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 IC 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 (IC, 20.0 μM). [ABSTRACT FROM AUTHOR]