Mersaquinone, A New Tetracene Derivative from the Marine-Derived Streptomyces sp. EG1 Exhibiting Activity against Methicillin-Resistant Staphylococcus aureus (MRSA)

New antibiotics are desperately needed to overcome the societal challenges being encountered with methicillin-resistant Staphylococcus aureus (MRSA). In this study, a new tetracene derivative, named Mersaquinone (1), and the known Tetracenomycin D (2), Resistoflavin (3) and Resistomycin (4) have been isolated from the organic extract of the marine Streptomyces sp. EG1. The strain was isolated from a sediment sample collected from the North Coast of the Mediterranean Sea of Egypt. The chemical structure of Mersaquinone (1) was assigned based upon data from a diversity of spectroscopic techniques including HRESIMS, IR, 1D and 2D NMR measurements. Mersaquinone (1) showed antibacterial activity against methicillin-resistant Staphylococcus aureus with a minimum inhibitory concentration of 3.36 μg/mL.