Pestalotiopisorin B, a new isocoumarin derivative from the mangrove endophytic fungus <i>Pestalotiopsis</i> sp. HHL101

A new isocoumarin derivative pestalotiopisorin B (1), along with six known compounds, (R)-(-)- mellein methyl ether (2), pestalotiopyrone G (3), (R)-mevalonolactone (4), pestalotiollides A–B (5–6) and pestalotiopsol A(7) were isolated from Pestalotiopsis sp., an endophytic fungus obtained from Chinese mangrove plant Rhizophora stylosa. Their structures were elucidated unambiguously by the comprehensive analysis of extensive spectroscopic data. Compound 1 exhibited modest antibacterial activity against Escherichia coli and Pseudomonas aeruginosa with 12.5 μg/ml, 50 μg/ml, respectively. Compound 4 showed moderate calcineurin inhibitory activity towards p-nitrophenyl phosphate (IC50 =134.29 ± 5.377 μM).