Induced production of 6,9-dibromoflavasperone, a new radical scavenging naphthopyranone in the marine-mudflat-derived fungus Aspergillus niger.

The addition of metal bromides (NaBr and CaBr2) during fermentation of the marine-mudflat-derived fungus Aspergillus niger induced production of a new radical scavenging brominated naphthopyranone, 6,9-dibromoflavasperone (1); and three known naphtho-γ-pyranone monomers, flavasperone (2), TMC-256A1 (3), and fonsecin (4); and one naphtho-γ-pyranone dimer, aurasperone B (5). The structure of 6,9-dibromoflavasperone (1) was assigned through the combination of spectroscopic data analyses and comparison with the spectral data of flavasperone (2). Compounds 1-5 displayed potent radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, with IC50 values of 21, 25, 0.

Cristazine, a New Cytotoxic Dioxopiperazine Alkaloid from the Mudflat-Sediment-Derived Fungus Chaetomium cristatum.

Cristazine (1), a new class of dioxopiperazine alkaloid, along with previously isolated chetomin (2), neoechinulin A (3), and golmaenone (4), were isolated from the mudflat-sediment-derived fungus Chaetomium cristatum. The structure and absolute stereochemistry of 1 was assigned on the basis of NMR, electron impact (EI)-MS, tandem FAB-MS/MS, and circular dichroism (CD) experiments. Compounds 1-4 displayed potent radical-scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH), with IC50 values of 19, 15, 24, and 20 µM, respectively, which were similar to that of the positive control, ascorbic acid (IC50, 20 µM).

Induced production of methyl bromodihydroxyphenyl acetates by the marine-derived fungus Aspergillus sp.

The addition of metal bromides (NaBr and CaBr2) during fermentation of a marine isolate of the fungus Aspergillus sp. induced production of two new brominated dihydroxyphenylacetic acid derivatives, methyl 2-(6-bromo-3,4-dihydroxyphenyl)acetate (1) and methyl 2-(2,5-dibromo-3,4-dihydroxyphenyl)acetate (2), and a known compound, 2-(3,4-dihydroxyphenyl)acetic acid (3). The structures of the two new compounds (1, 2) were assigned through the combination of spectroscopic data analyses and comparison with the spectral data of compound 3.

New production of 5-bromotoluhydroquinone and 4-O-methyltoluhydroquinone from the marine-derived fungus Dothideomycete sp.

The addition of NaBr to the fermentation medium of a marine isolate of the fungus Dothideomycete sp. resulted in induced production of two toluhydroquinone derivatives, 5- bromotoluhydroquinone (1) and 4-O-methyltoluhydroquinone (2), and two known compounds, toluhydroquinone (3) and gentisyl alcohol (4). The structures of 1 and 2 were assigned through the spectroscopic data analyses.

Flavusides A and B, antibacterial cerebrosides from the marine-derived fungus Aspergillus flavus.

Flavusides A (1) and B (2), two new antibacterial cerebroside derivatives, and the previously described phomaligol A (3), kojic acid (4), methyl kojic acid (5), and dimethyl kojic acid (6) have been isolated from the extract of a marine isolate of the fungus Aspergillus flavus. The structure and absolute stereochemistry of two cerebrosides were assigned on the basis of NMR and Tandem FAB-MS/MS experiments. Compounds 1, 2, and 3 exhibited a mild antibacterial activity against Staphylococcus aureus, methicillin-resistant S.

Microbial mannosidation of bioactive chlorogentisyl alcohol by the marine-derived fungus Chrysosporium synchronum.

The biological transformation of the biologically active chlorogentisyl alcohol (1), isolated from the marine-derived fungus Aspergillus sp., was studied. Preparative-scale fermentation of chlorogentisyl alcohol with marine-derived fungus Chrysosporium synchronum resulted in the isolation of a new glycosidic metabolite, 1-O-(α-D-mannopyranosyl)chlorogentisyl alcohol (2).

Induced production of bromomethylchlamydosporols A and B from the marine-derived fungus Fusarium tricinctum.

The addition of CaBr(2) to the fermentation of a marine-derived Fusarium tricinctum resulted in production of halogenated chlamydosporol analogues. Two new antimicrobial halogenated pyranopyranones, bromomethylchlamydosporols A (1) and B (2), and two known compounds, chlamydosporol (an inseparable epimeric mixture of 7R:7S = 1:1 from (1)H NMR data) (3) and fusarielin A (4), were isolated from the culture. The structures of 1 and 2 were assigned through a combination of spectroscopic data analyses.

Induced production of halogenated diphenyl ethers from the marine-derived fungus Penicillium chrysogenum.

Manipulation of the fermentation of the marine-derived fungus Penicillium chrysogenum by addition of CaBr(2) resulted in induced production of bromodiphenyl ether analogs. Two new free-radical-scavenging polybrominated diphenyl ethers, 1 and 2, and three known diphenyl ethers, 3,3'-dihydroxy-5,5'-dimethyldiphenyl ether (3), and an inseparable mixture of violacerol-I (4) and violacerol-II (5) were isolated. The structures of the two new polybromodiphenyl ethers 1 and 2 were assigned by combined spectroscopic-data analysis, including deuterium-induced isotope effect.

Biotransformation of bioactive (-)-mellein by a marine isolate of bacterium Stappia sp.

The biological transformation of the bioactive dihydroisocoumarin, (-)-mellein, isolated from the marine-derived fungus Cladosporium sp., was studied. The preparative-scale culture of (-)-mellein with a marine isolate of a bacterium Stappia sp.