Antifungal Activities of N-Arylbenzenesulfonamides against Phytopathogens and Control Efficacy on Wheat Leaf Rust and Cabbage Club Root Diseases

A set of N-arylbenzenesulfonamides with various substituents at the arylamine and benzenesulfonyl positions were prepared, and their antifungal properties were measured in vitro against such plant pathogenic fungi as Pythium ultimum, Phytophthora capsici, Rhizoctonia solani, and Botrytis cinerea. Compounds 3, 4, 8, 9, 10, 14, 16, 18, 20, 21, 24 and 27 had antifungal activity over a broad spectrum of the phytopathogenic fungi tested, where 50% of inhibition (ED₅₀) was in the range of 3-15 μg/ml. Based on the in vitro activity, six derivatives (3, 4, 10, 18, 21 and 27) were selected and tested further for their fungicidal efficacy in vivo. The fungicidal efficacy of 10, 21 and 27 had a disease control value of over 85% at 50 μg/ml against wheat leaf rust, while that of 4 was selective against cabbage club root disease.     

Antifungal pharmacodynamic characteristics of amphotericin B against Trichosporon asahii, using time-kill methodology

We determined the MIC of amphotericin B against 45 Trichosporon asahii isolates from various clinical and environmental sources, and used in vitro time-kill methods to characterize the relationship between amphotericin B concentrations and MIC for four representative T. asahii isolates. Amphotericin B had concentration-dependent antifungal activity. MICs ranged from 0.5 to 16 microg/ml, and most T. asahii isolates (76%, 34/45) were inhibited at safely achievable amphotericin B serum concentrations (< or = 2 microg/ml). However, 40% (18/45) of isolates were not killed at these concentrations (MFCs from 1.0 to 32 microg/ml). At concentrations > or = 2 x MIC, amphotericin B exhibited fungicidal activity (< 99.9% reduction in CFU) over a 12-hr time-period; the maximal effect was achieved at > or =4 x MIC. Susceptibility testing confirmed the resistance of T. asahii to amphotericin B, and in vitro pharmacodynamic results also suggest that amphotericin B is not suitable therapy for T. asahii infection.     

Controlled release of water-soluble polymeric complexes of sorbic acid with antifungal activities

We synthesized six water-soluble polymeric complexes of sorbic acid with polyvinylpyrrolidone of different molecular weight (mol wt). As shown by infrared absorption spectrum analysis, the complexes were formed by hydrogen bonding. The complexes (SC1, with mol wt=10 kDa, SC2 with mol wt=25 kDa, SC3 with mol wt=30 kDa, SC4 with mol wt=40 kDa, SC5 with mol wt=90 kDa, and SC6 with mol wt=360 kDa) were characterized as low mol wt (SC1, SC2, and SC3) and high mol wt (SC4, SC5, and SC6). The antifungal potencies of the complexes were tested by the macrodilution susceptibility method against environmental and clinically important fungi. Sorbic acid as well as the complexes exhibited minimum inhibitory concentrations (MICs) lower than potassium sorbate against all the strains tested. MICs of SC1, SC2, and SC3 were shown to be 2- to 4-fold lower for yeast and 1.5- to 3-fold lower than those of sorbic acid for moulds, respectively. The MICs of SC4 and SC5 against both of the Candida species tested ranged from 500 to 800 microg/ml, whereas for SC6 and sorbic acid they were about 1 mg/ml. The potencies of the high mol wt complexes against moulds were decreased by increasing the mol wt. For both of the moulds tested, the MICs of SC4 were slightly lower than those of sorbate. The MICs of sorbic acid and SC5 were equal to 300 microg/ml and 500 microg/ml respectively for Aspergillus parasiticus and for Penicillum viridicatum. The susceptibility to SC6 of all of the hyphomycetes tested was higher than that to sorbic acid. The low mol wt complexes and the sorbic acid exhibited minimal fungicidal concentrations (MFCs) 2 and 3 times higher respectively than the MICs. Sorbic acid and SC3 at a concentration of 2.5 mg/ml in an in vitro time kill curve study of Candida tropicalis were shown to be fungistatic, whereas SC1 and SC2 were fungicidal at the same concentrations. For Aspergillus parasiticus sorbic acid at 2.5 mg/ml was fungistatic for a 24-h period, whereas SC1, SC2, and SC3 were fungicidal.     

Antifungal activity against plant pathogenic fungi of chaetoviridins isolated from Chaetomium globosum

The Chaetomium globosum strain F0142, which was isolated from barnyard grass, showed potent disease control efficacy against rice blast (Magnaporthe grisea) and wheat leaf rust (Puccinia recondita). Two antifungal substances were purified from broth from this organism and identified as chaetoviridins A and B. Chaetoviridin A exhibited higher antifungal activity than chaetoviridin B against plant pathogenic fungi both in vitro and in vivo. Treatment with chaetoviridin A at 62.5 microg/mL suppressed the development of rice blast and wheat leaf rust by over 80%. The molecule also exhibited moderate control of tomato late blight, resulting in 50% control following the application of 125 microg/mL chaetoviridin A.     

Antifungal activity of a novel compound from Burkholderia cepacia against plant pathogenic fungi

AIMS: To investigate antifungal activity of a novel compound (named as CF66I provisionally) against plant pathogenic fungi, mainly including Fusarium sp., Colletotrichum lindemuthianum, Rhizoctonia solani, etc. METHODS AND RESULTS: Minimal inhibition concentrations (MIC) and minimal fungicidal concentrations (MFC) of CF66I for each fungi were determined using serial broth dilution method. The data demonstrated MIC ranged from 2.5 to 20.0 microg ml(-1) and MFC were shown at levels of < or =7.5 microg ml(-1) except Fusarium sp. With reverse microscopy, profound morphological alterations of fungal cells were observed after exposure to CF66I. Conidiospores were completely inhibited, and protoplasm aggregated to form chalamydospores because of the changes of cell permeability. Some chalamydospores were broken, suggesting the compound probably possessed strong ability of damaging the cell wall. In addition, CF66I was investigated for its antifungal stability against Curvularia lunata. The results showed CF66I kept strong fungi-static activity over-wide pH range (pH 4-9) and temperature range (from -70 to 120 degrees C). CONCLUSIONS: The compound CF66I exhibited strong and stable broad-spectrum antifungal activity, and had a significant fungicidal effect on fungal cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Results from prebiocontrol evaluations performed to date are probably useful in the search for alternative approaches to controlling serious plant pathogens.     

Evaluation of<Emphasis Type="Italic">in Vitro</Emphasis> antifungal activity of<Emphasis Type="Italic">N</Emphasis>-Benzylsalicylamide derivatives

A series of 65 derivatives of N-benzylsalicylamide was tested against eight potentially human pathogenic fungi by microdilution broth method modified according to M27-A standard. The majority of these compounds showed only weak in vitro antifungal activity. The most significant effect was observed against filamentous fungi Trichophyton mentagrophytes, Absidia corymbifera, and Aspergillus fumigatus while yeasts, in general, were less susceptible. N-(4'-Chlorobenzyl) salicylamides, N-(3',4'-dichlorobenzyl)-salicylamides, and partially N-benzylsalicylamides exhibited relatively high in vitro antifungal activity. The most efficient derivatives had MIC < or = 7.8 mumol/L against T. mentagrophytes. Regression analysis suggested an indirect relationship between MIC values and lipophilicity (log P).     

In vitro susceptibilities of Candida spp. to Panomycocin, a novel exo-beta-1,3-glucanase isolated from Pichia anomala NCYC 434

Panomycocin, the killer toxin of Pichia anomala NCYC 434 (K5), is a 49 kDa monomeric glycoprotein with exo-beta-1,3-glucanase activity (patent pending). In this study we evaluated the in vitro activity of panomycocin against a panel of 109 human isolates of seven different pathogenic Candida spp. using microdilution and time-kill methods. Panomycocin was most active against C. tropicalis, C. pseudotropicalis and C. glabrata with MIC(90) values of 1 microg/ml. It displayed significant activity against C. albicans and C. parapsilosis with MIC(90) values of 4 and 2 microg/ml, respectively. For C. krusei, the MIC(90) value was 8 microg/ml. Panomycocin was fungicidal against all the tested Candida spp. The MFC values were only one or 2 dilutions higher than the MICs with the exception of C. krusei isolates with MFCs greater than or equal to 4xMIC. Results of this study indicated that panomycocin could be considered as a natural antifungal agent against Candida infections and has significant potential for further investigation.     

In vitro activities of voriconazole, fluconazole, itraconazole and amphotericin B against non Candida albicans yeast isolates

Antifungal susceptibility testing was performed on 197 yeast isolates from the BCCM/IHEM biomedical fungi and yeasts collection (Belgian Co-ordinated Collections of Micro-organisms / IPH-Mycology) to study the in vitro activity of voriconazole against fluconazole, itraconazole and amphotericin B. MICs of the four antifungal agents were determined by an adapted NCCLS M27-A microdilution reference method. MIC readings were visually and spectrophotometrically determined. Optical density data were used for calculation of the MIC endpoints. For amphotericin B, the MIC endpoint was defined as the minimal antifungal concentration that exerts 90% inhibition, compared to the control growth. The azoles endpoints were determined at 50% inhibition of growth. The MIC distribution of voriconazole susceptibilities showed that 193 isolates had a MIC < or = 2 microg/ml and 185 a MIC < or = 1 microg/ml. Cross-tabulation of voriconazole, fluconazole, and itraconazole MICs indicated that voriconazole MICs raised with fluconazole and itraconazole MICs. The in vitro data obtained in this study suggest that voriconazole may also be effective treating yeast infection in patients infected with fluconazole or itraconazole resistant isolates.     

In vitro antifungal activities of anidulafungin and micafungin, licensed agents and the investigational triazole posaconazole as determined by NCCLS methods for 12,052 fungal isolates: review of the literature

The echinocandins anidulafungin and micafungin and the triazole posaconazole are currently undergoing phase III clinical trials. Caspofungin and voriconazole have recently been licensed for the treatment of aspergillosis (both agents), other less common mould (voriconazole) and candidal (caspofungin) infections. This review summarizes the published in vitro data obtained by NCCLS or NCCLS modified methods on the in vitro fungistatic and fungicidal activities of these five agents for yeasts and moulds in comparison to the established agents, amphotericin B, fluconazole, itraconazole, and flucytosine. Among the yeasts, the echinocandins have less activity for Candida parapsilosis and Candida guilliermondii, no activity for Cryptococcus neoformans and Trichosporon spp., but good fungistatic and fungicidal activity in vivo and in vitro for most of the other Candida spp.; this fungicidal activity has been reported by minimum fungicidal concentrations (MFCs) or time kill curve results. The new triazoles exhibit good fungistatic activity (but not fungicidal) for most Candida spp., C. neoformans, and Trichosporon spp. For the Aspergillus spp. evaluated, the echinocandins have similar or better fungistatic activity than those of amphotericin B and the triazoles, but fungicidal activity has been demonstrated only with amphotericin B and the triazoles, with the exception of fluconazole. Most studies showed posaconazole and voriconazole minimum inhibitory concentrations (MICs) ranging from 0.25 to 8 microg/ml for non-solani Fusarium spp., while MIC and minimum effective concentration (MEC) endpoints of the echinocandins were >8 microg/ml. The fungistatic activity of the triazoles is also superior to that of the echinocandins for most of the dimorphic fungi and the Zygomycetes. However, micafungin has activity for the mould phase of most dimorphic fungi, but not for the parasitic or yeast phase of Paracoccidioides brasiliensis. The echinocandins appear to have variable and species dependent fungistatic activity for the dematiaceous fungi, but all agents have poor or no activity against most isolates of Scedosporium prolificans. Only amphotericin B exhibit good fungistatic activity against the Zygomycetes. The combination of caspofungin with some triazoles, amphotericin B or liposomal amphotericin B has been synergistic in vitro, in animal models and in patients. Breakpoints are not available for any mould and antifungal agent combination. In vitro/in vivo correlations should aid in the interpretation of these results, but standard testing conditions are needed for the echinocandins, especially for mould testing, to obtain reliable results.     

Kinetics and requirements for activation of macrophages for fungicidal activity: effect of protein synthesis inhibitors and immunosuppressants on activation and fungicidal mechanism.

Peritoneal-and pulmonary macrophages can be activated in vitro with lymphokines (LK) or IFN-gamma, without exogenous lipopolysaccharide, for fungicidal activity against several pathogenic fungi. However, neither the biochemical nor metabolic events of the activation process or of the effector phase have been defined. In the present work we sought to elucidate these events with time-course studies using inhibitors of protein synthesis as well as immunosuppressive agents. We found that protein synthesis inhibitors abrogated the activation process, because cycloheximide (CHX) (1-2 micrograms/ml) prevented activation of macrophages for fungicidal activity against Candida albicans, Blastomyces dermatitidis, and Paracoccidioides brasiliensis. Blocking of the activation process by CHX was not due to macrophage cytotoxicity, and CHX did not impair the ability of nonactivated macrophages to kill Candida parapsilosis. In kinetic studies we showed that activation of macrophages was induced in 4 hr of LK treatment and that CHX had no effect if added after this time. In contrast to CHX, therapeutic concentrations of hydrocortisone (HC), such as less than or equal to 5 micrograms/ml, or cyclosporin A (CsA), 5 micrograms/ml, did not significantly inhibit LK activation of macrophages for killing of fungi. In the effector phase, the fungicidal capacity of activated macrophages in short-term (less than or equal to 4 hr) killing assays could not be abrogated by CHX (5 micrograms/ml), HC (100 micrograms/ml), or CsA (10 micrograms/ml). These results demonstrate that the activation but not the effector mechanism of macrophages for fungicidal activity is blocked by inhibition of protein synthesis. In contrast, therapeutic concentrations of HC or CsA may not interfere with activation of macrophages or their killing mechanisms, thus providing a rationale for antifungal immunotherapy in certain clinical situations (e.g., infection in the immunosuppressed patient).     

Activity of some aminoglycoside antibiotics against true fungi, Phytophthora and Pythium species

AIMS: To investigate the in vitro antifungal and antioomycete activities of some aminoglycosides against true fungi and Phytophthora and Pythium species and to evaluate the potential of the antibiotics against Phytophthora late blight on plants. METHODS AND RESULTS: Antifungal and antioomycete activities of aminoglycoside antibiotics (neomycin, paromomycin, ribostamycin and streptomycin) and a paromomycin-producing strain (Streptomyces sp. AMG-P1) against Phytophthora and Pythium species and 10 common fungi were measured in potato dextrose broth (PDB) and on seedlings in pots. Paromomycin was the most active against Phytophthora and Pythium species with a minimal inhibitory concentration of 1-10 microg ml(-1) in PDB, but displayed low to moderate activities towards other common fungi at the same concentration. Paromomycin also showed potent in vivo activity against red pepper and tomato late blight diseases with 80 and 99% control value, respectively, at 100 microg ml(-1). In addition, culture broth of Streptomyces sp. AMG-P1 as a paromomycin producer exhibited high in vivo activity against late blight at 500 microg freeze-dried weight per millilitre. CONCLUSIONS: Among tested aminoglycoside antibiotics, paromomycin was the most active against oomycetes both in vitro and in vivo. SIGNIFICANCE AND IMPACT OF THE STUDY: Data from this study show that aminoglycoside antibiotics have in vitro and in vivo activities against oomycetes, suggesting that Streptomyces sp. AMG-P1 may be used as a biocontrol agent against oomycete diseases.     

Two novel antifungal peptides distinct with a five-disulfide motif from the bark of Eucommia ulmoides Oliv

Two antifungal peptides, named EAFP1 and EAFP2, have been purified from the bark of Eucommia ulmoides Oliv. Each of the sequences consists of 41 residues with a N-terminal blockage by pyroglutamic acid determined by automated Edman degradation in combination with the tandem mass spectroscopy and the C-terminal ladder sequencing analysis. The primary structurs all contain 10 cysteines, which are cross-linked to form five disulfide bridges with a pairing pattern (C1-C5, C2-C9, C3-C6, C4-C7, C8-C10). This is the first finding of a plant antifungal peptide with a five-disulfide motif. EAFP1 and EAFP2 show characteristics of hevein domain and exhibit chitin-binding properties similar to the previously identified hevein-like peptides. They exhibit relatively broad spectra of antifungal activities against eight pathogenic fungi from cotton, wheat, potato, tomato and tobacco. The inhibition activity of EAFP1 and EAFP2 can be effective on both chitin-containing and chitin-free fungi. The values of IC(50) range from 35 to 155 microg/ml for EAFP1 and 18 to 109 microg/ml for EAFP2. Their antifungal effects are strongly antagonized by calcium ions.     

Bioactive saponins from Astragalus suberi L. growing in Yemen

From the aerial parts of Astragalus suberi L., Fabaceae, seven saponins were isolated. Based on spectral data (IR, 1H and 13C NMR and HR-FABMS), the structures were established as 3-O-(beta-D-glucopyranosyl)-soyasapogenol B (1); 3-O-(beta-D-glucuronopyranosyl)-soyasapogenol B (2); 3-O-[beta-D-galactopyranosyl (1-->2)-beta-D-glucopyranosyl]-soyasapogenol B (3); 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-galactopyranosyl (1-->2)-beta-D-glucopyranosyl]-soyasapogenol B (4); 3-O-[beta-L-rhamnopyranosyl (1-->2)-beta-D-galactopyranosyl (1-->2)-beta-D-glucopyranosyl]-11-hydroxy-soyasapogenol B (5); 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-galactopyranosyl (1-->2)-beta-D-glucuronopyranosyl]-soyasapogenol B (6) and 3-O-[alpha-L-rhamnopyranosyl (1-->2)-beta-D-galactopyranosyl (1-->2)-beta-D-glucuronopyranosyl]-complogenin (7). The isolated saponins exhibited antibacterial activities against Gram-positive and Gram-negative bacteria with minimum inhibitory concentration values >100 microg/ml, antifungal activity against all the strains tested with minimum fungicidal concentration values between 25 and 50 microg/ml and inhibited the growth of Hep-2 (human carcinoma of larynx), with IC50 values between 50 microg/ml (compounds 5-7) and 100 microg/ml (compounds 1-4), and Hela (human carcinoma of cervix) cell lines in culture with different IC50 values [74 (compound 7), 98 (compound 5) and 180 microg/ml (compounds 1-4 and 6)].     

Antifungal activity of essential oil and its constituents from Calocedrus macrolepis var. formosana Florin leaf against plant pathogenic fungi

Resistance to conventional fungicides causes the poor disease control of agriculture. Natural products from plants have great potential as novel fungicide sources for controlling pathogenic fungi. In this study antipathogenic activity of the leaf essential oil and its constituents from Calocedrus macrolepis var. formosana Florin were evaluated in vitro against six plant pathogenic fungi. Chemical analysis of leaf oil by GC/MS allowed identification of alpha-pinene (44.2%), limonene (21.6%), beta-myrcene (8.9%), beta-caryophyllene (8.2%), caryophyllene oxide (2.4%), alpha-cadinol (1.6%), beta-pinene (1.2%), and T-muurolol (1.1%) as main components. Sesquiterpenoid components of the oil were more effective than monoterpenoid components of the oil. In particular, T-muurolol and alpha-cadinol strongly inhibited the growth of Rhizoctonia solani and Fusarium oxysporum, with the IC(50) values < 50 microg ml(-1). These compounds also efficiently inhibited the mycelial growths of Colletotrichum gloeosporioides, P. funerea, Ganoderma australe and F. solani. These results showed that T-muurolol and alpha-cadinol possess antifungal activities against a broad spectrum of tested plant pathogenic fungi and could be used as potential antifungal agents for the control of fungal diseases in plants.     

Antifungal susceptibility of epigallocatechin 3-O-gallate (EGCg) on clinical isolates of pathogenic yeasts

This is the first report to investigate the antifungal susceptibility of 21 clinical isolates of seven Candida species to epigallocatechin 3-O-gallate (EGCg) and to compare with six antifungal agents, amphotericin B (AMPH), fluconazole (FLCZ), flucytosin (5FC), itraconazole (ITCZ), micafungin (MCFG), and miconazole (MCZ), using a method following the National Committee for Clinical Laboratory Standards (NCCLS) M27-A guidelines. Among the tested species, Candida glabrata exhibited the highest susceptibility to EGCg (MIC50, 0.5-1 microg/ml and MIC90, 1-2 microg/ml) compared favorably with FLCZ, although they were slightly less susceptible than to AMPH, 5FC, MCFG, ITCZ, and MCZ. Candida guilliemondii and Candida parapsilosis (MIC50, 1-4 microg/ml and MIC90, 2-16 microg/ml) were also susceptible to EGCg, although they appear to be slightly less susceptible to EGCg than C. glabrata and the other antifungal agents tested. Moreover, the susceptibility of Candida krusei strains (MIC50, 2 microg/ml and MIC90, 4-8 microg/ml) to EGCg was approximately 2- to 8-fold higher than those of 5FC and FLCZ. Our data indicate that EGCg can inhibit clinically pathogenic Candida species, although the concentrations of EGCg for antifungal susceptibility were slightly higher than those of tested antifungal agents on the whole. Based on these results, we suggest that EGCg may be effectively used as a possible agent or adjuvant for antifungal therapy in Candidiasis.     

Activities of therapeutic agents against Naegleria fowleri in vitro and in a mouse model of primary amebic meningoencephalitis

Inhalation of water contaminated with Naegleria fowleri may lead to a potentially fatal infection of the central nervous system known as primary amebic meningoencephalitis (PAM). Amphotericin B (AMB), an antifungal drug, is the only agent with established clinical efficacy in the treatment of PAM, though therapy with this drug is not always effective and has been associated with adverse effects on the kidneys and other organs. We investigated the activity of various therapeutic agents against N. fowleri in an attempt to identify other useful agents for treating PAM. Several of these agents exhibited in vitro activity against the Lee (M67) strain of N. fowleri. The minimum inhibitory concentrations of these agents were 0.1 microg/ml (ketoconazole), 1 microg/ml (liposomal AMB), and 10 microg/ml (minocycline, quinupristin-dalfopristin, and trifluoperazine). Other agents had a minimum inhibitory concentration > 10 microg/ml (linezolid) or > 100 microg/ml (rifampin). In a mouse model of PAM, none of the untreated control mice survived, whereas the survival of treated animals was 50% (quinupristin-dalfopristin), 30% (ketoconazole and liposomal AMB), 20% (trifluoperazine), and 10% (linezolid and minocycline). Further studies are needed to ascertain whether these agents have synergistic activity with AMB in vitro and in vivo.     

Purification and characterization of novel antifungal compounds from the sourdough Lactobacillus plantarum strain 21B

Sourdough lactic acid bacteria were selected for antifungal activity by a conidial germination assay. The 10-fold-concentrated culture filtrate of Lactobacillus plantarum 21B grown in wheat flour hydrolysate almost completely inhibited Eurotium repens IBT18000, Eurotium rubrum FTDC3228, Penicillium corylophilum IBT6978, Penicillium roqueforti IBT18687, Penicillium expansum IDM/FS2, Endomyces fibuliger IBT605 and IDM3812, Aspergillus niger FTDC3227 and IDM1, Aspergillus flavus FTDC3226, Monilia sitophila IDM/FS5, and Fusarium graminearum IDM623. The nonconcentrated culture filtrate of L. plantarum 21B grown in whole wheat flour hydrolysate had similar inhibitory activity. The activity was fungicidal. Calcium propionate at 3 mg ml(-1) was not effective under the same assay conditions, while sodium benzoate caused inhibition similar to L. plantarum 21B. After extraction with ethyl acetate, preparative silica gel thin-layer chromatography, and chromatographic and spectroscopic analyses, novel antifungal compounds such as phenyllactic and 4-hydroxy-phenyllactic acids were identified in the culture filtrate of L. plantarum 21B. Phenyllactic acid was contained at the highest concentration in the bacterial culture filtrate and had the highest activity. It inhibited all the fungi tested at a concentration of 50 mg ml(-1) except for P. roqueforti IBT18687 and P. corylophilum IBT6978 (inhibitory concentration, 166 mg ml(-1)). L. plantarum 20B, which showed high antimold activity, was also selected. Preliminary studies showed that phenyllactic and 4-hydroxy-phenyllactic acids were also contained in the bacterial culture filtrate of strain 20B. Growth of A. niger FTDC3227 occurred after 2 days in breads started with Saccharomyces cerevisiae 141 alone or with S. cerevisiae and Lactobacillus brevis 1D, an unselected but acidifying lactic acid bacterium, while the onset of fungal growth was delayed for 7 days in bread started with S. cerevisiae and selected L. plantarum 21B.     

Atropurosides A-G, new steroidal saponins from Smilacina atropurpurea

Atropurosides A-G (1-7), seven new steroidal saponins, which possess new polyhydroxylated aglycones, were isolated from the rhizomes of Smilacina atropurpurea (Convallariaceae), together with a known saponin, dioscin (8). Their structures were elucidated on the basis of detailed spectroscopic analysis, including 1D and 2D NMR techniques and chemical methods. Antifungal testing of the eight compounds indicated that atropurosides B (2) and F (6) were fungicidal against Candida albicans, Candida glabrata, Cryptococcus neoformans, and Aspergillus fumigatus with minimum fungicidal concentrations (MFCs) < or = 20 microg/ml, while dioscin (8) was selectively active against C. albicans and C. glabrata (MFC < or = 5.0 microg/ml). Furthermore, the antifungal saponins 2, 6, and 8 were evaluated for their in vitro cytotoxicities in a panel of human cancer cell lines (SK-MEL, KB, BT-549, SK-OV-3, and HepG2) and non-cancerous Vero cells. All showed moderate cytotoxicities. It appears that the antifungal activity of these steroidal saponins correlates with their cytotoxicity against mammalian cells.     

Antifungal activities of Bacillus thuringiensis isolates on barley and cucumber powdery mildews

Fourteen Bacillus thuringiensis isolates having both insecticidal activity and in vitro antifungal activity were selected and tested for in vivo antifungal activity against tomato late blight, wheat leaf rust, tomato gray mold, and barley powdery mildew in growth chambers. All the isolates represented more than 70% disease control efficacy against at least one of four plant diseases. Specifically, 12 isolates exhibited strong control activity against barley powdery mildew. Under glasshouse conditions, four (50-02, 52-08, 52-16, and 52- 18) of the isolates also displayed potent control efficacy against cucumber powdery mildew. To our knowledge, this is the first report of B. thuringiensis isolates that have disease control efficacy against powdery mildew of barley and cucumber as well as insecticidal activity.