Research of the antimicrobial activity of the poison from Rhinella icterica (Amphibia, Anura)

Abstract

Amphibians exhibit two types of cutaneous glands: mucous and granular. The secretion produced in their skin glands exhibit several chemical components. These substances have been studied regarding biological activity, showing aenesthetic, hallucinogen and antimicrobial effects, among others. Due to the diversity of Brazilian species, and considered that only few studies assessed this issue, the present study aim to investigate the antimicrobial activity of the poison produced by the parotoid macroglands of the toad Rhinella icterica originated from Rubião Júnior, Botucatu, São Paulo state. We assessed the effect of different poison concentrations on Escherichia coli e Staphylococcus aureus cultures, as well as the time required for antimicrobial action to perform. R. icterica poison presented weak antimicrobial activity for both bacteria considered, with a stronger effect on S. aureus. The poison acts in concentrations higher than 50 mg/mL, with a larger effectiveness at 100mg/mL. Time required for action was equal or superior than 30 minutes for S. aureus and superior than 15 minutes to E. coli. These data may support future studies involving the isolation of the substances confering antimicrobial activity to the poison of R. icterica, as well as the minimum concentrations required for the refered action.