Anthraquinones from a Marine-Derived Streptomyces spinoverrucosus

Four new anthraquinone analogues including galvaquinones A–C (1–3) and an isolation artifact, 5,8-dihydroxy-2,2,4-trimethyl-6-(3-methylbutyl)anthra[9,1-de][1,3]oxazin-7(2H)-one (4), were isolated from a marine-derived Streptomyces spinoverrucosus based on activity in an image-based assay to identify epigenetic modifying compounds. The structures of 1–4 were elucidated by comprehensive NMR and MS spectroscopic analysis. Galvaquinone B (2) was found to show epigenetic modulatory activity at 1.0 μM and exhibited moderate cytotoxicity against non-small-cell lung cancer (NSCLC) cell lines Calu-3 and H2887.