Sharkquinone, a new ana-quinonoid tetracene derivative from marine-derived Streptomyces sp. EGY1 with TRAIL resistance-overcoming activity

A new ana -quinonoid tetracene metabolite, named sharkquinone ( 1 ), and the known SS-228R ( 2 ) have been isolated from the ethyl acetate extract of the culture of marine Streptomyces sp. EGY1. The strain was isolated from sediment sample collected from the Red Sea coast of Egypt. The structure of sharkquinone ( 1 ) was elucidated using detailed spectral (HRESI-MS, 1D and 2D NMR) analyses and quantum chemical calculations. This is the first report of the isolation of ana -quinonoid tetracene derivative from a natural source. Compound 1 showed the ability to overcome tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) resistance at a concentration of 10 μM in human gastric adenocarcinoma (AGS) cells.