ABSTRACT
The aim was to provide the insight into the biology of C. albicans influenced by undescribed yet properties of saponin-rich (80%-98%) fractions (SAPFs), isolated from extracts of Trifolium alexandrinum, T. incarnatum, T. resupinatum var. resupinatum aerial parts. Their concentrations below 0.5 mg/mL were arbitrarily considered as subMICs for C. albicans ATCC 10231 and were further used. SAPFs affected yeast enzymatic activity, lowered tolerance to the oxidative stress, to the osmotic stress and to the action of the cell wall disrupting agent. In their presence, germ tubes formation was significantly and irreversibly inhibited, as well as Candida invasive capacity. The evaluation of SAPFs interactions with anti-mycotics showed synergistic activity, mainly with azoles. Fluconazole MIC was lowered-susceptible C. albicans ATCC 10231 was more susceptible, and resistant C. glabrata (clinical strain) become more susceptible (eightfold). Moreover, the tested samples showed no hemolytic activity and at the concentrations up to 0.5 mg/mL did not reduce viability of fibroblasts L929. This study provided the original evidence that SAPFs of Trifolium spp. aerial part exhibit significant antimicrobial activity, by reduce the expression/quantity of important Candida virulence factors and have good potential for the development of novel antifungal products supporting classic drugs.
Subject(s)
Antifungal Agents , Candida albicans , Plant Components, Aerial/chemistry , Saponins , Trifolium/chemistry , Animals , Antifungal Agents/chemistry , Antifungal Agents/isolation & purification , Antifungal Agents/pharmacology , Azoles/agonists , Azoles/chemistry , Azoles/pharmacology , Candida albicans/growth & development , Candida albicans/pathogenicity , Cell Line , Cell Survival/drug effects , Drug Synergism , Fibroblasts/cytology , Fibroblasts/metabolism , Fluconazole/agonists , Fluconazole/chemistry , Fluconazole/pharmacology , Mice , Saponins/agonists , Saponins/chemistry , Saponins/isolation & purification , Saponins/pharmacologyABSTRACT
AIMS: To clarify the underlying synergistic antifungal mechanisms of retigeric acid B (RAB) in combination with azoles against Candida albicans. METHODS AND RESULTS: Increased accumulation of rhodamine 123 in C. albicans was measured by both spectrophotometric method and flow cytometry. The inhibitory properties to the drug efflux of C. albicans were determined spectrophotometrically. The decreased cellular ergosterol synthesis was measured using its unique spectrophotometric absorbance profile, and the downregulation expression levels of CDR1 and ERG11 were detected by real-time reverse transcription polymerase chain reaction. Transmission electron microscopy investigation found the wrinkled cell membrane and the impaired cell wall. CONCLUSIONS: RAB synergizes the antifungal effect of azoles against C. albicans by inhibiting efflux pump activity, targeting the ergosterol biosynthesis pathway and increasing the fluidity for the resulted ergosterol depletion. SIGNIFICANCE AND IMPACT OF THE STUDY: Investigating the mechanism of the synergy between RAB and azoles against C. albicans will help us to uncover the antifungal roles of this lichen-derived triterpene acid and find its possible clinical applications in overcoming fungal resistance.
