CONICET | Buscador de Institutos y Recursos Humanos

Extracts rich in anthraquinones (AQs) of Heterophyllaea pustulata Hook. f. (Rubiaceae), have shown in vitro antifungal effect against planktonic microorganisms. We have established that their purified AQs exhibit photosensitizing activity type I and/or II. Since the most important group of opportunistic fungal pathogens are Candida species, in this study we evaluate the antifungal activity of Rubiadin 1-methyl ehter (RubME), one of the majority AQs from these extracts, against different Candida strains, analyzing whether this effect could be increased by irradiation. RubME was isolated from the benzenic extract of roots by several chromatographic methods; and identified by their spectral data (UV-V and RMN). Minimum Inhibitory Concentration (MIC) of RubME was determined by following the protocols of the Clinical and Laboratory Standards Institute, testing twelve concentrations (0.24 to 500 µg/mL) against two C. tropicalis strains (NCPF 3111 and clinical) and a C albicans strain (NCPF 3153). The assay was performed simultaneously under darkness and irradiation with an Actinic Phillips lamp. The RubME antifungal activity was compared with Amphotericin B, a synthetic antifungal agent. RubME decreased meaningfully the growth of all strains in darkness. Thus, the MICs were 250 µg/mL for clinical C. tropicalis, 31.3 µg/mL for C. tropicalis NCPF and 15.6 µg/mL for C. albicans NCPF. Under irradiation, this inhibition percentage was achieved at lower concentrations: being 31.3 µg/mL for the clinical strain, 15.6 µg/mL for C. tropicalis NCPF and 7.81 µg/mL for C. albicans NCPF. RubME exhibits a very good antifungal activity in vitro, which can be enhanced by light action, against several Candida species, mainly on C. albicans. Therefore, RubME could have application in photodynamic therapy for Candida infections.