Abstract

Several investigations have demonstrated in vitro antibacterial activity of plant extracts. Kalanchoe pinnata is globally used in folk medicine for the treatment of various diseases, such as diarrhea, infections, tuberculosis and fever. Among the enteropathogenic bacteria, enteroaggregative Escherichia coli (EAEC) is an important cause of diarrhea in the world. EAEC is also capable of forming biofilms, conformation that provides antibiotic resistance and a high degree of dispersion and reinfection, which may represent up to 80% of causes of human microbial infections. Thus, it becomes necessary to search for new antimicrobial agents with activity against biofilms. The aim of this study was to evaluate the cytotoxic, antibacterial and antibiofilm in EAEC from aqueous extracts of leaves and the flavonoids quercetin and rutin, occurring in K. pinnata. Leaf aqueous extracts were obtained and evaluated phytochemically. The cytotoxic activity was evaluated in human carcinoma cell lines HEp-2, Caco-2 and T84. The antibacterial activity was evaluated by the macrodilution method and the evaluation of antibiofilm activity was performed in Escherichia coli enteroaggregative (EAEC 042). Aqueous extracts of K pinnata do not show toxicity to Hep-2, but all other cell lines were sensitive to this extract. Instead, the flavonoids quercetin and rutin showed no cytotoxicity with any of the tested cell lines. Quercetin is capable of inhibiting bacterial growth of all tested strains. The aqueous leaf extract and quercetin were able to inhibit EAEC 042 biofilm formation above 50%. The results indicate the potential use of the species in treatment of bacterial infections.

Key words: Antimicrobials, EAEC 042, biofilms, quercetin, Crassulaceae.