OCCURENCE OF ANTIMICROBIAL ACTIVITY IN PAROTOID GLAND SECRETION OF THE TOAD Bufo ictericus

OLAH, D.(1), CASTRO, M.S.(1), FONTES, W.(2), SOUSA, M.V.(2), KYAW, C.(3), SCHWARTZ, E.F.(1)

(1)Laboratório de Toxinologia, (2)Laboratório de Bioquímica e Química de Proteínas, (3)Laboratório de Microbiologia, Universidade de Brasília, Brasília, DF, Brasil.

Amphibian skin secretions contain many active compounds which present a large diversity of biological activities, among them, antimicrobial activity. The aim of the present work was to identify antimicrobial compounds from parotoid gland secretion of the toad Bufo ictericus. Toad secretion was obtained by manual compression of the parotoid gland, and immediately lyophilized. The extract was ressuspended in 0,1% TFA/water (v/v) and applied into a Pharmacia C8 column. The elution was performed using a double linear gradient: TFA 0,1% / acetonitrile + 0,1% TFA. Fractions were collected manually, lyophilized, and rechromatographed using a Vydac C18 column. The antimicrobial activity of parotoid secretion and obtained fractions was assayed against Escherichia coli. Hemolytic activity was tested using human red blood cells. Molecular masses from active fractions were obtained by MALDI-TOF spectrometry. The parotoid secretion and five fractions presented antimicrobial activity. Only one of these fractions showed hemolytic activity. This chromatography procedure resulted in the isolation of fractions with molecular mass from 600 to 800kDa. The mass spectrometry data indicated that the antimicrobial activity of parotoid secretion of B. ictericus is not related to the presence of antimicrobial peptides, but probably to the presence of steroids, such as the bufadienolides. The chemical characterization of these antimicrobial compounds are in progress.

Support: DPP-UnB, PIBIC-CNPq 

CORRESPONDENCE TO:

E.N.F. SCHWARTZ, Laboratório de Toxinologia, Universidade de Brasília, Asa Norte, 70910-900, Brasília, DF, Brasil, Email: efschwa@unb.br