B1CTcu5 analogs as promising antimicrobial peptides, replacing the sequence cysteine

The development of new drugs has decreased considerably compared to previous years, and for this, it is necessary to prioritize obtaining new promising molecules with the ability to eradicate bacteria that cause emergency diseases, as indicated by the WHO. The peptide B1CTcu5 from Indian frog Clinotarsus curtipe belongs to the Brevinin-1 family and it has already been shown that it has potential activity against infectious bacteria. However, sequences that present cysteine in their structure present spontaneous reactions due to the presence of thiol groups, so it is difficult to know the exact sequence that show the activity. The aim of this research was to synthesize homologues of the B1CTcu5 peptide, and to evaluate its antimicrobial activity against ATCC strains as an initial phase. The peptides were obtained by solid phase synthesis using the Fmoc protection protocol, for all peptides were using Rink-amide resin and cleavage was performed with trifluoroacetic acid (95%), triisopropylsilane (2.5%), and water (2.5%). The peptides were purified and characterized by high-performance liquid chromatography and mass spectrometry. The antimicrobial activity was tested in Salmonella Typhi, Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. The characterization results confirmed the obtainment and purity of the peptides (> 95%) and showed minimal inhibitory concentration values between 15.6 - 62.5 µg/mol. These results show that the B1CTcu5 analogs could possess an effective antimicrobial activity using variations and replacing the sequence cysteine.