of the amino acid side chain, anionic, cationic and zwitterionic amphiphiles can be obtained Both anionic and cationic amino-acid-based surfactants have been widely investigated and proposed in pharmaceutical and cosmetics formulations as alternatives to commercial surfactants due to their favourable physicochemical properties (e.g., foamability and emulsification) and toxicological profiles [4]. We synthesised and characterised the surface activity, cytotoxicity, and antimicrobial properties of two series of linear quaternary ammonium compounds, based on the amino acid leucine and methionine and with different hydrophobic chain lengths (C10, C12 and C14) These amphiphiles, especially derivatives with a C12 and C14 hydrocarbon chain, showed a satisfactory cytotoxicity and an antibacterial profile that was comparable to benzalkonium chloride (BAC), with higher activity observed against Gram-positive bacteria [14]. We investigated the surface properties, cytotoxicity and antimicrobial activity of these novel materials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
