Prospecção e otimização de peptídeos antimicrobianos de Nicotiana sp como alternativa aos antibióticos convencionais

Abstract

Bacterial resistance to conventional antibiotics is one of the main challenges facing public health, driving the search for new therapeutic strategies. In this context, antimicrobial peptides (AMPs) stand out as promising candidates due to their structural diversity and distinct mechanisms of action. Six natural peptides (Pep 1-6) previously identified in the floral nectar of a species of Nicotiana, extracted, purified by chromatographic techniques, and characterized by mass spectrometry, were evaluated for antibacterial activity against Staphylococcus aureus, S. epidermidis, Klebsiella pneumoniae, and Pseudomonas aeruginosa through inhibitory concentration assays. epidermidis, Klebsiella pneumoniae, and Pseudomonas aeruginosa using minimum inhibitory concentration (MIC) assays. Among them, only Pep6 (later named Nicotianin-I, NI) showed inhibitory activity and, although moderate, was selected as a model molecule for structural modifications by rational design. The modifications resulted in two bioinspired analogues, NI-A and NI-B, with significantly higher antibacterial activity than the precursor peptide. Mechanistically, NI-A showed greater membrane permeabilization, especially against S. epidermidis, while NI-B induced high production of reactive oxygen species in K. pneumoniae, associated with morphological damage. Both showed greater affinity for the bacterial membrane, attributed to the strengthening of electrostatic interactions. Structurally, NI-A and NI-B adopted an α-helix conformation in membrane-mimetic environments and remained disordered in aqueous media. In hemolysis assays, NI-A showed a concentration-dependent effect, while NI-B did not show significant hemolysis, indicating greater selectivity. Together, the results show that the rational modification of peptides derived from Nicotiana nectar made it possible to obtain analogues with greater antibacterial efficacy and differentiated toxicity profiles, reinforcing their potential as prototypes for the development of new therapies against resistant bacterial infections.