<i>S</i>-Bridged Thioether and Structure-Diversified Angucyclinone Derivatives from the South China Sea-Derived <i>Micromonospora echinospora</i> SCSIO 04089
Zhuangjie Fang, Xiaodong Jiang, Qingbo Zhang, Liping Zhang, Wenjun Zhang, Chunfang Yang, Haibo Zhang, Yiguang Zhu, Changsheng Zhang
Abstract
Angucyclinces belong to the class of aromatic polyketides and display a wide variety of structure diversity and pharmaceutical significance. Herein we report the isolation, structure elucidation, and bioactivity evaluation of structure-diversified angucyclinone derivatives and anthracene from the South China Sea-derived Micromonospora echinospora SCSIO 04089, including a thioether, gephysulfuromycin (1), two new benzo[b]phenanthridines, homophenanthroviridone (2) and homophenanthridonamide (3), a new benzo[b]fluorene, homostealthin D (4), a new naphtho[2,3-b]benzofuran, nenesfuran (5), a new naphthoquinone, WS-5995 D (6) and a new anthracene, nenesophanol (7), together with three known compounds (8–10). Their structures were elucidated by extensive spectroscopic analyses. The structures of 1–3 and 5–8 were confirmed by X-ray crystallographic analyses. Gephysulfuromycin (1) featured a rare single S-bridged 3,12a-epithiotetraphene skeleton. Homophenanthroviridone (2) was found to be cytotoxic to SF-268, MCF-7, and HepG2 cell lines with IC50 values of 5.4 ± 0.4, 6.8 ± 0.3, and 1.4 ± 0.1 μM, respectively. Compound 2 was also active against Gram-positive bacteria with MIC (minimal inhibition concentration) values ranging 2–4 μg mL–1.