Potencial terapêutico do extrato metanólico de casca de açaí no controle antimicrobiano de Enterococcus faecalis

Abstract

Persistent endodontic infections associated with Enterococcus faecalis motivate the investigation of natural products with potential antimicrobial activity. This in vitro study evaluated methanolic açaí epicarp (fruit peel; Euterpe oleracea Mart.) extract using broth microdilution, 24-hour bacterial count monitoring, and a crystal violet adhesion assay. For the longitudinal assay, four independent experiments per concentration, three technical replicates and six time points were specified; available count data were evaluated with a linear mixed model containing a random intercept and first-order autoregressive structure. Concentration was treated as a factor, time was represented by linear and quadratic terms, and comparisons among concentrations at each time point were adjusted by Holm's method. No visual inhibition occurred at the tested concentrations, establishing an MIC greater than 20 mg/mL. In the mixed model, the overall concentration effect was not significant (p = 0.9936); the linear and quadratic time terms and the experiment effect were significant, whereas concentration-by-time interactions remained above 0.05. Adjusted comparisons identified lower estimated means for 1 mg/mL at some time points at the retained intermediate time points (4, 8, and 12 hours), with no differences among concentrations at 0, 2, and 24 hours. This isolated pattern did not constitute a dose-dependent response. In the crystal violet assay, factorial ANOVA indicated group, concentration, and interaction effects (p < 0.0001), which remained significant in an HC3 robust sensitivity analysis. At 20 mg/mL, mean absorbance in the test group was 1.75 units above the negative control. However, non-normality, variance heterogeneity, and especially extract pigmentation and precipitation precluded attribution of the increased signal to adhesion or bacterial biomass. Under the evaluated conditions, the crude extract did not demonstrate a concentration-dependent antimicrobial effect against E. faecalis. The results delimit the activity of the tested fraction and indicate the need for interference controls, other fruit fractions, and independent bacterial viability quantification methods.