Trans-chalcone and quercetin down-regulate fatty acid synthase gene expression and reduce ergosterol content in the human pathogenic dermatophyte Trichophyton rubrum

Abstract

BackgroundFatty acid synthase (FAS) is a promising antifungal target due to its marked structural differences between fungal and mammalian cells. The aim of this study was to evaluate the antifungal activity of flavonoids described in the scientific literature as FAS inhibitors (quercetin, trans-chalcone, ellagic acid, luteolin, galangin, and genistein) against the dermatophyte Trichophyton rubrum and their effects on fatty acid and ergosterol synthesis.MethodsThe antifungal activity of the natural products was tested by the microdilution assay for determination of the minimum inhibitory concentration (MIC). The effect of the compounds on the cell membrane was evaluated using a protoplast regeneration assay. Ergosterol content was quantified by spectrophotometry. Inhibition of FAS by flavonoids was evaluated by an enzymatic assay to determine IC50 values. Quantitative RT-PCR was used to measure transcription levels of the FAS1 and ERG6 genes involved in fatty acid and ergosterol biosynthesis, respectively, during exposure of T. rubrum to the flavonoids tested.ResultsThe flavonoids quercetin and trans-chalcone were effective against T. rubrum, with MICs of 125 and 7.5 μg/mL for the wild-type strain (MYA3108) and of 63 and 1.9 μg/mL for the ABC transporter mutant strain (ΔTruMDR2), respectively. The MICs of the fluconazole and cerulenin controls were 63 and 125 μg/mL for the wild-type strain and 30 and 15 μg/mL for the mutant strain, respectively. Quercetin and trans-chalcone also reduced ergosterol content in the two strains, indicating that interference with fatty acid and ergosterol synthesis caused cell membrane disruption. The MIC of quercetin reduced the number of regenerated protoplasts by 30.26% (wild-type strain) and by 91.66% (mutant strain). Half the MIC (0.5 MIC) of quercetin did not reduce the number of regenerated wild-type fungal colonies, but caused a 36.19% reduction in the number of mutant strain protoplasts. In contrast, the MIC and 0.5 MIC of trans-chalcone and cerulenin drastically reduced protoplast regeneration in the two strains. The FAS1 gene was repressed in the presence of MICs of quercetin, trans-chalcone, fluconazole and cerulenin. The ERG6 gene was induced in the presence of MICs of fluconazole and cerulenin and was repressed in the presence of MICs of trans-chalcone and quercetin. Trans-chalcone and quercetin inhibited the enzymatic activity of FAS, with IC50 values of 68.23 and 17.1 μg/mL, respectively.ConclusionTrans-chalcone and quercetin showed antifungal activity against T. rubrum, reducing ergosterol levels and modulating the expression of FAS1 and ERG6.

Chalcone scaffolds as anti-infective agents: Structural and molecular target perspectives

“…Dermatophytosis are cutaneous mycosis caused by fungi of the family Arthrodermataceae (Dermatophytes), which are able to digest keratin and is the leading cause of fungal infection across the globe [180]. This is the most common fungal infection occur in human body.…”

Major challenges and perspectives in the diagnostics and treatment of dermatophyte infections

“…tomatoes, peppers), as well as legumes, tea and herbs. In addition, a specific group of flavonoids are chalcones considered to be interesting and promising compounds as precursors of new antifungal drugs due to their simple chemical structures allowing chemical synthesis in a safe and inexpensive way (Narender and Papi Reddy 2007;Nowakowska 2007;Bitencourt et al 2013). Other compounds are saponins, which are secondary metabolites found in the tissues of many plant species (Arif et al 2009).…”

HacA Governs Virulence Traits and Adaptive Stress Responses in Trichophyton rubrum

“…In regard to cell wall impairment, there was evidence that this effect correlated with defects in the cellular membrane composition, and potentially a link between impairment of membrane composition and a decrease in the protoplast regeneration ability (Bitencourt et al, 2013). Indeed, the deletion of hacA in T. rubrum affected the hyphae directionality, compromised protoplast regeneration, and enhanced its susceptibility to cell wall inhibitors.…”