Nocarbenzoxazoles A–G, Benzoxazoles Produced by Halophilic Nocardiopsis lucentensis DSM 44048

Abstract

Seven new benzoxazole derivatives, nocarbenzoxazoles A–G (<b>1</b>–<b>7</b>), were isolated from the halophilic strain Nocardiopsis lucentensis DSM 44048. Their structures were elucidated on the basis of 1D and 2D NMR spectroscopic data, HRESIMS, and X-ray single-crystal diffraction. The isolated compounds were assayed for their cytotoxicity against a panel of human tumor cell lines (HepG2, MDA-MB-231, MDA-MB-435, HeLa, and PC3). Compounds <b>1</b>–<b>6</b> were found to have modest or no activity. Compound <b>7</b> showed selective activity against HepG2 and HeLa with IC₅₀ values of 3 and 1 μM, respectively