Chemical identification and evaluation of the antimicrobial activity of fixed oil extracted from Rhinella jimi.

Context: The toad Rhinella jimi (Stevaux, 2002) (Bufonidae) is used in traditional medicine to treat a number of illnesses (inflammation, infections, and wounds) in humans as well as animals.

Objectives: The present work examined the antimicrobial actions of the extracted oils from the body fat of R. jimi (ORJ) against fungi and standard and multi-resistant lines of bacteria, as well as their effects when combined with aminoglycosides.

Materials And Methods: The toads were collected in the municipality of Exu in Pernambuco State, Brazil, and their body fat oils extracted in a Soxhlet apparatus using hexane. A gas chromatograph coupled to a mass spectrometer was used to identify the fatty acids, based on their methyl esters. The antimicrobial activities of the oil were analyzed against standard and multi-resistant lines of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, as well as against fungal lines of Candida albicans and Candida krusei using the broth micro-dilution method.

Results: The minimum inhibitory concentrations (MIC) of ORJ were 512 µg/mL for Candida krusei and ≥1024 µg/mL for the other microorganisms. When associated with amikacin, ORJ demonstrated an increase in its ability to inhibit E. coli growth (from 156.25 to 39.06 µg/mL), indicating synergistic interaction. In the same way, when allied with amikacin, gentamicin, and neomycin, the ORJ reduced the MICs meaningly, against P. aeruginosa.

Conclusions: These data will enable searches to be made to obtain new products in combination with antibiotics, enhancing the efficacy of these drugs against drug-resistant microorganisms.