Hetiamacin E and F, New Amicoumacin Antibiotics from Bacillus subtilis PJS Using MS/MS-Based Molecular Networking

To combat escalating levels of antibiotic resistance, novel strategies are developed to address the everlasting demand for new antibiotics. This study aimed at investigating amicoumacin antibiotics from the desert-derived Bacillus subtilis PJS by using the modern MS/MS-based molecular networking approach. Two new amicoumacins, namely hetiamacin E (1) and hetiamacin F (2), were finally isolated. The planar structures were determined by analysis of extensive NMR spectroscopic and HR–ESI–MS data, and the absolute configurations were concluded by analysis of the CD spectrum. Hetiamacin E (1) showed strong antibacterial activities against methicillin-sensitive and resistant Staphylococcus epidermidis at 2–4 µg/mL, and methicillin-sensitive and resistant Staphylococcus aureus at 8–16 µg/mL. Hetiamacin F (2) exhibited moderate antibacterial activities against Staphylococcus sp. at 32 µg/mL. Both compounds were inhibitors of protein biosynthesis demonstrated by a double fluorescent protein reporter system.