title: Antifungal activity of a prenylated flavonoid from Dalea elegans against Candida albicans biofilms.
abstract: BACKGROUND
  The continuing emergence of infections with antifungal resistant Candida strains requires a constant search for new antifungal drugs, with the plant kingdom being an important source of chemical structures.
  
  
  OBJECTIVE
  The present study investigated the antifungal effect of 2',4'-dihydroxy-5'-(1''',1'''-dimethylallyl)-8-prenylpinocembrin (8PP, formerly 6PP), a natural prenylflavonoid, on Candida albicans biofilms, and compared this with an azole antifungal (fluconazole) by studying the cellular stress and antioxidant response.
  
  
  METHODS
  The fluconazole sensitive (SCa) and azole-resistant (RCa) C. albicans strains were used, with biofilm formation being studied using crystal violet (CV) and confocal scanning laser microscopy (CSLM). The minimal inhibitory concentration for sessile cells (SMIC) was defined as the concentration of antifungal that caused a 50% (SMIC 50) and 80% (SMIC 80) reduction of treated biofilms. The reactive oxygen species (ROS) were detected by the reduction of nitro blue tetrazolium (NBT), and reactive nitrogen intermediates (RNI) were determined by the Griess assay. The activities of the superoxide dismutase (SOD) and catalase (CAT) antioxidant enzymes and the total antioxidant capacity of the biofilms were measured by spectrophotometric methods. ROS accumulation was also detected inside biofilms by using the fluorogenic dye 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA), which was visualized by CSLM.
  
  
  RESULTS
  The SCa and RCa biofilms were strongly inhibited by 8PP at 100 µM (SMIC 80). We observed that cellular stress affected biofilms growth, resulting in an increase of ROS and also of reactive nitrogen intermediates (RNI), with SOD and CAT being increased significantly in the presence of 8PP. The basal level of the biofilm total antioxidant capacity was higher in RCa than SCa. Moreover, in SCa, the total antioxidant capacity rose considerably in the presence of both 8PP and fluconazole.
  
  
  CONCLUSIONS
  Our data suggest that 8PP may be useful for the treatment of biofilm-related Candida infections, through an accumulation of endogenous ROS and RNI that can induce an adaptive response based on a coordinated increase in antioxidant defenses. 8PP may also have a therapeutic potential in C. albicans infections.
authors.affiliation: Departamento de Farmacia, Facultad de Ciencias Químicas, Instituto Multidisciplinario de Biología Vegetal (IMBIV) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, 5000 Córdoba, Argentina.
authors.forename: Mariana Andrea
authors.initials: MA
authors.lastname: Peralta
authors.affiliation: Facultad de Ciencias Exactas Físicas y Naturales, Instituto Multidisciplinario de Biología Vegetal (IMBIV) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Cátedra de Microbiología, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 299, Córdoba, Argentina.
authors.forename: María Angel
authors.initials: MA
authors.lastname: da Silva
authors.affiliation: Departamento de Farmacia, Facultad de Ciencias Químicas, Instituto Multidisciplinario de Biología Vegetal (IMBIV) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, 5000 Córdoba, Argentina.
authors.forename: María Gabriela
authors.initials: MG
authors.lastname: Ortega
authors.affiliation: Departamento de Farmacia, Facultad de Ciencias Químicas, Instituto Multidisciplinario de Biología Vegetal (IMBIV) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, 5000 Córdoba, Argentina.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Cabrera
authors.affiliation: Facultad de Ciencias Exactas Físicas y Naturales, Instituto Multidisciplinario de Biología Vegetal (IMBIV) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Cátedra de Microbiología, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 299, Córdoba, Argentina. Electronic address: paraje@efn.uncor.edu.
authors.forename: María Gabriela
authors.initials: MG
authors.lastname: Paraje
mesh_terms: D000935:Antifungal Agents / Q000302:isolation & purification / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002176:Candida albicans / Q000187:drug effects*; D025141:Drug Resistance, Fungal; D007887:Fabaceae / Q000737:chemistry*; D044950:Flavanones / Q000302:isolation & purification / Q000494:pharmacology; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology*; D015725:Fluconazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D018517:Plant Roots / Q000737:chemistry
chemical_list: C528861:2',4'-dihydroxy-5'-(1'''-dimethylallyl)-6-prenylpinocembrin; D000935:Antifungal Agents; D044950:Flavanones; D005419:Flavonoids; D015725:Fluconazole
keywords: Antioxidant defence system; Biofilms; Candida albicans; Dalea elegans; Oxidative stress; Prenylated flavonoid