Troponoids Can Inhibit Growth of the Human Fungal Pathogen Cryptococcus neoformans. 2017

Maureen J Donlin, and Anthony Zunica, and Ashlyn Lipnicky, and Aswin K Garimallaprabhakaran, and Alex J Berkowitz, and Alexandre Grigoryan, and Marvin J Meyers, and John E Tavis, and Ryan P Murelli
Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA donlinmj@slu.edu.

Cryptococcus neoformans is a pathogen that is common in immunosuppressed patients. It can be treated with amphotericin B and fluconazole, but the mortality rate remains 15 to 30%. Thus, novel and more effective anticryptococcal therapies are needed. The troponoids are based on natural products isolated from western red cedar, and have a broad range of antimicrobial activities. Extracts of western red cedar inhibit the growth of several fungal species, but neither western red cedar extracts nor troponoid derivatives have been tested against C. neoformans We screened 56 troponoids for their ability to inhibit C. neoformans growth and to assess whether they may be attractive candidates for development into anticryptococcal drugs. We determined MICs at which the compounds inhibited 80% of cryptococcal growth relative to vehicle-treated controls and identified 12 compounds with MICs ranging from 0.2 to 15 μM. We screened compounds with MICs of ≤20 μM for cytotoxicity in liver hepatoma cells. Fifty percent cytotoxicity values (CC50s) ranged from 4 to >100 μM. The therapeutic indexes (TI, CC50/MIC) for most of the troponoids were fairly low, with most being <8. However, two compounds had TI values that were >8, including a tropone with a TI of >300. These tropones are fungicidal and are not antagonistic when used in combination with fluconazole or amphotericin B. Inhibition by these two tropones remains unchanged under conditions favoring cryptococcal capsule formation. These data support the hypothesis that troponoids may be a productive scaffold for the development of novel anticryptococcal therapies.

UI MeSH Term Description Entries
D008826 Microbial Sensitivity Tests Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses). Bacterial Sensitivity Tests,Drug Sensitivity Assay, Microbial,Minimum Inhibitory Concentration,Antibacterial Susceptibility Breakpoint Determination,Antibiogram,Antimicrobial Susceptibility Breakpoint Determination,Bacterial Sensitivity Test,Breakpoint Determination, Antibacterial Susceptibility,Breakpoint Determination, Antimicrobial Susceptibility,Fungal Drug Sensitivity Tests,Fungus Drug Sensitivity Tests,Sensitivity Test, Bacterial,Sensitivity Tests, Bacterial,Test, Bacterial Sensitivity,Tests, Bacterial Sensitivity,Viral Drug Sensitivity Tests,Virus Drug Sensitivity Tests,Antibiograms,Concentration, Minimum Inhibitory,Concentrations, Minimum Inhibitory,Inhibitory Concentration, Minimum,Inhibitory Concentrations, Minimum,Microbial Sensitivity Test,Minimum Inhibitory Concentrations,Sensitivity Test, Microbial,Sensitivity Tests, Microbial,Test, Microbial Sensitivity,Tests, Microbial Sensitivity
D003455 Cryptococcus neoformans A species of the fungus CRYPTOCOCCUS. Its teleomorph is Filobasidiella neoformans. Blastomyces neoformans,Debaryomyces neoformans,Filobasidiella neoformans,Lipomyces neoformans,Saccharomyces neoformans,Torula neoformans,Torulopsis neoformans,Cryptococcus neoformans var. grubii
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000666 Amphotericin B Macrolide antifungal antibiotic produced by Streptomyces nodosus obtained from soil of the Orinoco river region of Venezuela. Amphocil,Amphotericin,Amphotericin B Cholesterol Dispersion,Amphotericin B Colloidal Dispersion,Fungizone
D000935 Antifungal Agents Substances that destroy fungi by suppressing their ability to grow or reproduce. They differ from FUNGICIDES, INDUSTRIAL because they defend against fungi present in human or animal tissues. Anti-Fungal Agents,Antifungal Agent,Fungicides, Therapeutic,Antibiotics, Antifungal,Therapeutic Fungicides,Agent, Antifungal,Anti Fungal Agents,Antifungal Antibiotics
D014334 Tropolone A seven-membered aromatic ring compound. It is structurally related to a number of naturally occurring antifungal compounds (ANTIFUNGAL AGENTS).
D015725 Fluconazole Triazole antifungal agent that is used to treat oropharyngeal CANDIDIASIS and cryptococcal MENINGITIS in AIDS. Apo-Fluconazole,Béagyne,Diflucan,Fluc Hexal,FlucoLich,Flucobeta,Fluconazol AL,Fluconazol AbZ,Fluconazol Stada,Fluconazol von ct,Fluconazol-Isis,Fluconazol-ratiopharm,Flunazul,Fungata,Lavisa,Loitin,Neofomiral,Oxifungol,Solacap,Triflucan,UK-49858,Zonal,Apo Fluconazole,Fluconazol Isis,Fluconazol ratiopharm,UK 49858,UK49858

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