Three new naphthoquinone-based meroterpenoids from Streptomyces sp. HBERC-16614 with antibacterial activities

Three new naphthoquinone-based meroterpenoids (1-3), including spironaphthomeroterpenoid (1), a novel naphthoquinone-based meroterpenoid with a rare [5, 6] spiro-ring skeleton, and naphthablins D and E (2-3), along with three known analogues (4-6) were isolated from Streptomyces sp. HBERC-16614. The structures of these compounds, including their absolute configurations, were established by extensive spectroscopic analysis and electronic circular dichroism (ECD) spectrum. The antibacterial activities of compounds (1-6) were evaluated against Staphylococcus aureus, Streptococcus suis, and Escherichia coli. Among them, compound 1 demonstrated potent antibacterial activity against S. aureus, with a minimum inhibitory concentration (MIC) value of 3.13 µg/mL.