OCCURENCE OF ANTIMICROBIAL COMPOUNDS IN SKIN SECRETION OF THE TOAD Bufo rubescens

CUNHA FILHO, G.S.A.(1), CASTRO, M.S.(1), SOUSA, M.V.(2), FONTES, W.(2), SCHWARTZ, C.A.(1), SCHWARTZ, E.F.(1)

(1)Laboratório de Toxinologia, Universidade de Brasília, (2)Laboratório de Bioquímica e Química de Proteínas, Universidade de Brasília, Brasília, DF, Brasil.

INTRODUCTION. Antimicrobial peptides have been described in skin secretion of many amphibian species. These peptides act as compounds of the innate immunity in these animals. The objective of the present work was to identify and characterize antimicrobial agents from skin secretion of the toad Bufo rubescens. METODOLOGY. Toad skin secretion was obtained by electrical stimulation and the gland secretion by manual compression. These secretions were mixed, immediately lyophilized, dissolved in 0,1% (v/v) TFA/water, and applied into a Pharmacia C₈ column. The elution was performed using a double linear gradient. The fractions of interest were rechromatographed using a Vydac C₁₈ column.The molecular weights from individual peptide fractions were obtained by using MALDI-TOF mass spectrometer. The antimicrobial activity was assayed against Escherichia coli. Hemolytic activity was assayed using human red blood cells. RESULTS. The crude extract and two fractions from B. rubescens secretion showed inhibition against E. coli. These active fractions resulted on compounds of 1,369, 1,526, 684, 700 and 714 Da. None peptide fraction had significative hemolytic activity. CONCLUSION. This work showed the occurrence of antimicrobial compounds of low molecular weights in the skin secretion of Bufo rubescens.

Financial support: DPP, UnB.

CORRESPONDENCE TO:

CUNHA FILHO, G.S.A., Laboratório de Toxinologia, Universidade de Brasília, Brasília, 70910-900, DF, Brasil, Email: gcfilho@unb.br