Candida albicans is a fungal species commonly associated with biofilmformation in human diseases. The present study investigated the prooxidant and antioxidanteffects of 2′,4′-dihydroxy-5′-(1′′′,1′′′-dimethylallyl)-8-prenylpinocembrin (8PP), a naturalprenylflavonoid, on  C.albicans biofilms, by studying cellular stress and antioxidantresponse.

Biofilmsof azole-sensitive (SCa) andazole-resistant (RCa) C.albicans strains were treatedwith different concentrations of 8PP (1.5 µM to 1000 µM).  Biofilms were studied by crystal violet and confocalscanning laser microscopy (CSLM).  Analysisof biofilmstructures was performed by COMSTAT software.  Reactive OxygenSpecies (ROS) were detected by the reduction of NBT, and Reactive NitrogenIntermediates (RNI) by the Griess assay. ROS accumulation was also detected inside biofilmsby using 2′,7′-dichlorodihydrofluorescein diacetate probe and visualized byCSLM. Superoxidedismutase (SOD) activity and the total antioxidant capacity ofbiofilms were measured by spectrophotometric methods. This work remarks the oxidative stress achieved by 8PP at lower concentrations(25 µM to 100 µM); however, at higher concentrations (200 µM to 1000 µM) anantioxidant effect was observed, with increased antioxidant defenses. The mayorchanges in redox balance were observed in SCa biofilms, showing increased SODactivity values and the highest levels of nitrosative stress at 200µM of 8PP, comparedto non-treated controls and RCa biofilms. Analysescarried out by COMSTAT, showed that biofilms treated with higherconcentrations of 8PP showed differentdiffusion distances in their structures when were compared to controls. Thepresent study shows for the first time, a concentration-dependent dual prooxidant-antioxidant action of 8PP that can alter the biofilm formation.