Resumo

Bacteria in biofilms contribute to chronicity of persistent infections such as those associated with implanted medical devices. The pressure for finding new antibacterial agents drives the search of active molecules from plants. In Brazilian Caantinga biome, located in northeast region, medicinal plants are an important social and cultural component. Based in ethnobotanical data and aiming to reproducing the mode of preparation of extracts by the local communities, this study focused to investigate 25 aqueous plant extracts against to well-known models of biofilm-forming bacteria: Staphylococcus epidermidis ATCC 35984 and Pseudomonas aeruginosa ATCC 27853. The screening (using 4 mg/mL) against S. epidermidis revealed that 7 extracts present an interesting antibiofilm activity (they allowed ≤ 60% of biofilm formation), while just 3 extracts were able to inhibit more than 50% of bacterial growth. Regarding P. aeruginosa, the extracts exhibited a different activity profile, inhibiting the bacterial growth more severely (4 extracts) than preventing biofilm development. For further investigation, we selected 3 extracts, which were capable to inhibit biofilm formation without involving bacterial death: leaves of Hn (PCA 02); fruits of Al (PCA 28) and fruits of Pp (PCA 55). The biofilm formation under action of these extracts were also analysed by Scanning Electron Microscopy using Permanox™. When compared with the untreated samples, all extracts showed a strong inhibition of biofilm formation structure, reducing the few adherent cell in small cluster or even single cells. The cytotoxicity of these extracts (4.0, 2.0 and 0.4 mg/ml) was examined against Vero cell line using the MTT assay. The PCA 02 extract showed no toxicity in all concentrations when compared with the untreated sample. However, the PCA 28 extract demonstrated cytotoxicity only at the higher concentration, and the PCA 55 extract decreased the cell viability in 4 mg/mL and 2 mg/mL. We performed a preliminary qualitative phytochemical screening with the three extracts. The TLC analysis showed the presence of flavonoids, terpenoids and amines. This study provides a scientific basis that may justify some ethnopharmacological use of these Caatinga plants, indicating plants with high potential for antibiofilm drugs and a limited cytotoxicity in vitro.