Cytospyrone and Cytospomarin: Two New Polyketides Isolated from Mangrove Endophytic Fungus, Cytospora sp.

Abstract

Two new polyketides, cytospyrone (<b>1</b>), cytospomarin (<b>2</b>), together with three known metabolites dimethoxyphtalide (<b>3</b>), integracin A (<b>4</b>) and integracin B (<b>5</b>), were isolated from the culture of <i>Cytospora</i> sp. from the Chinese mangrove <i>Ceriops tagal</i>. Their structures were elucidated by extensive spectroscopic analyses and time dependent density functional theory (TDDFT), calculation of electronic circular dichroism (ECD) and optical rotation (OR) data. Compound <b>2</b> displayed weak inhibitory activity against <i>Escherichia coli</i> GIM1.201 (minimum inhibitory concentration (MIC) value of 0.35 mM). Compounds <b>4</b> and <b>5</b> displayed significant cytotoxicity against human cancer cell line HepG2 (IC₅₀ values of 5.98 ± 0.12 µM and 9.97 ± 0.06 µM, respectively), more potent than the positive control 5-fluorouracil (IC₅₀ value of 43.50 ± 3.69 µM).