pH modulation of zopfiellin antifungal activity to Colletotrichum and Botrytis

Zopfiellin, a novel cyclooctanoid natural product isolated from Zopfiella curvata No. 37-3, was evaluated in a 96-well microtiter assay for fungicidal activity against Botrytis cinerea, Colletotrichum acutatum, Colletotrichum fragariae, Colletotrichum gloeosporioides, and Fusarium oxysporum. Zopfiellin exhibited pH-dependent activity, with the most mycelial growth inhibition demonstrated at pH 5.0. Mass spectrometry and nuclear magnetic resonance spectroscopy studies indicated that zopfiellin undergoes structural changes with changes in pH. At pH 5.0, zopfiellin showed the greatest activity against B. cinerea (IC(80) = 10 microM), C. gloeosporioides (IC(80) = 10 microM), and C. fragariae (IC(80) = 10 microM) and intermediate activity against C. acutatum (IC(80) = 30 microM), and was not active against F. oxysporum (IC(80) > 100 microM).     

Isolation and identification of antifungal fatty acids from the basidiomycete Gomphus floccosus

Bioautography of extracts of the fruiting bodies of the basidiomycete Gomphus floccosus (Schw.) Singer indicated the presence of fungitoxic compounds in the ethyl acetate fraction against the plant pathogens Colletotrichum fragariae, Colletotrichum gloeosporioides, and Colletotrichum acutatum. Bioassay-guided fractionation of this fraction resulted in the isolation of the bioactive fatty acids (9 S,10 E,12 Z)-9-hydroxy-10,12-octadecadienoic acid (1), (9 E,11 Z)-13-oxo-9,11-octadecadienoic acid (2), and (10 E,12 E)-9-oxo-10,12-octadecadienoic acid (3). These three oxylipins were further evaluated for activity against a greater range of fungal plant pathogens (C. fragariae, C. gloeosporioides, C. acutatum, Botrytis cinerea, Fusarium oxysporum, Phomopsis obscurans, and Phomopsis viticola) in in vitro dose-response studies. Phomopis species were the most sensitive fungi to these compounds. At 120 h of treatment, the IC50 values for compounds 1, 2, and 3 for P. obscurans were 1.0, 4.5, and 23 microM, respectively, as compared to 1.1 microM for the captan positive control.     

Activity of quinones on colletotrichum species

The antifungal activity of 1,4-naphthoquinones, 1,2-naphthoquinones, 1,4-benzoquinones, and anthraquinones from our natural products collection was tested by direct bioautography to identify natural products with potential use in agricultural fungal pathogen control. Quinones demonstrated good to moderate antifungal activity against Colletotrichum spp. Colletotrichum fragariae was the most sensitive species to quinone-based chemistry, Colletotrichum gloeosporioides had intermediate sensitivity, while Colletotrichum acutatum was the species least sensitive to these compounds.     

Characterization of volatile constituents of Haplopappus greenei and studies on the antifungal activity against phytopathogens

Essential oil of Haplopappus greenei A. Gray was obtained by hydrodistillation of aerial parts, which were subsequently analyzed by gas chromatography and gas chromatography-mass spectrometry. Major components were identified as carvacrol (8.7%), beta-pinene (7.6%), trans-pinocarveol (6.2%), and caryophyllene oxide (5.8%), respectively. In total, 104 components representing 84.9% of the investigated essential oil were characterized. Furthermore, the essential oil was evaluated for antimalarial, antimicrobial, and antifungal activities. However, only antifungal activity was observed against the strawberry anthracnose-causing fungal plant pathogens Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides using the direct overlay bioautography assay. Major essential oil components were also evaluated for antifungal activity; the carvacrol standard demonstrated nonselective activity against the three Colletotrichum species and the other compounds were inactive.     

Chemical composition and antifungal activity of Arnica longifolia, Aster hesperius, and Chrysothamnus nauseosus essential oils

Essential oils from three different Asteraceae obtained by hydrodistillation of aerial parts were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). Main compounds obtained from each taxon were found as follows: Arnica longifolia carvacrol 37.3%, alpha-bisabolol 8.2%; Aster hesperius hexadecanoic acid 29.6%, carvacrol 15.2%; and Chrysothamnus nauseosus var. nauseosus beta-phellandrene 22.8% and beta-pinene 19.8%. Essential oils were also evaluated for their antimalarial and antimicrobial activity against human pathogens, and antifungal activities against plant pathogens. No antimalarial and antimicrobial activities against human pathogens were observed. Direct bioautography demonstrated antifungal activity of the essential oils obtained from three Asteraceae taxa and two pure compounds, carvacrol and beta-bisabolol, to the plant pathogens Colletotrichum acutatum, C. fragariae and C. gloeosporioides. Subsequent evaluation of antifungal compounds using a 96-well micro-dilution broth assay indicated that alpha-bisabolol showed weak growth inhibition of the plant pathogen Botrytis cinerea after 72 h.     

Antifungal activity of thiophenes from Echinops ritro

Extracts from 30 plants of the Greek flora were evaluated for their antifungal activity using direct bioautography assays with three Colletotrichum species. Among the bioactive extracts, the dichloromethane extract of the radix of Echinops ritro (Asteraceae) was the most potent. Bioassay-guided fractionation of this extract led to the isolation of eight thiophenes. Antifungal activities of isolated compounds together with a previously isolated thiophene from Echinops transiliensis were first evaluated by bioautography and subsequently evaluated in greater detail using a broth microdilution assay against plant pathogens Colletotrichum acutatum, Colletotrichum fragariae, Colletotrichum gloeosporioides, Botrytis cinerea, Fusarium oxysporum, Phomopsis viticola, and Phomopsis obscurans. 5'-(3-Buten-1-ynyl)-2,2'-bithiophen (1), alpha-terthienyl (2), and 2-[pent-1,3-diynyl]-5-[4-hydroxybut-1-ynyl]thiophene (5) at 3 and 30 microM were active against all three Colletotrichum species, F. oxysporum, P. viticola, and P. obscurans.     

Chemical composition and antifungal activity of Salvia macrochlamys and Salvia recognita essential oils

Essential oils of Salvia macrochlamys and Salvia recognita were obtained by hydrodistillation of dried aerial parts and characterized by gas chromatography and gas chromatography-mass spectrometry. One hundred and twenty identified constituents representing 97.7% in S. macrochlamys and 96.4% in S. recognita were characterized, and 1,8-cineole, borneol, and camphor were identified as major components of the essential oils. The oils were evaluated for their antimalarial, antimicrobial, and antifungal activities. Antifungal activity of the essential oils from both Salvia species was nonselective at inhibiting growth and development of reproductive stroma of the plant pathogens Colletotrichum acutatum, Colletotrichum fragariae, and Colletotrichum gloeosporioides. S. macrochlamys oil had good antimycobacterial activity against Mycobacterium intracellulare; however, the oils showed no antimicrobial activity against human pathogenic bacteria or fungi up to a concentration of 200 microg/mL. S. recognita oil exhibited a weak antimalarial activity against Plasmodium falciparum.     

Antifungal clerodane diterpenes from Macaranga monandra (L) Muell. et Arg. (Euphorbiaceae)

Hexane and ethyl acetate phases of the methanol extract of Macaranga monandra showed fungal growth inhibition of Colletotrichum acutatum, C. fragariae and C. gloeosporioides, Fusarium oxysporum, Botrytis cinerea, Phomopsis obscurans, and P. viticola. Bioassay-guided fractionation led to the isolation of two active clerodane-type diterpenes that were elucidated by spectroscopic methods (1D-, 2D-NMR, and MS) as kolavenic acid and 2-oxo-kolavenic acid. A 96-well microbioassay revealed that kolavenic acid and 2-oxo-kolavenic acid produced moderate growth inhibition in Phomopsis viticola and Botrytis cinerea.     

Phytotoxic and fungitoxic activities of the essential oil of kenaf (Hibiscus cannabinus L.) leaves and its composition

The chemical composition of the essential oil of kenaf (Hibiscus cannabinus) was examined by GC-MS. Fifty-eight components were characterized from H. cannabinus with (E)-phytol (28.16%), (Z)-phytol (8.02%), n-nonanal (5.70%), benzene acetaldehyde (4.39%), (E)-2-hexenal (3.10%), and 5-methylfurfural (3.00%) as the major constituents. The oil was phytotoxic to lettuce and bentgrass and had antifungal activity against Colletotrichum fragariae, Colletotrichum gloeosporioides, and Colletotrichum accutatum but exhibited little or no algicidal activity.     

Algicidal activity of stilbene analogues

Continuing our search for natural product and natural product-based compounds for the control of off-flavor in catfish, 29 stilbene analogues were synthesized and evaluated for algicidal activity against the 2-methylisoborneol (MIB)-producing cyanobacterium Oscillatoria perornata. The cis and trans isomers of 4-(3,5-dimethoxystyryl)aniline showed moderate and selective algicidal activity toward O. perornata with the lowest observed inhibitory concentration and lowest complete inhibition concentrations of 10 muM. This is the first report on selective stilbene algicidal activity toward a MIB-producing cyanobacteria species.     

Composition and some biological activities of the essential oil of Callicarpa americana (L.)

The essential oil profile of Callicarpa americana was examined. Samples were collected from Lafayette county in north central Mississippi, and GC-MS data and retention indices were used to identify 67 oil components. Humulene epoxide II (13.9%), alpha-humulene (10.0%), 7-epi-alpha-eudesmol (9.4%), beta-pinene (8.8%), and 1-octen-3-ol (8.5%) were the major components of the steam-distilled oil. The oil was selectively toxic toward the cyanobacterium Oscillatoria perornata compared to Oscillatoria agardhii and the green alga Selenastrum capricornutum, with complete growth inhibition at 28.5 microgram/mL. The oil was only mildly phytotoxic and antifungal.     

Natural fungicides from Ruta graveolens L. leaves,including a new quinolone alkaloid

Bioassay-directed isolation of antifungal compounds from an ethyl acetate extract of Ruta graveolens leaves yielded two furanocoumarins, one quinoline alkaloid, and four quinolone alkaloids, including a novel compound, 1-methyl-2-[6'-(3' ',4' '-methylenedioxyphenyl)hexyl]-4-quinolone. The (1)H and (13)C NMR assignments of the new compound are reported. Antifungal activities of the isolated compounds, together with 7-hydroxycoumarin, 4-hydroxycoumarin, and 7-methoxycoumarin, which are known to occur in Rutaceae species, were evaluated by bioautography and microbioassay. Four of the alkaloids had moderate activity against Colletotrichum species, including a benomyl-resistant C. acutatum. These compounds and the furanocoumarins 5- and 8-methoxypsoralen had moderate activity against Fusarium oxysporum. The novel quinolone alkaloid was highly active against Botrytis cinerea. Phomopsis species were much more sensitive to most of the compounds, with P. viticola being highly sensitive to all of the compounds.     

Antifungal constituents of the essential oil fraction of Artemisia dracunculus L. Var. dracunculus

The isolation and structure elucidation of antifungal constituents of the steam-distilled essential oil fraction of Artemisia dracunculus are described. Antifungal activities of 5-phenyl-1,3-pentadiyne and capillarin against Colletrotichum fragariae, Colletrotichum gloeosporioides, and Colletrotichum acutatum are reported for the first time. The relative abundance of 5-phenyl-1,3-pentadiyne is about 11% of the steam-distilled oil, as determined by GC-MS. Methyleugenol was also isolated and identified as an antifungal constituent of the oil.     

Synthesis of water-soluble 9,10-anthraquinone analogues with potent cyanobactericidal activity toward the musty-odor cyanobacterium Oscillatoria perornata

A series of water-soluble 9,10-anthraquinone analogues were prepared and evaluated for their selective toxicity toward Oscillatoria perornata, which grows in catfish production ponds and causes "musty" off-flavor in channel catfish ( Ictalurus punctatus). Water-soluble mono- and dicationic salts were prepared by conjugating various small amines directly or through a methylene or ethylene bridge to the 9,10-anthraquinone nucleus. One of the dicationic salts, 2-[ N-(1'-methyl-4'- N, N-diethylaminobutyl)aminometyl]anthraquinone diphosphate, exhibited very high water solubility and potent selective toxicity toward O. perornata. However, the tendency of this compound to potentially bind to suspended sediments may be the reason for its limitations in controlling O. perornata in catfish production ponds. The monocationic salt, 2-[ N-(1'-methylethyl)]aminomethyl]anthraquinone monophosphate, showed good solubility and high selective toxicity toward O. perornata. Neutral water-soluble analogues prepared by conjugating terta- or pentaethylene glycol directly or by a methylene bridge to the 9,10-anthraquinone nucleus had less activity than the parent compound.     

The antifungal activity of widdrol and its biotransformation by Colletotrichum gloeosporioides (penz.) Penz. & Sacc. and Botrytis cinerea Pers.: Fr

Widdrol (1) was tested against the necrotrophic plant pathogens Botrytis cinerea and Colletotrichum gloeosporioides. While 1 was found to be inactive against C. gloeosporioides, it showed a selective and effective control of B. cinerea, significantly inhibiting the mycelial growth of the fungus at concentrations of 100 ppm and above. In addition, the biotransformation of 1 by both fungi was studied. Incubation with C. gloeosporioides and B. cinerea afforded four and one biotransformation products (2-6), respectively. Biotransformation with C. gloeosporioides was highly regioselective, yielding for the most part oxidation products at C-10: 10-oxowiddrol (2), 10beta-hydroxywiddrol (3), 10alpha-hydroxywiddrol (4), and 14alpha-hydroxywiddrol (5). The structures of all products were determined on the basis of their spectroscopic data, including coupling constants, two-dimensional NMR analysis (heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation, and nuclear Overhauser enhancement spectroscopy), and nuclear Overhauser effect. The biotransformation products were then tested against B. cinerea and found to be inactive. These results shed further light on the structural modifications, which may be necessary to develop selective fungal control agents against B. cinerea.     

Antifungal activity of strawberry fruit volatile compounds against Colletotrichum acutatum

Eight volatile products characterizing strawberry aroma, which is generated from the oxidative degradation of linoleic and linolenic acids by a lipoxygenase (LOX) pathway, were examined because of their antifungal activity against Colletotrichum acutatum, one of the causal agents of strawberry anthracnose. In this study, the effects of aldehydes, alcohols, and esters on mycelial growth and conidia development were evaluated. (E)-Hex-2-enal was found to be the best inhibitor of mycelial growth [MID (minimum inhibitory doses)=33.65 microL L(-1)] and of spore germination (MID=6.76 microL L(-1)), while hexyl acetate was the least effective of all volatile compounds tested (MID=6441.89 microL L(-1) for mycelial growth and MID=1351.35 microL L(-1) for spore germination). Furthermore, the antifungal activity of (E)-hex-2-enal on susceptibility of strawberry fruits to C. acutatum was also confirmed. The presence of these molecules in jars containing strawberry fruits inoculated with a suspension of spores inhibited the fungus growth and prevented the appearance of symptoms. Moreover, a study of the effects of (E)-hex-2-enal on conidial cells of C. acutatum was evaluated by transmission electron microscopy. This volatile compound altered the structures of the cell wall and plasma membrane, causing disorganization and lysis of organelles and, eventually, cell death.     

Metabolites from Aspergillus fumigatus, an endophytic fungus associated with Melia azedarach, and their antifungal, antifeedant, and toxic activities

Thirty-nine fungal metabolites 1-39, including two new alkaloids, 12β-hydroxy-13α-methoxyverruculogen TR-2 (6) and 3-hydroxyfumiquinazoline A (16), were isolated from the fermentation broth of Aspergillus fumigatus LN-4, an endophytic fungus isolated from the stem bark of Melia azedarach. Their structures were elucidated on the basis of detailed spectroscopic analysis (mass spectrometry and one- and two-dimensional NMR experiments) and by comparison of their NMR data with those reported in the literature. These isolated compounds were evaluated for in vitro antifungal activities against some phytopathogenic fungi, toxicity against brine shrimps, and antifeedant activities against armyworm larvae (Mythimna separata Walker). Among them, sixteen compounds showed potent antifungal activities against phytopathogenic fungi (Botrytis cinerea, Alternaria solani, Alternaria alternata, Colletotrichum gloeosporioides, Fusarium solani, Fusarium oxysporum f. sp. niveum, Fusarium oxysporum f. sp. vasinfectum, and Gibberella saubinettii), and four of them, 12β-hydroxy-13α-methoxyverruculogen TR-2 (6), fumitremorgin B (7), verruculogen (8), and helvolic acid (39), exhibited antifungal activities with MIC values of 6.25-50 μg/mL, which were comparable to the two positive controls carbendazim and hymexazol. In addition, of eighteen that exerted moderate lethality toward brine shrimps, compounds 7 and 8 both showed significant toxicities with median lethal concentration (LC(50)) values of 13.6 and 15.8 μg/mL, respectively. Furthermore, among nine metabolites that were found to possess antifeedant activity against armyworm larvae, compounds 7 and 8 gave the best activity with antifeedant indexes (AFI) of 50.0% and 55.0%, respectively. Structure-activity relationships of the metabolites were also discussed.     

Release of acetaldehyde from beta-cyclodextrins inhibits postharvest decay fungi in vitro

Many naturally occurring plant volatiles are known to have antifungal properties. However, they have limited use because they diffuse rapidly in air. In this in vitro study, acetaldehyde was chosen as a prototype volatile in order to study the controlled release of antifungal volatiles from cyclodextrins (CD). The major postharvest pathogens Alternaria alternata, Botrytis cinerea, and Colletotrichum acutatum were exposed to the pure volatile for 7 days at 23 degrees C. Acetaldehyde was most effective against A. alternata, followed by C. acutatum, and B. cinerea, with 0.12, 0.56, and 1.72 microL/L in air being required to inhibit fungal growth, respectively, according to the bioassay developed. Second, the effectiveness of the new beta-CD-acetaldehyde release system was evaluated against A. alternata for 7 days at 23 degrees C. Sufficient volatile was released from 0.7 g of beta-CD-acetaldehyde to prevent fungal growth in vitro.     

沼液对植物病害的防治效果及机理研究Ⅰ：对植物病原真菌的抑制效果及抑菌机理初探

采用菌丝生长抑制和分生孢子萌发抑制的试验方法,以草莓枯萎病菌为靶标病原菌,研究了江苏省内运行稳定的21个大型沼气工程的沼液及其无菌滤液对草莓枯萎病菌的生长抑制特性。结果表明,所有沼气工程的沼液对草莓枯萎病菌的菌丝生长都有不同程度的抑制作用,不同运行年限的沼气池沼液以及不同发酵原料的沼液对草莓枯萎病菌的抑制效果均无显著差异,但不同贮液阶段的沼液对其抑菌效果影响显著。沼液的无菌滤液对草莓枯萎病菌菌丝的生长没有抑制作用;沼液及其无菌滤液对草莓枯萎病菌分生孢子的萌发均有不同程度的抑制作用,猪粪沼液及其无菌滤液对草莓枯萎病菌分生孢子萌发的抑制作用好于牛粪沼液。沼液对生产上常见的5种植物病原真菌的抑制效果有显著差别。沼液中的拮抗微生物是沼液抑菌防病的主要因子。     

苹果炭疽菌低毒性菌株的筛选及控病效果

苹果炭疽菌(Colletotrichum gloeosporioides)感染能对苹果采后造成严重经济损失,利用弱致病菌株先侵入寄主组织后诱发植物产生抗病性,可以减轻植物病害的发生和危害。本研究利用离子注入和交变磁场处理的方法诱导产生苹果炭疽菌的低毒株,并进行筛选。通过调查菌株生长情况及在苹果上发生的病斑的大小,获得低毒株,对其在苹果上的保护作用进行测定,发现离子注入C100-2-5低毒株和磁场处理C0.25-1-2低毒株对苹果有较好的保护作用。