Enhancing the fungicidal activity of amphotericin B via vacuole disruption by benzyl isothiocyanate,a cruciferous plant constituent

Amphotericin B (AmB), a typical polyene macrolide antifungal agent, is widely used to treat systemic mycoses. In the present study, we show that the fungicidal activity of AmB was enhanced by benzyl isothiocyanate (BITC), a cruciferous plant-derived compound, in the budding yeast, Saccharomyces cerevisiae. In addition to forming a molecular complex with ergosterol present in fungal cell membranes to form K⁺-permeable ion channels, AmB has been recognized to mediate vacuolar membrane disruption resulting in lethal effects. BITC showed no effect on AmB-induced plasma membrane permeability; however, it amplified AmB-induced vacuolar membrane disruption in S. cerevisiae. Furthermore, the BITC-enhanced fungicidal effects of AmB significantly decreased cell viability due to the disruption of vacuoles in the pathogenic fungus Candida albicans. The application of the combinatorial antifungal effect of AmB and BITC may aid in dose reduction of AmB in clinical antifungal therapy and consequently decrease side effects in patients. These results also have significant implications for the development of vacuole-targeting chemotherapy against fungal infections.     

The fungicidal activity of novel nanoemulsion (X8W60PC) against clinically important yeast and filamentous fungi

Surfactant nanoemulsions are water in oil preparations that proved to have a broad spectrum biocidal activity against a variety of microorganisms including Gram-positive and Gram-negative bacteria, spores and enveloped viruses. These preparations are non-toxic to the skin, mucous membrane and gastrointestinal tissues at biocidal concentrations. In this study, 0.1% of the nanoemulsion designated X8W₆₀PC has shown fungicidal activity against yeast including Candida albicans and C. tropicalis in 15 minutes. C. tropicalis was more sensitive than C. albicans, which required a longer time or a higher concentration of the nanoemulsion to achieve killing. Neutral to slightly alkaline pH was more effective in killing the yeast cells than acidic pH. Using the minimum inhibitory concentration assay, 0.08% of the nanoemulsion was inhibitory to C. albicans, and parapsilosis and filamentous fungi including Microsporum gypseum,Trichophyton mentagrophytes,Trichophyton rubrum,Aspergillus fumigatus andFusarium oxysporum.None of the individual ingredients was as effective a fungicidal as the nanoemulsion at equivalent concentration. This shows that the nanoemulsion structure is an important factor in the anti-fungal activity. The X8W₆₀PC has great potential as a topical anti-fungal agent and further investigation into the mechanism of fungicidal action is warranted.This revised version was published online in October 2005 with corrections to the Cover Date.     

Antimicrobial activity of certain essential oils against hindgut symbionts of the drywood termite Kalotermes flavicollis Fabr. and prevalent fungi on termite-infested wood

Abstract:  When the kalotermitid Kalotermes flavicollis Fabr. pseudergates exposed to Casuarina wood wafers treated separately with different concentrations (5, 15 and 30  μ l/2 g wood wafer) of the essential oils, their spirochaete and flagellate populations abnormally reduced in numbers and vigour. The lophomonadids Joenia sp. and Mesojoenia sp. were the most adversely affected flagellates followed by the polymastigid Foaina sp. and the trichomonadid Tricercomitus sp. The Taxodium distichum essential oil evidently appeared to have the greatest adverse effect on the flagellates (95–100% decline in numbers within 2–4 days) followed by the Eucalyptus citriodora (89–100%) and the Cupressus sempervirens oils (31–100%). While with the hindgut spirochaetes, the adverse effect seemed to be reversed where the E. citriodora essential oil had the greatest effect (54–100%) followed by C. sempervirens (46–100%) and T. distichum (8–100%) oils. Moreover, the essential oils were assayed for their antifungal activity, at 15, 20, 25, 30, and 50  μ l/1 ml acetone/15 ml Czapek-Dox medium, against isolates of four woodrotting fungi associated with Casuarina timber, Aspergillus sp., Penicillium sp., Fusarium sp. and Mucor sp. by a method based on inhibition of the fungus growth on agar plates. E. citriodora exhibited the most potent fungicidal activity against the tested four fungi, followed by T. distichum oil. While the C. sempervirens essential oil appeared to have the least significant antifungal property.     

HP (2-20) derived from the amino terminal region of helicobacterpylori ribosomal protein L1 exerts its antifungal effects by damaging the plasma membranes of Candida albicans.

The fungicidal effects of the peptide HP (2-20). derived from the N-terminal sequence of Helicobacter pylori ribosomal protein L1 (RPL1). have been investigated. HP (2-20) displays a strong fungicidal activity against various fungi, without haemolytic activity against human erythrocyte cells, and the fungicidal activity is inhibited by Ca2+ and Mg2+ ions. In order to investigate the fungicidal mechanism(s) of HP (2-20). the amount of intracellular trehalose was measured in C. albicans. It was found that the amounts of intracellular trehalose were decreased when HP (2-20) was used. The action of the peptide against fungal cell membranes was further examined by the potassium-release test; HP (2-20) was found to increase the amount of K+ released from the cells. Furthermore, HP (2-20) caused significant morphological changes, as shown by scanning electron microscopy, and by testing the membrane disrupting activity using liposomes (phosphatidyl choline/cholesterol; 10: 1, w/w). Our results suggest that HP (2-20) may exert its antifungal activity by disrupting the structure of cell membranes, via pore formation or direct interaction with the lipid bilayers.     

Structural Optimization,Fungicidal Activities Evaluation,DFT Study and Structure-Activity Relationship of Dopamine Derivatives with Benzothiazole Fragment from Polyrhachis dives

In our previous work, two dopamine derivatives with benzothiazole fragment were isolated and identified from Polyrhachis dives (P. dives). Based on their characteristic structure, we used them as lead compound to carry out structural optimization and subsequent fungicidal evaluation. Here 20 dopamine derivatives with benzothiazole fragment were designed and synthesized by a facile method, and their structures were characterized by ¹H-NMR, ¹³CNMR and HMRS. In bioassays, most of the title compounds possess potential fungicidal activities against Altenaia alternala (A. alternala) and Botrytis cinerea (B. cinerea). Especially, (E)-N-(2-(benzo[d]thiazol-6-yl)ethyl)-3-(p-tolyl)acrylamide and (E)-N-(2-(benzo[d]thiazol-6-yl)ethyl)-3-(4-(trifluoromethyl)phenyl)acrylamide displayed 29.3 mg/L and 10.7 mg/L EC₅₀ value against A. alternala, respectively, which possessed equivalent fungicidal activities level to hymexazol.     

In vitro antifungal activities of voriconazole and reference agents as determined by NCCLS methods: Review of the literature

Voriconazole (Vfend™) is a new triazole that currently is undergoing phase III clinical trials. This review summarizes the published data obtained by NCCLS methods on the in vitro antifungal activity of voriconazole in comparison to itraconazole, amphotericin B, fluconazole, ketoconazole and flucytosine. Voriconazole had fungistatic activity against most yeasts and yeastlike species (minimum inhibitory concentrations [MICs] <2 μg/ml) that was similar or superior to those of fluconazole, amphotericin B, and itraconazole. Against Candida glabrata and C. krusei, voriconazole MIC ranges were 0.03 to 8 and 0.01 to >4 μg/ml, respectively. For four of the six Aspergillus spp. evaluated, voriconazole MICs (< 0.03 to 2 μg/ml) were lower than amphotericin B (0.25 to 4 μg/ml) and similar to itraconazole MICs. Voriconazole fungistatic activity against Fusarium spp. has been variable. Against F. oxysporum and solani, most studies showed MICs ranging from 0.25 to 8 μg/ml. Voriconazole had excellent fungistatic activity against five of the six species of dimorphic fungi evaluated (MIC₉₀s < 1.0 μg/ml). The exception was Sporothrix schenckii (MIC₉₀s and geometric mean MICs ≥ 8 μg/ml). Only amphotericin B had good fungistatic activity against the Zygomycetes species (voriconazole MICs ranged from 2 to >32 μg/ml). Voriconazole showed excellent in vitro activity (MICs < 0.03 to 1.0 μg/ml) against most of the 50 species of dematiaceous fungi tested, but the activity of all the agents was poor against most isolates of Scedosporium prolificans and Phaeoacremonium parasiticum (Phialophora parasitica). Voriconazole had fungicidal activity against most Aspergillus spp., B. dermatitidis, and some dematiaceous fungi. In vitro/in vivo correlations should aid in the interpretation of these results. This revised version was published online in June 2006 with corrections to the Cover Date.     

Physicochemical modification of the excretion product of Saccharomyces cerevisiae killer strains results in fungicidal activity against Candida albicans and Tricophyton mentagrophytes

It is known that certain yeast strains, so called 'killers', can produce and excrete proteinaceous toxins that can induce death of other sensitive strains. We obtained a stable fungicidal factor (SKF) through concentration and stabilization of the excretion product of certain killer strains of Saccharomyces cerevisiae (K1 and K2). The isolated proteinaceous complex exhibited activity at broad ranges of pH (4-7.5) and temperatures (20-37.5 degrees C). It was significantly lethal against Candida albicans and Tricophyton mentagrophytes. SKF showed stability and activity after storage, with a mean half-life of 6 months at 4 degrees C or at -20 degrees C.     

Fungicidal effect of hydrogen peroxide on fungal infection of rainbow trout eggs

Exposure to 1,500 μg/ml of hydrogen peroxide (H₂O₂) for 60 min at 13°C was found to be injurious to rainbow trout eggs. On the other hand, the concentration which effectively inhibited pathogenic fungi in vitro was substantially less than this toxic dosage; specifically, 500 μg/ml for 60 min at 20°C to inhibit the zoosporic stage and 1,000 μg/ml for 60 min at 20°C to inhibit the vegetative stage. From in vivo tests, treatment with 1,000 μg/ml of H₂O₂ for 60 min at 13°C was found to be the most effective procedure to control fungal infection and increase the hatching rate of rainbow trout eggs.     

Direct cell penetration of the antifungal peptide,MMGP1, in Candida albicans

An antifungal peptide, MMGP1, was recently identified from marine metagenome. The mechanism of cellular internalization of this peptide in Candida albicans was studied using fluorescein 5–isothiocynate (Sigma, California, USA) labeling followed by fluorescence microscopy and flow cytometry analyses. The peptide could enter C. albicans cells even at 4 °C, where all energy‐dependent transport mechanisms are blocked. In addition, the peptide internalization was not affected by the endocytic inhibitor, sodium azide. The kinetic study has shown that the peptide was initially localized on cell membrane and subsequently internalized into cytosol. The MMGP1 treatment exhibited time‐dependent cytotoxicity in C. albicans as evidenced by SYTOX Green (Molecular Probes Inc., Eugene, Oreg) uptake. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.