Lancehead pitvipers, Bothrops snakes, or, popularly, “jararacas”, are common and broadly distributed in the Americas, especially in Brazil, where they are responsible for causing a high number of snakebite accidents. Their venoms are able to induce local and systemic effects, such as hemorrhaging, acute kidney failure, and shock, that can be fatal. Among the compounds of the venom are phospholipases A₂ (PLA₂s), which are abundant in some Bothrops species. PLA₂s can perform different activities during envenoming, such as neurotoxicity, myotoxicity, and cytotoxicity, among others, through the hydrolysis of the ester bond at the sn-2 position of phospholipids, producing free fatty acids and lysophospholipids. Although different PLA₂s can be classified into different PLA₂ groups and subgroups, according to structure, function, size, localization and Ca²⁺ dependence, they converge to be available in biotechnological and therapeutic applications, such as antiviral and antitumor, among others, being relevant molecules to be deeply studied. Here, we provide the state of the art of PLA₂s, found in snake venoms, focusing on Bothrops venoms, as well as their potential applications, beyond their inhibitors, that also receive attention due their importance in PLA₂ studies and diverse applications.

Background/Objectives: Tuberculosis remains a major public health challenge due to the persistence of Mycobacterium tuberculosis (Mtb) and the emergence of multidrug-resistant strains. In this study, Pep-H, an HNP-1-derived antimicrobial peptide with the sequence RRYGTCIYQGRLWAF-NH₂, was used as a compact scaffold to examine how single-residue substitutions at the Cys position affected its biological and functional profile. Methods: A focused single-position substitution panel was generated by replacing Cys with Trp, Ala, Arg, or Met while preserving peptide length and sequence context, and the analogs were computationally prioritized according to their predicted antitubercular potential and contrasting side-chain properties. The peptides were synthesized, purified, characterized by HPLC and mass spectrometry, and evaluated for activity against Mtb H37Rv, cytotoxicity, hemolysis, ethidium bromide accumulation, and DPPH radical scavenging. Results: Pep-H retained the most favorable profile, showing the highest antimycobacterial potency, low hemolysis, favorable selectivity indices, enhanced ethidium bromide accumulation, and the strongest antioxidant response. All Cys substitutions reduced antimycobacterial activity, indicating that none of the tested residues reproduced the integrated biological profile of Pep-H. Conclusions: The contrasting outcomes of the Arg- and Met-containing analogs suggest that increased cationicity or sulfur retention alone was insufficient, while supporting a multifactorial contribution of Cys side-chain chemistry and the local GTCIY environment.

Antimicrobial peptides such as Melittin exhibit potent broad-spectrum activity but are limited by high cytotoxicity. The rational design of bioinspired Melittin-derived analogues represents a promising strategy to reduce toxicity while maintaining antimicrobial efficacy. In this study, Melittin and analogues (TT-1, FKW, and WKW) were synthesized using solid-phase peptide synthesis (SPPS) and characterized for biological and biophysical essays. Antimicrobial and hemolytic activity, serum stability, secondary structure, and membrane interaction were analysed. FKW and WKW exhibited broad-spectrum antimicrobial activity, with minimum inhibitory concentration (MIC) as low as 8 and 16 µg/mL against Staphylococcus aureus and Enterococcus faecium. Both analogues also showed improved activity against Klebsiella pneumoniae (32 µg/mL) and Pseudomonas aeruginosa (128 and 256 µg/mL for FKW and WKW, respectively) compared to Melittin (64 and 512 µg/mL). In terms of cytotoxicity, FKW and WKW showed significantly reduced hemolytic activity, with HC₅₀ values of 264.8 µg/mL and 237.2 µg/mL, respectively, resulting in improved selectivity indexes relative to Melittin (HC₅₀ of 7.9 µg/mL). In liposomes, both adopt α-helical structures and cause disruption via pore formation or detergent-like mechanisms. TT-1 showed minimal toxicity but weak antimicrobial activity (MIC > 256 µg/mL). Although FKW and WKW exhibited limited serum stability (half-lives of 2.2 and 1.5 h), their degradation may reduce systemic toxicity. Overall, these analogues demonstrate an improved balance between antimicrobial activity and safety.