Halorosellins A and B, unique isocoumarin glucosides from the marine fungus Halorosellinia oceanica

Structurally unique isocoumarin glucosides, named halorosellins A ( 1) and B ( 2), were isolated from the EtOAc extract of a broth of the marine fungus Halorosellinia oceanica. Other new minor metabolites including 4,8-dihydroxy-6-methoxy-4,5-dimethyl- 3-methyleneisochroman-1-one (3), 3-acetyl-7-hydroxy-5-methoxy-3,4-dimethyl-3-H-isobenzofuran-1-one ( 4) and an ophiobolane sesterterpene, 17-dehydroxyhalorosellinic acid ( 5), were also isolated. Structures of these compounds were elucidated by analyses of spectroscopic data. Compound 4 exhibited mild antimycobacterial activity (MIC value of 200 mug mL(-1)).