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cutaneous secretions of amphibians have bioactive compounds, such as peptides, with potential for biotechnological applications. therefore, this study aimed to determine the primary structure and investigate peptides obtained from the cutaneous secretions of the amphibian, Leptodactylus vastus, as a source of bioactive molecules. the peptides obtained possessed the amino acid sequences, GVVDiLKGAAKDLAGH and GVVDiLKGAAKDLAGHLASKV, with monoisotopic masses of [M + H] ± = 1563.8 Da and [M + H] ± = 2062.4 Da, respectively. The molecules were characterized as peptides of the class of ocellatins and were named as Ocellatin-K1(1-16) and Ocellatin-K1(1-21). Functional analysis revealed that Ocellatin-K1(1-16) and Ocellatin-K1(1-21) showed weak antibacterial activity. However, treatment of mice with these ocellatins reduced the nitrite and malondialdehyde content. Moreover, superoxide dismutase enzymatic activity and glutathione concentration were increased in the hippocampus of mice. In addition, Ocellatin-K1(1-16) and Ocellatin-K1(1-21) were effective in impairing lipopolysaccharide (LPS)-induced reactive oxygen species (ROS) formation and nf-kB activation in living microglia. We incubated hippocampal neurons with microglial conditioned media treated with LPS and LPS in the presence of Ocellatin-K1(1-16) and Ocellatin-K1(1-21) and observed that both peptides reduced the oxidative stress in hippocampal neurons. furthermore, these ocellatins demonstrated low cytotoxicity towards erythrocytes. these functional properties suggest possible to neuromodulatory therapeutic applications.The skin of amphibians has been the subject of interest and study of several research groups as well as pharmaceutical industries, due to the abundance and diversity of bioactive molecules with potential biotechnological applications, especially for the production of new drugs 1 . The characteristic way of living of amphibians is divided between aquatic and the terrestrial environment 2 . They possess a highly sensitive skin that is essential to its respiration and is highly vulnerable to environmental aggressions, such as desiccation, attack of microorganisms, ultraviolet radiation, and injuries 3 . This vulnerability has culminated in the development of an innate defense system as a survival strategy based on the expression, production, accumulation, and secretion of bioactive www.nature.com/scientificreports www.nature.com/scientificreports/ against E. coli with MIC of 125 μg/mL (Fig. 4) and inhibition percentage corresponding to 34.17 ± 11.66%. The optical density (630 nm) of E. coli decreased in a dose-dependent manner, showing significant reduction on viability for both the ocellatins at concentrations between 125 and 1000 μg/mL. The value 125 μg/mL of MIC is too high to be characterized as having significant antibacterial potential. Moreover, only Ocellatin-K1(1-16) showed any significant activity against S. aureus featuring MICs of 31.25 μg/mL and inhibition percentage corresponding to 30.79 ± 10.27%. This activity was not seen to be conc...

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In conclusion, PLS has a significant antidiarrheal effect in acute and secretory diarrhea. Further investigation is needed towards its use as a natural medicine to treat diarrhea.