Isocoumarins from Spegazzinia sp. MDCW-573 with Antibacterial and Proangiogenic Activities

Twelve new isocoumarins, spegazmarins A–L (1–12), including nine novel dimeric derivatives (1–9), three monomeric derivatives (10–12), as well as eight known ones (13–20), were isolated from the endophytic fungus Spegazzinia sp. MDCW-573. Their structures were elucidated by analysis of NMR, X-ray crystallography, and ECD data. Notably, the dimeric isocoumarins (1–9) possess a unique linkage, where the phenyl of one monomer is connected to the lactone of another. The methods for determining the configurations of both the monomeric and dimeric isocoumarins within this class were proposed, leading to the correction of the configurations of two previously reported isocoumarins. The isolated compounds inhibited Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, with MIC values of 1 to 64 μg/mL. Compounds 5, 6, and 12 significantly promoted the growth of zebrafish intersegmental vessels at concentrations of 10, 20, and 40 μM, respectively.