Antimicrobial Compounds from Skin Secretions of Species That Belong to the Bufonidae Family

Abstract

Skin secretions of toads are a complex mixture of molecules. The substances secreted comprise more than 80 different compounds that show diverse pharmacological activities. The compounds secreted through skin pores and parotid glands are of particular interest because they help toads to endure in habitats full of pathogenic microbes, i.e., bacteria, fungi, viruses, and protozoa, due to their content of components such as bufadienolides, alkaloids, and antimicrobial peptides. We carried out an extensive literature review of relevant articles published until November 2022 in ACS Publications, Google Scholar, PubMed, and ScienceDirect. It was centered on research addressing the biological characterization of the compounds identified in the species of genera Atelopus, Bufo, Duttaphrynus, Melanophryniscus, Peltopryne, Phrynoidis, Rhaebo, and Rhinella, with antibacterial, antifungal, antiviral, and antiparasitic activities; as well as studies performed with analogous compounds and skin secretions of toads that also showed these activities. This review shows that the compounds in the secretions of toads could be candidates for new drugs to treat infectious diseases or be used to develop new molecules with better properties from existing ones. Some compounds in this review showed activity against microorganisms of medical interest such as Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Coronavirus varieties, HIV, Trypanosoma cruzi, Leishmania chagasi, Plasmodium falciparum, and against different kinds of fungi that affect plants of economic interest.

Keywords: antifungal; antimicrobial peptides; antiprotozoal; antiviral; family Bufonidae; skin secretion.

Figure 1

Chemical structure of molecules with antimicrobial activity found in toads’ skin secretions. The first 19 structures belong to the group of bufadienolides, and the last one is an alkaloid.

Figure 2

Secondary structure of antimicrobial peptides found in toads. These peptides adopt an alpha helical conformation. They are rich in lysine residues (represented in blue) and the first amino acids interacting with bacterial membranes. Component names are in bold.