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-3H-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 µg mL−1).