Atividade antimicrobiana e anti-inflamatória de produtos naturais sobre patógenos respiratórios

Abstract

Respiratory infections are leading causes of morbidity and mortality worldwide. The presence of a bacterial etiology generally leads to an intervention with antimicrobial therapy in these infections. Moreover, the abusive and indiscriminate use of antibiotics has produced bacterial resistance, which currently represents a serious public health problem. Thus, natural products may be new therapeutic options to combat drugresistant bacteria. Given the above, this study aimed to investigate the antimicrobial and anti-inflammatory of four plant species: Bixa orellana L. (annatto), Chenopodium ambrosioides L. (American wormseed), Mentha piperita L. (peppermint) and Psidium guajava L. (guava). From the hydroalcoholic extracts of B. orellana (seeds), C. ambrosioides (leaves), M. piperita (leaves) and P. guajava (leaves) in vitro antimicrobial activity was determined by agar diffusion assay, followed by the broth microdilution assay, against seven bacterial strains causing respiratory infections, including: Acinetobacter baumannii, Bordetella pertussis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes. The antimicrobial activity on biofilm formation was evaluated against reference strains of biofilm-producing P. aeruginosa and S. aureus. The most promising extracts were subjected to chemical characterization by high-performance liquid chromatography (HPLC), cytotoxicity, and anti-inflammatory activity test by evaluation of nitric oxide and hydrogen peroxide inhibition as well as their effects on phagocytosis in mice peritoneal macrophages. The tested plant extracts showed antimicrobial activity against at least one of the microorganisms tested. The B. orellana extract showed the highest inhibition zone (16 mm) against S. pyogenes, while the smaller one (8 mm) was found in M. piperita extract against B. pertussis and S. pyogenes. The broth microdilution method was more sensitive, it was demonstrated that extracts of B. orellana, M. piperita, and P. guajava showed activity against all tested pathogens. The lowest inhibitory concentration detected was 0.5 mg/ml P. guajava extract front bacteria P. aeruginosa and S. aureus. P. guajava and B. orellana extracts were able to reduce biofilm formation by P. aeruginosa in 95% and by S. aureus in 93%, both at a concentration of 64 mg/ml. Of the four plant extracts, the one from M. piperita was the most promising, since showed both antimicrobial activity against all the strains studied and the ability to reduce nitric oxide production in macrophages stimulated with LPS. The results indicate a potential of this plant species in the research and development of new antimicrobial agents against the major respiratory pathogens and their associated disease.