EFFECT OF USNIC ACID ON OXIDATIVE STRESS OF RESISTANT Candida albicans BIOFILMS

PERALTA MARIANA, DA SILVA MARÍA ÁNGEL, ORTEGA MARÍA GABRIELA, CABRERA JOSÉ LUIS, PARAJE MARÍA GABRIELA.

Córdoba

Congreso; Reunión Internacional de Ciencias Farmacéuticas ? RICiFa 2014.; 2014

Reunión Internacional de Ciencias Farmacéuticas ? RICiFa 2014.

EFFECT OF USNIC ACID ON OXIDATIVE STRESS OF RESISTANT Candida albicans BIOFILMS Key words: usnic acid, antifungal activity, Candida albicans, biofilms The continued emergence of infections with antifungal resistant Candida strains requires constant searching of new antifungal drugs. Thus, native flora is an important source of new chemical structures. Usnic acid (UA) [2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bH)-dibenzo-furandione] is a well-known compound obtained from lichen species of Usnea genus. No previous studies related to biofilms oxidative stress in UA presence have been reported. The aim of this work was to characterize the effects of UA on C.albicans biofilms by evaluating oxidative stress. Materials and methods Compound: UA was purified from benzene extract of the lichen. Spectroscopic data was coincident with those previously reported. Microorganisms: two strains of C.albicans isolated from the oral cavity were used, a sensitive strain (SCa) and an azole-resistant strain (RCa), which overexpresses transporter genes. Biofilm formation: was measured by adhesion to 96-well plate and crystal violet stain. Reactive oxygen species (ROS): was assayed by the reduction of the nitro-blue tetrazolium (NBT). Total superoxide dismutase (SOD) activity: was assayed based on the inhibition of NBT reduction. Total antioxidant capacity of biofilms: was assayed by FRAP method. Results UA at 4 µg/mL reduced both strains biofilms (86.50 and 82.58% of inhibition with respect to the control for RCa and SCa, respectively). In both biofilms treated with 4 µg/mL of UA, ROS measurements increased four-fold. SOD levels were higher (seven-fold) than basal ones. The basal levels of the total antioxidant capacity of biofilm were similar in both strains. However, SCa evidenced a considerable increase in FRAP in presence of UA. Conclusions C.albicans biofilms were reduced by UA, even in RCa. As expected for a sensitive strain, the more significant inhibition of biofilms was observed in SCa. There was an increase of ROS and antioxidant system in response to stress. These preliminary results encourage the study of mechanisms of action and combination assays with other antifungals.