The use of plants or their parts as alternative therapies for disease is very common in many countries worldwide. Secondary metabolites present in the extracts of certain plants can inhibit or halt the development of certain pathogen species. The present study assessed the possible antimicrobial activities of a popular crude aqueous extract. The aerial parts of the Amazon tree Bellucia grossularioides (L) Triana (popularly known as Muúba or Angry-Jambo) were prepared according to folk recommendations and tested against four microorganisms related to health concerns in three concentrations (20, 10 and 5 mg/ml). The results showed no antimicrobial potential against Staphylococcus aureus, Candida albicans and Candida krusei, which cause furunculosis and leukorrhea, respectively. Additionally, growth inhibition of the toxigenic fungus Aspergillus parasiticus was assayed in vitro and the results showed no inhibitory activity for any of the tested concentrations. These findings contradict the traditional knowledge and may assist the targeting of future therapeutics practices. However, an inhibitory effect was observed for all forms of the preparations and concentrations tested on the roots of Allium cepa, indicating phytotoxic effects.