title: Antimicrobial, antibiofilm and cytotoxic activities of Hakea sericea Schrader extracts.
abstract: BACKGROUND
  Hakea sericea Schrader is an invasive shrub in Portuguese forests.
  
  
  OBJECTIVE
  The goal of this work was to evaluate the antimicrobial activity of H. sericea extracts against several strains of microorganisms, including the ability to inhibit the formation of biofilms. Additionally the cytotoxic properties of these extracts, against human cells, were assessed.
  
  
  METHODS
  The antimicrobial activity of the methanolic extracts of H. sericea was assessed by disk diffusion assay and Minimum Inhibitory Concentration (MIC) value determination. The antibiofilm activity was determined by quantification of total biofilm biomass with crystal violet. Cytotoxicity was evaluated by hemolysis assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test.
  
  
  RESULTS
  For Gram-positive bacteria, MIC values of H. sericea methanolic extracts ranged between 0.040 and 0.625 mg/mL, whereas the fruits extract yielded the lowest MIC for several strains of microorganisms, namely, S. aureus, B. cereus, L. monocytogenes and clinical methicillin-resistant S. aureus (MRSA). Stems and fruits extract at 2.5 mg/mL effectively eradicated the biofilm of S. aureus ATCC 25923, SA 01/10 and MRSA 12/10. Regarding leaves extract, hemolysis was not observed, and in the case of stems and fruits, hemolysis was verified only for higher concentrations, suggesting its low toxicity. Fruits extract presented no toxic effect to normal human dermal fibroblasts (NHDF) cells however for concentrations of 0.017 and 0.008 mg/mL this extract was able to decrease human breast adenocarcinoma cells (MCF-7) viability in about 60%, as MTT test results had confirmed. This is a clearly demonstrator of the cytotoxicity of this extract against MCF-7 cells.
authors.affiliation: CICS-UBI - Health Sciences Research Centre, Faculty of Health Sciences, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
authors.forename: Angelo
authors.initials: A
authors.lastname: Luís
authors.affiliation: CICS-UBI - Health Sciences Research Centre, Faculty of Health Sciences, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
authors.forename: Luiza
authors.initials: L
authors.lastname: Breitenfeld
authors.affiliation: CICS-UBI - Health Sciences Research Centre, Faculty of Health Sciences, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
authors.forename: Susana
authors.initials: S
authors.lastname: Ferreira
authors.affiliation: CICS-UBI - Health Sciences Research Centre, Faculty of Health Sciences, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Duarte
authors.affiliation: CICS-UBI - Health Sciences Research Centre, Faculty of Health Sciences, University of Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Domingues
keywords: Antibiofilm; Antimicrobial; Cytotoxicity; Hakea sericea