Bioactive ambuic acid congeners from endophytic fungus Pestalotiopsis trachicarpicola SC-J551

New ambuic acid derivatives, pestallic acids R-V (1-5), together with ambuic acid (6), were isolated from the endophytic fungus Pestalotiopsis trachicarpicola SC-J551 derived from the fern Blechnum orientale L., of which compound 2, being racemic, was separated to two optically pure enantiomers (+)-2 and (-)-2. The structures including absolute configurations of these new compounds were elucidated by extensive spectroscopic analysis and theoretical simulations of their ECD spectra and ¹³C NMR chemical shifts. Compounds 1 and 3 exhibited cytotoxicity against human carcinoma A549, HeLa, HepG2, and MCF-7 cells (IC₅₀: 3.6-12.5 μM) and compound 3 was also active against Staphylococcus aureus and MRSA (MIC = 20 μg ml^-1). Compound (±)-2 showed inhibitory activity against LPS-induced NO release (IC₅₀ = 21.1 μM) and t-BHP-induced ROS production (IC₅₀ = 8.5 μM) in RAW264.7 macrophages.