Antifungal substances against pathogenic fungi, talaroconvolutins, from Talaromyces convolutus
ABSTRACT The dichloromethane extract of Talaromyces convolutus cultivated on barley exhibited antifungal activity against Candida albicans. In the course of a search for the active compounds, four new tetramic acid derivatives, talaroconvolutins A (1), B (2), C (3), and D (4), were isolated along with ZG-1494alpha (5), and mitorubrin derivatives. The structures of talaroconvolutins A-D (1-4) were established on the basis of spectroscopic and chemical investigations and chemical correlations. The antifungal activity of the talaroconvolutins against the pathogenic fungi Aspergillus fumigates, Aspergillus niger, C. albicans, and Cryptococcus neoformans was determined.
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ABSTRACT: The maize endophyte Acremonium zeae is antagonistic to kernel rotting and mycotoxin producing fungi Aspergillus flavus and Fusarium verticillioides in cultural tests for antagonism, and interferes with A. flavus infection and aflatoxin contamination of preharvest maize kernels. Chemical studies of an organic extract from maize kernel fermentations of Acremonium zeae (NRRL 13540), which displayed significant antifungal activity against Aspergillus flavus and F. verticillioides, revealed that the metabolites accounting for this activity were two newly reported antibiotics pyrrocidines A and B. Pyrrocidines were detected in fermentation extracts for 12 NRRL cultures of Acremonium zeae isolated from maize kernels harvested in Illinois (4/4 cultures), North Carolina (5/5), Georgia (1/2) and unrecorded locations within the USA (2/2). Pyrrocidine B was detected by LCMSMS in whole symptomatic maize kernels removed at harvest from ears of a commercial hybrid that were wound-inoculated in the milk stage with A. zeae (NRRL 13540) or (NRRL 13541). The pyrrocidines were first reported from the fermentation broth of an unidentified filamentous fungus LL-Cyan426, isolated from a mixed Douglas Fir hardwood forest on Crane Island Preserve, Washington, in 1993. Pyrrocidine A exhibited potent activity against most Gram-positive bacteria, including drug-resistant strains, and was also active against the yeast Candida albicans. In an evaluation of cultural antagonism between 13 isolates of A. zeae in pairings with A. flavus (NRRL 6541) and F. verticillioides (NRRL 25457), A. zeae (NRRL 6415) and (NRRL 34556) produced the strongest reaction, inhibiting both organisms at a distance while continuing to grow through the resulting clear zone at an unchanged rate. Maximum colony diameters for A. zeae (NRRL 6415) and (NRRL 13540), on potato dextrose agar after 14 d, were attained within the range of 25-30 degrees C, with less growth recorded at 15 degrees and 37.5 degrees and no growth at 5 degrees. Potential interactions between A. zeae and other maize endophytes are considered and the significance of these interactions relative to the aflatoxin and fumonisin contamination of preharvest maize is presented. This is the first report of natural products from Acremonium zeae.Mycological Research 06/2005; 109(Pt 5):610-8. DOI:10.1017/S0953756205002820 · 2.81 Impact Factor
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ABSTRACT: Abstract The antifungal activities of 65 extracts were evaluated through the agar well diffusion method in 22 plant samples from the Ucumari Natural Regional Park (UNRP). These samples belong to 20 plant species related to the following botanic families: Asteraceae, Euphorbiaceae, Melastomataceae, Podocarpaceae, Rubiaceae and Solanaceae. The plant extracts were obtained in hexanes, dichloromethane and methanol. The 65 extract samples were tested against pathogenic fungi Aspergillus fumigatus (ATCC 1022), Candida albicans (ATCC 18804) and Fusarium solani (ATCC 11712). Ketoconazole was used as positive control. The methanol extracts from Solanum spp. (FJR 3155) and Tibouchina grossa exhibited the greatest inhibitory activity against the three fungi tested, while the methanol extracts from Hyeronima macrocarpa, Miconia lehmannii, and Sapium stylare inhibited two of the fungi assayed. The dichloromethane extracts from Miconia lehmannii Cong, Lycinathes acutifolia and Solanum spp. (FJR 3155) inhibited two of the three fungi tested, while the dichloromethane extracts from Cinchona pubescens Vahl and Palicourea spp. (FJR 3182) inhibited one of the three microorganism tested. Only one of the hexane extracts produced activity against the three fungi tested.Pharmaceutical Biology 09/2008; 41(7):491-496. DOI:10.1080/13880200308951341 · 1.34 Impact Factor
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ABSTRACT: Studies of N-(hydroxymethyl)benzamide derivatives have concluded that the hydroxide-dependent reaction occurs via a specific-base catalyzed deprotonation of the hydroxyl group followed by rate-determining loss of the benzamidate and generation of the aldehyde. The 3-methyl, 4-methyl, and 4-methoxy-N-(hydroxymethyl)benzamide reaction mechanism deviates at higher [HO−] with amidic hydrolysis becoming competitive and having reaction half-lives of ∼17s, in 1M KOH, I=1.0M (KCl), 25°C. An intramolecular general-base catalyzed mechanism has been suggested for the amidic hydrolysis reaction.Tetrahedron Letters 12/2009; 50(52):7358-7361. DOI:10.1016/j.tetlet.2009.10.069 · 2.39 Impact Factor