[Show abstract][Hide abstract] ABSTRACT: Enhanced control of species of Cryptococcus, non-fermentative yeast pathogens, was achieved by chemosensitization through co-application of certain compounds with a conventional antimicrobial drug. The species of Cryptococcus tested showed higher sensitivity to mitochondrial respiratory chain (MRC) inhibition compared to species of Candida. This higher sensitivity results from the inability of Cryptococcus to generate cellular energy through fermentation. To heighten disruption of cellular MRC, octyl gallate (OG) or 2,3-dihydroxybenzaldehyde (2,3-DHBA), phenolic compounds inhibiting mitochondrial functions, were selected as chemosensitizers to pyraclostrobin (PCS; an inhibitor of complex III of MRC). The cryptococci were more susceptible to the chemosensitization (i.e., PCS + OG or 2,3-DHBA) than the Candida with all Cryptococcus strains tested being sensitive to this chemosensitization. Alternatively, only few of the Candida strains showed sensitivity. OG possessed higher chemosensitizing potency than 2,3-DHBA, where the concentration of OG required with the drug to achieve chemosensitizing synergism was much lower than that required of 2,3-DHBA. Bioassays with gene deletion mutants of the model yeast Saccharomyces cerevisiae showed that OG or 2,3-DHBA affect different cellular targets. These assays revealed mitochondrial superoxide dismutase or glutathione homeostasis plays a relatively greater role in fungal tolerance to 2,3-DHBA or OG, respectively. These findings show that application of chemosensitizing compounds that augment MRC debilitation is a promising strategy to antifungal control against yeast pathogens.
[Show abstract][Hide abstract] ABSTRACT: K.L.C.); firstname.lastname@example.org (N.M.); email@example.com (Y.K.K.); firstname.lastname@example.org (B.C.C.) Abstract: Natural compounds that pose no significant medical or environmental side effects are potential sources of antifungal agents, either in their nascent form or as structural backbones for more effective derivatives. Kojic acid (KA) is one such compound. It is a natural by-product of fungal fermentation commonly employed by food and cosmetic industries. We show that KA greatly lowers minimum inhibitory (MIC) or fungicidal (MFC) concentrations of commercial medicinal and agricultural antifungal agents, amphotericin B (AMB) and strobilurin, respectively, against pathogenic yeasts and filamentous fungi. Assays using two mitogen-activated protein kinase (MAPK) mutants, i.e., sakA∆, mpkC∆, of Aspergillus fumigatus, an agent for human invasive aspergillosis, with hydrogen peroxide (H 2 O 2) or AMB indicate such chemosensitizing activity of KA is most conceivably through disruption of fungal antioxidation systems. KA could be developed as a chemosensitizer to enhance efficacy of certain conventional antifungal drugs or fungicides.
International Journal of Molecular Sciences 12/2012; 13(12):13867-13880. · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In addition to the fungal cellular membrane, the cellular antioxidant system can also be a viable target in the antifungal action of amphotericin B (AMB). Co-application of certain redox-potent natural compounds with AMB actually increases efficacy of the drug through chemosensitization. Some redox-potent chemosensitizers and AMB perturb common cellular targets, resulting in synergistic inhibition of fungal growth. Chemosensitizing activities of four redox-potent benzaldehydes were tested against clinical and reference strains of Candida albicans, C. krusei, C. tropicalis, and Cryptococcus neoformans in combination with AMB, based on assays outlined by the European Committee on Antimicrobial Susceptibility Testing. Two dihydroxybenzaldehydes (DHBAs), i.e., 2,3-DHBA and 2,5-DHBA, significantly enhanced activity of AMB against most strains, as measured by lower minimum inhibitory concentrations and/or minimum fungicidal concentrations (MFCs). A non-hydroxylated benzaldehyde, trans-cinnamaldehyde, showed chemosensitizing activity through lower MFCs, only. Contrastingly, a methoxylated benzaldehyde (3,5-dimethoxybenzaldehyde) had no chemosensitizing activity, as all strains were hypertolerant to this compound. Bioassays using deletion mutants of the model yeast, Saccharomyces cerevisiae, indicated DHBAs exerted their chemosensitizing activity by targeting mitochondrial superoxide dismutase. This targeting, in turn, disrupted the ability of the yeast strains to respond to AMB-induced oxidative stress. These in vitro results indicate that certain DHBAs are potent chemosensitizing agents to AMB through co-disruption of the oxidative stress response capacity of yeasts. Such redox-potent compounds show promise for enhancing AMB-based antifungal therapy for candidiasis and cryptococcosis.
Frontiers in Microbiology 01/2012; 3:261. · 3.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The cellular antioxidant system is a target in the antifungal action of amphotericin B (AMB) and itraconazole (ITZ), in filamentous fungi. The sakAΔ mutant of Aspergillus fumigatus, a mitogen-activated protein kinase (MAPK) gene deletion mutant in the antioxidant system, was found to be more sensitive to AMB or ITZ than other A. fumigatus strains, a wild type and a mpkCΔ mutant (a MAPK gene deletion mutant in the polyalcohol sugar utilization system). Complete fungal kill (≥99.9%) by ITZ or AMB was also achieved by much lower dosages for the sakAΔ mutant than for the other strains. It appears msnA, an Aspergillus ortholog to Saccharomyces cerevisiaeMSN2 (encoding a stress-responsive C(2)H(2)-type zinc-finger regulator) and sakA and/or mpkC (upstream MAPKs) are in the same stress response network under tert-butyl hydroperoxide (t-BuOOH)-, hydrogen peroxide (H(2)O(2))- or AMB-triggered toxicity. Of note is that ITZ-sensitive yeast pathogens were also sensitive to t-BuOOH, showing a connection between ITZ sensitivity and antioxidant capacity of fungi. Enhanced antifungal activity of AMB or ITZ was achieved when these drugs were co-applied with redox-potent natural compounds, 2,3-dihydroxybenzaldehyde, thymol or salicylaldehyde, as chemosensitizing agents. We concluded that redox-potent compounds, which target the antioxidant system in fungi, possess a chemosensitizing capacity to enhance efficacy of conventional drugs.
Frontiers in Microbiology 01/2012; 3:88. · 3.94 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Determine whether certain, natural phenolic compounds enhance activity of commercial antifungal drugs against yeast strains of Candida and Cryptococcus neoformans.
Twelve natural phenolics were examined for fungicidal activity against nine reference strains of Candida and one of C. neoformans. Six compounds were selected for synergistic enhancement of antifungal drugs, amphotericin B (AMB), fluconazole (FLU) and itraconazole (ITR). Matrix assays of phenolic and drug combinations conducted against one reference strain, each, of Candida albicans and C. neoformans showed cinnamic and benzoic acids, thymol, and 2,3- and 2,5-dihydroxybenzaldehydes (-DBA) had synergistic interactions depending upon drug and yeast strain. 2,5-DBA was synergistic with almost all drug and strain combinations. Thymol was synergistic with all drugs against Ca. albicans and with AMB in C. neoformans. Combinations of benzoic acid or thymol with ITR showed highest synergistic activity. Of 36 combinations of natural product and drug tested, none were antagonistic.
Relatively nontoxic natural products can synergistically enhance antifungal drug activity, in vitro.
This is a proof-of-concept, having clinical implications. Natural chemosensitizing agents could lower dosages needed for effective chemotherapy of invasive mycoses. Further studies against clinical yeast strains and use of animal models are warranted.
Letters in Applied Microbiology 02/2011; 52(5):506-13. · 1.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A male patient from Guinea-Bissau was admitted to Egas Moniz Hospital, Lisbon, complaining of fever and exhibiting a productive cough with mucopurulent discharge and weight loss. He had been using empirical medication with dexamethasone to treat his generalized facial swelling. At admission, he was cachectic and presented with soft facial edema, oropharyngeal thrush, and two fistulas of the palate. Acid-fast bacilli were detected in the sputum and were later identified as Mycobacterium tuberculosis. Cultures of the palatine exudate and biopsy resulted in the growth of Candida albicans. The patient was administered antituberculosis drugs and fluconazole, but his clinical situation deteriorated progressively. Extensive investigation of his clinical condition did not result in a conclusive diagnosis until he began to experience respiratory distress and subcutaneous nodules appeared on his face. Biopsies of the hypopharynx and nodules revealed the presence of Conidiobolus coronatus. After initiating combined antifungal and antibiotic therapy, the patient's clinical condition improved significantly. We report an unusual presentation of entomophthoromycosis and describe the clinical difficulties that delayed this diagnosis.
Medical mycology: official publication of the International Society for Human and Animal Mycology 12/2010; 48(8):1099-104. · 2.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: We report here a simple entry into naphtho[2,3-d]isoxazole-4,9-dione system containing a EWG in position 3 using the readily available 2,3-dichloro-1,4-naphthoquinone and nitromethyl derivatives in the presence of base. Antifungal activity of synthesised naphthoquinones was evaluated against ATCC and PYCC reference strains of Candida. The results suggest that the naphtho[2,3-d]isoxazole-4,9-dione scaffold has the potential to be developed into novel and safe therapeutic antifungal agents.