Reduction of Candida tropicalis biofilms by the photodynamic action of Rubiadin, a natural anthraquinone.

J. MARIONI, L.R. COMINI, J.L. CABRERA, M. G. PARAJE, S.C. NÚÑEZ MONTOYA.

Maresias

Encuentro; XII Encuentro Latinoamericano de Fotoquimica y Fotobiologia.; 2015

Enriched-anthraquinones (AQs) extracts of Heterophyllaea pustulata (Rubiaceae), have shown in vitro antifungal effect against Candida biofilms. Purified AQs from bioactive extracts exhibit photosensitizing activity. Antifungal activity of Rubiadin (RUB), a majority AQs from these extracts, was evaluated on Candida tropicalis biofilms, analyzing if this effect could be increased by irradiation and quantifying the reactive oxygen species (ROS) and reactive nitrogen intermediate.RUB, isolated from benzenic extract, was identified by their RMN data. Biofilm quantification was performed by the O´Toole & Kolter method on C. tropicalis NCPF 3111 and C. tropicalis clinical. RUB was tested at four concentrations in triplicate, under darkness and irradiation. The supernatant was used to measure the superoxide anion (O2?-) production by the Nitro-Blue Tetrazolium (NBT) reaction, and nitric oxide (NO) generation by Griess reagent. The total system antioxidant capability was determined by FRAP assay and the activation of SOD by NBT assay. Amphotericin B (AMP B) was used as control.RUB decreased the biofilms formation of both strains only under irradiation, being the reduction percentage (%R) on the clinical strain (82.1 ± 3.0 %) greater than the observed over reference strain (61.2 ± 4.8 %) at the same concentration (1.98 µg/mL); even RUB achieved a higher %R than AMP B (61.2 ± 4.8 % at CIM). The observed decrease in both biofilms was correlated with an increase in the production of O2?- and NO. Moreover, no activation of SOD was observed, but there was an increase in total antioxidant system.In conclusion, in vitro antifungal activity of RUB against biofilms of C. tropicalis is mediated by a photodynamic mechanism: O2?- production (Type I), together with the activation of the total antioxidant system that not allowed the complete biofilm elimination. Therefore, it would be promising evaluate the effect of consecutive periods of irradiation to achieve the biofilms eradication.