Cationic Net Charge and Counter Ion Type as Antimicrobial Activity Determinant Factors of Short Lipopeptides

Abstract

To get a better insight into the antimicrobial potency of short cationic lipopeptides, 35 new entities were synthesized using solid phase peptide strategy. All newly obtained lipopeptides were designed to be positively charged from +1 to +4. This was achieved by introducing basic amino acid - lysine - into the lipopeptide structure and had a hydrophobic fatty acid chain attached. Lipopeptides were subjected to microbiological tests using reference strains of Gram-negative bacteria: Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Gram-positive bacteria: Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Enterococcus faecalis, and fungi: Candida albicans, Candida tropicalis, Aspergillus brasiliensis. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimal fungicidal concentration (MFC) were established for each strain. The toxicity toward human cells was determined by hemolysis tests via minimum hemolytic concentration (MHC) determination. The effect of the trifluoroacetic acid (TFA) counter ion on the antimicrobial activity of lipopeptides was also examined by its removing and performing the antimicrobial tests using counter ion-free compounds. The study shows that lipopeptides are more potent against Gram-positive than Gram-negative strains. It was revealed that positive charge equals at least +2 is a necessary condition to observe significant antimicrobial activity, but only when it is balanced with a proper length of hydrophobic fatty acid chain. The hemolytic activity of lipopeptides strongly depends on amino acid composition of the hydrophilic portion of the molecule as well as fatty acid chain length. Compounds endowed with a greater positive charge were more toxic to human erythrocytes. This should be considered during new lipopeptide molecules design. Our studies also revealed the TFA counter ion has no significant effect on the antimicrobial behavior of cationic lipopeptides.

Synthetic surfactin analogues have improved anti-PEDV properties

“…In a recent study of rigid amphipathic fusion inhibitors, compounds with deoxyribose or acetate as hydrophilic moieties had anti-HSV effects [22]. In addition, a recent study on antimicrobial activity of synthetic lipopeptides reported that lipopeptides with two to four positive charges and 16 carbon atoms in the lipid chain have potent antimicrobial activity [23]. Fatty acid chain length from 8 to 16 Synthetic surfactin analogues have improved anti-PEDV properties carbon atoms is positively correlated with antimicrobial activity, but is also positively correlated with hemolytic activity and membrane selectivity [24].…”

Ultrashort Cationic Lipopeptides–Effect of N-Terminal Amino Acid and Fatty Acid Type on Antimicrobial Activity and Hemolysis

“…In general, lipopeptides have dispersing, foaming, de-emulsificating, and moisturizing properties [1]. Furthermore, it is worth nothing that USCLs offer promising antimicrobial activities against planktonic cells and biofilms of bacteria and fungi [2][3][4][5]. USCLs were also applied to modify materials to prevent bacterial colonization crucial to hard-to-treat biomaterial-associated infections [6].…”

“…USCLs exhibit a detergent-like mode of action and hence their activity is based on disintegration of lipid bilayer. The main parameters considered to have substantial contribution to antimicrobial activity and toxicity of USCLs are the length of the fatty acid chain, net charge and the type of basic amino acids (usually arginine or lysine) [3,9,10]. According to the up-to-date epidemiological data resistance to commercially available lipopeptide drugs such as daptomycin, echinocandins, and polymyxins depends on a particular antibiotic, group of patients and geographical region; however it is still rare [11][12][13][14].…”

Characteristic of AMP and the effects of chemical modifications on the modulation of their antimicrobial properties

“…na zmianę rozpuszczalności w wodzie nowo zsyntezowanych związków, ich zdolności do samoorganizacji czy stabilności termicznej [49][50][51]. Mając to na uwadze zaprojektowano grupę polilizynowych lipopeptydów o krótkich sekwencjach potencjalnie wykazujących aktywność przeciwdrobnoustrojową wobec bakterii Gram-dodatnich (Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Enterococcus faecalis), Gram-ujemnych (Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa) i grzybów (Candida albicans, Candida tropicalis i Aspergillus brasiliensis) [52]. Zsyntezowane analogi różniły się długością łańcucha węglowego (od ośmiu do szesnastu atomów węgla) i wartością wypadkowego ładunku dodatniego.…”

“…Udowodniono, że koniugaty zawierające resztę kwasu palmitynowego (C 16 -KK-NH 2 , C 16 -KKK-NH 2 , C 16 -KKKK-NH 2 , C 16 -KGK-NH 2 , C 16 -KGKG-NH 2 ) oraz resztę kwasu mirystynowego (C 14 -KK-NH 2 , C 14 -KKK-NH 2 ) wykazywały najwyższą aktywność bakteriostatyczną oraz bakteriobójczą względem wszystkich sprawdzanych szczepów. Ponadto wykazano, że analog C 12 -KKKK-NH 2 jako jedyny z całej puli związków posiada aktywność przeciwgrzybiczą [52]. Aktywność lipopeptydów względem bakterii i grzybów zaobserwowano również w badaniach prowadzonych przez Armasa i współpracowników [53].…”