Two novel metabolites ofAspergillus fonsecaeus

Reassessing the Structure of Pyranonigrin

“…Pyranonigrin A (1), seen as the major UV peak in the chromatogram shown in Figure 2, was readily isolated from solid fermentations of culture LL-LV3020 by extracting the solids with MeOH followed by resin adsorption on HP20 and chromatography on Sephadex LH-20. Fraction 9 of the Sephadex LH-20 chromatography yielded nearly white, solid material of pyranonigrin A (1) that contained a small amount of its congener pyranonigrin S (2). Repeated attempts to obtain crystalline material by slow evaporation of the solvent were unsuccessful and apparently resulted in some decomposition, as judged by darkening (browning) of the solution.…”

“…In our search for natural products with potential application in human or animal health, we examined methanolic extracts of the marine fungus Aspergillus niger (culture LL -LV3020) and recognized a number of naphtho-γ-pyrone metabolites with fonsecin as the principal member along with its dehydrated versions rubrofusarin and asperflavone and several dimeric derivatives such as auranosperone B. , Another group of secondary metabolites was identified as the dicoumarins kotanin, demethylkotanin, and orlandin, which were coproduced with nigragillin, atromentin, and citric acid. , In fact, the level of citric acid present in the culture extracts was so overwhelming (ca. 35 g/L) that this amount was the root cause of perturbation in the various enzymatic assays.…”

Phytotoxic Compounds from the New Coprophilous Fungus Guanomyces polythrix

“…Compounds 1 − 5 are new natural products and were characterized by spectroscopic and chiroptical methods as (2 S ,3 S )-5-hydroxy-6,8-dimethoxy-2,3-dimethyl-4 H -2,3-dihydronaphtho[2,3- b ]-pyran-4-one ( 1 ); (2 S ,3 S )-5-hydroxy-6,8,10-trimethoxy-2,3-dimethyl-4 H -2,3-dihydronaphtho[2,3- b ]-pyran-4-one ( 2 ); (2 S )-5-hydroxy-6,8-dimethoxy-2-methyl-4 H -2,3-dihydronaphtho[2,3- b ]-pyran-4-one ( 3 ); (2 S )-5-hydroxy-6,8,10-trimethoxy-2-methyl-4 H -2,3-dihydronaphtho[2,3- b ]-pyran-4-one ( 4 ); and 5-hydroxy-6,8-dimethoxy-2,3-dimethyl-4 H -naphtho[2,3- b ]-pyran-4-one ( 5 ). In addition, the known compounds rubrofusarin B ( 6 ), − emodin ( 7 ), , citrinin ( 8 ), , and 4-hydroxybenzoic acid methyl ester ( 9 ) were obtained. The spectral properties of the known compounds, including IR, 1 H NMR, and 13 C NMR data, were identical to those previously described in the literature.…”

“…The phytotoxic activity was found in secondary fraction FVI-6, eluted with CH 2Cl2-MeOH (99:1). Further purification of this fraction by preparative TLC (CH2Cl2) yielded 6 (7.1 mg), 5 (7 EIMS m/z 300 [M + (100)], 282 (25), 271 (65), 254 (15), 229 (12), HRMS m/z 300.0994 (calcd for C17H16O5, 300.0997).…”