The Antioxidant Peptide Salamandrin-I: First Bioactive Peptide Identified from Skin Secretion of Salamandra Genus (Salamandra salamandra)

Abstract

Amphibian skin is a multifunctional organ that plays key roles in defense, breathing, and water balance. In this study, skin secretion samples of the fire salamander (Salamandra salamandra) were separated using RP-HPLC and de novo sequenced using MALDI-TOF MS/MS. Next, we used an in silico platform to screen antioxidant molecules in the framework of density functional theory. One of the identified peptides, salamandrin-I, [M + H]+ = 1406.6 Da, was selected for solid-phase synthesis; it showed free radical scavenging activity against DPPH and ABTS radicals. Salamandrin-I did not show antimicrobial activity against Gram-positive and -negative bacteria. In vitro assays using human microglia and red blood cells showed that salamandrin-I has no cytotoxicity up to the concentration of 100 µM. In addition, in vivo toxicity tests on Galleria mellonella larvae resulted in no mortality at 20 and 40 mg/kg. Antioxidant peptides derived from natural sources are increasingly attracting interest. Among several applications, these peptides, such as salamandrin-I, can be used as templates in the design of novel antioxidant molecules that may contribute to devising strategies for more effective control of neurological disease.

Neuroprotective effects on microglia and insights into the structure–activity relationship of an antioxidant peptide isolated from Pelophylax perezi

“…This result suggests that these peptides might have similar antioxidant mechanisms. Note that the protonation at N ‐terminus increases the acceptor properties of salamandrin‐I 40 …”

“…Haemolysis percentage was calculated as: [(A(peptide)‐A(PBS)/(A(Triton X‐100) – A(PBS)] × 100. 18 , 38 , 39 , 40 …”

“…Despite the large variety of peptides already described in the biodiversity of European amphibians, 40 such as the antimicrobial brevinins 49 and esculentins, 50 no studies had been done with the skin secretion of P. perezi. From the HPLC analysis of the crude skin secretion, we identified more than 20 fractions, including that containing the peptide under investigation (Figure 1H).…”

The Arsenal of Bioactive Molecules in the Skin Secretion of Urodele Amphibians

“…This molecule was the first peptide identified in the skin of the European fire salamander (S. salamandra). The peptide neutralizes the free radicals DPPH and ABTS at nontoxic concentrations for microglial cells and human red blood cells (Plácido et al, 2020). The discovery of this peptide paves the way for further investigation of other antioxidant peptides in the skin secretion of urodeles.…”

The peptide secreted at the water to land transition in a model amphibian has antioxidant effects

“…CAFIs describe how the local electronic populations change when the number of the electrons of the system is modified, allowing the identification of sites that are prone to interact with nucleophiles (f + ), electrophiles (f − ) or free-radicals (f 0 ). These simple descriptors have been successfully employed for a variety of compounds with biological properties [31][32][33]. Hirshfeld's partition charge was employed to estimate the electronic populations to avoid negative indexes [34,35].…”