Sporminarins A and B: Antifungal Metabolites from a Fungicolous Isolate of Sporormiella minimoides

Abstract

Cultures of a fungicolous isolate of Sporormiella minimoides afforded two new polyketide metabolites which we have named sporminarins A (1) and B (2). The planar structures of 1 and 2 were elucidated by analysis of NMR and MS data, and by chemical methods. 1 exhibited significant antifungal activity against Aspergillus flavus. Keywords sporminarins, antifungal, Sporormiella minimoides IntroductionOur ongoing studies of mycoparasitic and fungicolous fungi have shown them to be excellent sources of new biologically active natural products [1ϳ4]. In the course of this ongoing project, we examined cultures of a fungicolous isolate of Sporormiella minimoides Ahmed & Cain (Sporormiaceae; NRRL 37629) that was obtained from a basidioma of Trametes hirsutum collected from a dead hardwood branch in a subalpine dry forest in Hawaii. The ethyl acetate extract obtained from solid-state fermentation cultures of S. minimoides exhibited antifungal activity against Aspergillus flavus. The extract was fractionated using silica gel column chromatography, and the resulting fractions were subjected to reversed-phase HPLC to yield two new metabolites, which we have named sporminarins A (1) and B (2). The known compound brocaenol A was also obtained, and was identified by comparison of NMR and MS data with literature values [5]. Details of the isolation, structure elucidation, and bioactivities of 1 and 2 are presented here. Results and DiscussionSporminarin A (1) was assigned a molecular formula of C 36 H 62 O 8 (six degrees of unsaturation) on the basis of NMR (Table 1) and HRESIMS data. 1 H NMR analysis of 1 in CDCl 3 gave poor spectra, with considerable overlap and broad signals, but spectra recorded in CD 3 OD were of much better quality. 1 H, 13 C NMR, and DEPT data for 1 revealed the presence of six olefinic protons, five oxymethines, six non-oxygenated methines, three nonoxygenated methylenes, and 11 methyl groups. These units accounted for 56 protons, indicating that the remaining six protons must be exchangeable. The methyl group 1 H NMR signals consisted of two olefinic methyl resonances lacking vicinal coupling, two aliphatic methyl singlets, six CH 3 -CH doublets, and one CH 3 -CH 2 triplet. The 13 C NMR spectrum of 1 revealed 35 discrete signals, one short of the expected count, suggesting that two of the signals were coincident. Only seven signals were distinguishable in the olefinic region of the 13 C NMR spectrum of 1, and the DEPT spectrum contained six of those signals, indicating that the overlapped signal must correspond to one of two nonprotonated olefinic carbons. also revealed the presence of two oxygenated quaternary sp 3 carbons, and an oxycarbonyl carbon (d C 179.9) that was presumed to be a carboxylic acid group, although chemical shift alone could not definitively rule out an ester unit [6]. Treatment of 1 with trimethylsilyldiazomethane yielded the corresponding methyl ester (COOCH 3 methyl signal at d H 3.69), thereby confirming the presence of the carboxylic acid group. Of the six degrees of uns...

Kipukasins, Nucleoside Derivatives from Aspergillus versicolor

“…Compound 1 (2.4 mg) was treated with 0.1 N NaOH (0.5 mL) at room temperature for 48 h. The solution was evaporated to dryness and purified by RP-HPLC using 0.1% formic acid in H 2 …”

“…However, initial analyses indicated the presence of a set of major constituents unrelated to sterigmatocystin. Further investigation afforded five new nucleoside derivatives, which we named kipukasins A-E (1)(2)(3)(4)(5). At the same time, analysis of extracts from cultures of a different fungicolous isolate of A. versicolor (also from Hawaii, but from a different location) led to recognition of the presence of a similar set of compounds.…”

Epicoccalone, a Coumarin‐Type Chymotrypsin Inhibitor, and Isobenzofuran Congeners from an Epicoccum sp. Associated with a Tree Fungus

“…[25] The structure of 1 is suggestive for a polyketide pathway leading to the unusual coumarin. Unfortunately though, 13 C isotope labeling studies were hampered by the low production of 1 (0.2 mg L -1 ). However, we identified two cometabolites (2 and 3) that could shed light on the biogenesis of 1.…”

“…[1][2][3] In the kingdom fungi this is well reflected by so-called mycophilic fungi [4][5][6][7][8] and plant endophytes, [9,10] as well as fungicolous or mycoparasitic fungi. [11][12][13] Another rare example in which the fungus serves as a host are the fungal-bacterial symbioses producing the toxins rhizoxin [14][15][16] and rhizonin. [17] In the course of our search for bioactive compounds produced by tree fungi, [18][19][20][21][22] we have identified an Epicoccum species growing within the fruit body of the tree fungus Pholiota squarrosa.…”

Isolation of Chromanone and Isobenzofuran Derivatives from a Fungicolous Isolate of Epicoccum purpurascens

“…Silica gel column chromatography of fraction 15 (58 mg) using 10:1 CHCl 3 -MeOH provided compound 4 (37 mg, R f 0.34 in 9:1 CHCl 3 -MeOH). Silica gel column chromatography of fraction 16 (25 mg) using 9:1 CHCl 3 -MeOH provide a subfraction (8.5 mg), which was further purified by reversed-phase HPLC eluting with a 30-100% CH 3 …”