Keumja Yun

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. Compounds 1-4 exhibited mild antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus, and multidrug-resistant S. aureus. The MIC values of each strain were as follows: compounds 1 and 2 showed an MIC of 15.6 μg/mL against S. aureus, methicillin-resistant S. aureus, and multidrug-resistant S. aureus, and compounds 3 and 4 exhibited an MIC of 31.5 μg/mL against S. aureus and methicillin-resistant S. aureus and 62.5 μg/mL against multidrug-resistant S. aureus.

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 CaBr2 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. Compounds 1–3, and a mixture of 4 and 5 exhibited radical‐scavenging activities against 1,1‐diphenyl‐2‐picrylhydrazyl with IC50 values of 18, 15, 42, and 6 μM, respectively. With the exception of 3, the compounds were, therefore, more active than the positive control, ascorbic acid (IC50 20 μM).

New production of haloquinones, bromochlorogentisylquinones A and B, by a halide salt from a marine isolate of the fungus Phoma herbarum

New production of haloquinones, bromochlorogentisylquinones A and B, by a halide salt from a marine isolate of the fungus Phoma herbarum

New production of (R)-(–)-5-bromomellein, a dihydroisocoumarin derivative from the marine-derived fungus Aspergillus ochraceus

The addition of NaBr to the fermentation of a marine isolate of the fungus Aspergillus ochraceus resulted in induced production of a new brominated mellein analogue. A new radical-scavenging halogenated isocoumarin, (R)-(–)-5-bromomellein (1), and three known compounds, (R)-(–)-mellein (2), clavatol (3), and circumdatin A (4), were isolated from the culture. The structure of 1 was assigned through a combination of spectroscopic data analyses. Compounds 1–4 exhibited mild radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH). The IC50 values of each compounds (1–4) were 24, 25, 30, and 32 μM, respectively, which were less active than the positive control, L-ascorbic acid (IC50, 20.0 μM).

Oxysporizoline, an antibacterial polycyclic quinazoline alkaloid from the marine-mudflat-derived fungus Fusarium oxysporum

Oxysporizoline, an antibacterial polycyclic quinazoline alkaloid from the marine-mudflat-derived fungus Fusarium oxysporum

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). Compound 1 also displayed cytotoxic activity against human cervical carcinoma (HeLa) cells, with an IC50 value of 0.5 µM.