Actinomycetoquinones A–E, Anthraquinone-γ-Pyrones Discovered from Marine-Derived Actinomycetospora sp. Bacterium

Facilitated by LC–MS–PCA metabolomics methods and effective molecular networking for strain prioritization and dereplication, five new anthraquinone-γ-pyrones, actinomycetoquinones A–E (1–5), were isolated from a marine-derived Actinomycetospora sp. bacterium. The structures of 1–5 were elucidated by analysis of their HRMS and NMR spectroscopic data. The absolute configuration of 1 was unequivocally determined by single-crystal X-ray diffraction analysis using Cu Kα radiation. Actinomycetoquinone C exhibited antibacterial activity against methicillin-resistant S. aureus (MRSA) and E. coli with MIC values of 1 and 4 μg/mL, respectively.