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Quaternary Ammonium Leucine-Based Surfactants: The Effect of a Benzyl Group on Physicochemical Properties and Antimicrobial Activity

1
School of Pharmacy, University of Camerino, 62032 Camerino, Italy
2
School of Biosciences and Veterinary Medicine, University of Camerino, 62032 Camerino, Italy
3
School of Cancer and Pharmaceutical Sciences, Faculty of Life Sciences and Medicine, King’s College London, London SE1 9NH, UK
*
Author to whom correspondence should be addressed.
Pharmaceutics 2019, 11(6), 287; https://doi.org/10.3390/pharmaceutics11060287
Received: 21 May 2019 / Revised: 6 June 2019 / Accepted: 15 June 2019 / Published: 19 June 2019
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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. View Full-Text
Keywords: cationic surfactants; amino acid; surface tension; antibacterial activity; toxicological studies cationic surfactants; amino acid; surface tension; antibacterial activity; toxicological studies
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Perinelli, D.R.; Petrelli, D.; Vitali, L.A.; Bonacucina, G.; Cespi, M.; Vllasaliu, D.; Giorgioni, G.; Palmieri, G.F. Quaternary Ammonium Leucine-Based Surfactants: The Effect of a Benzyl Group on Physicochemical Properties and Antimicrobial Activity. Pharmaceutics 2019, 11, 287.

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