Photodynamic action of 1-methyl ether rubiadin, a natural anthraquinone, over Candida tropicalis biofilms.

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

Córdoba

Congreso; XI Congreso Argentino de Microbiología General (SAMIGe) 2015 - Córdoba; 2015

Sociedad Argentina de Microbiología General

Rubadin 1-methyl ether (RME) is a anthraquinone (AQ) isolated from the bioactive extracts of aphototoxic shrub, Heterophyllaea pustulata Hook f. (Rubiaceae), which grows in northwestern ofArgentina. We have established that this AQ along with others present in the bioactive extracts of thisplant, exhibit photosensitizing properties. In this work, we assessed the in vitro antifungal activity ofRME over Candida tropicalis biofilms, under darkness and irradiation in order to establish whether thiseffect could be photoestimulated; we also quantified the production of reactive oxygen species (ROS)and reactive nitrogen intermediate (RNI) in the two evaluated experimental conditions.RME, purified from benzenic extract, was identified by their RMN data. Biofilm quantification of C.tropicalis NCPF 3111 and C. tropicalis clinical was performed by the O?Toole & Kolter method. RMEwas tested at three concentrations in triplicate, under darkness and irradiation. The supernatant wasused to measure O2·- production by the Nitro-Blue Tetrazolium (NBT) reaction, and RNI for nitricoxide (NO) generation by Griess reagent. The total system antioxidant capability was determined byFRAP assay and the activation of SOD by NBT assay. Amphotericin B (AMP B) was used asantifungic control.The biofilms formation of both strains was reduced by RME action only under irradiation. Thus, RMEachieved a percentage reduction (%R) of approximately 81.8 ± 2.6 % on the clinical strain biofilm atthe three tested concentrations, whereas on the biofilm of the reference strain only generated a 47 ±10 %R at a single concentration (15.6 μg/mL). In addition, RME was more active than AMP B (61.2 ±4.8 % at CIM). We noted that biofilms reduction is correlated with a large increase in the production ofO2·- and NO. Moreover, we observed an inactive SOD and an increase in total antioxidant system.In conclusion, we demonstrated that the in vitro antifungal activity of RME against biofilms of C.tropicalis is due to the photodynamic mechanism Type I, and the activation of the total antioxidantsystem not allowed the complete biofilm eradication. Therefore, it would be promising evaluate theeffect of consecutive periods of irradiation to eliminate the biofilms.