In vitro antimicrobial activity of methanolic extracts from cutaneous secretions of Amazonian amphibians against phytopathogens of agricultural interest

Abstract

The biochemical defense mechanisms of amphibians involve cutaneous secretions of bioactive molecules with antimicrobial activity. This study evaluated the in vitro activity of methanolic extracts from cutaneous secretions of two amphibian species of the Bufonidae family, Rhaebo guttatus and Rhinella marina, in the control of the phytopathogens Fusarium udum, Fusarium solani, Colletotrichum truncatum, Aspergillus flavus, Rhizoctonia solani, Macrophomina phaseolina, and Calonectria pseudometrosideri. The R. guttatus extract decreased the mycelial growth of F. udum, F. solani, A. flavus, and M. phaseolina at some tested concentrations. The R. marina extract decreased the mycelial growth of C. truncatum at the concentration of 0.5 mg mL-¹, and inhibited the mycelial growth of A. flavus at concentrations of 0.1 and 0.5 mg mL-¹, which was similar to the inhibition by the positive control. The R. marina extract also decreased the microsclerotia production by R. solani at concentrations of 0.2 and 0.3 mg mL-¹. In addition, the extracts inhibited conidial sporulation and germination at varying degrees. The inhibition of appressoria formation in C. truncatum by the R. guttatus and R. marina extracts was 85-99% and 63-100%, respectively. Our results demonstrated that treatment with extracts from R. guttatus and R. marina cutaneous secretions showed antifungal activity against the studied phytopathogens.

A crude methanolic extract from the parotoid gland secretion of Rhaebo guttatus stimulates the production of reactive species and pro‑inflammatory cytokines by peritoneal macrophages

“…In Brazil, the most extensively studied amphibian-derived skin secretions are from Rhinella marina (R. marina; Cururu toad), which contains compounds, such as marinobufagin, telecinobufagin, bufalin, marinobufotoxin, cholesterol, dehydrobufotenine, and suberoyl arginine (2,22,23). A variety of biological effects have been attributed to the compounds in R. marina skin secretions extracts, including cytotoxic, immunomodulatory, antifungal, antimutagenic, and anti-plasmodial activities (9)(10)(11)(22)(23)(24)(25).…”

“…In addition to R. marina, another common frog species in Brazil is R. guttatus, particularly in the Amazon Basin; however the compounds in their skin secretions are poorly characterized (2,5). Some compounds were identified, such as N-methyl-5-hidroxytryptamine, bufotenine, dehydrobufotenine, 3β,16 β-dihydroxybufa-8 (14),20,22-trienolide, marinobufagin, and bufatrienolides (2,7,8), and biological effects have been reported in the literature, including cytotoxic, anti-plasmodial, fungicidal, hemolytic and antimutagenic activities (8)(9)(10)(11).…”

“…Ferreira et al (8) demonstrated that extracts from the secretion of the parotoid gland of R. guttatus exhibit hemolytic and cytotoxic activity against tumor and non-tumor cells. Toxic activity against Plasmodium falciparum and phytopathogenic fungi has also been reported (9,10). Oliveira et al (11) observed that a methanolic extract from the parotoid gland secretion of R. guttatus exhibited both mutagenic and antimutagenic activities, indicating the need for further studies.…”

Investigation of crude methanolic extract from poison secreted by the Rhaebo gutattus on status redox antioxidant in mice

“…There are studies that have demonstrated the biological activity as the effects that extracts from the secretion of the parotoid gland of R. guttatus exhibit hemolytic and cytotoxic activity against tumor and non-tumor cells (Ferreira et al 2013); toxic activity against Plasmodium falciparum and phytopathogenic fungi (Banfi et al 2016;Raasch-Fernandes et al 2021); mutagenic and antimutagenic (Oliveira et al 2019); nociception properties (Mailho-Fontana et al 2014) and immunomodulatory activity (Pelissari et al 2023).…”