New Pyridinium Compound from Marine Sediment-Derived Bacterium Bacillus licheniformis S-1

The structural diversity of marine natural products is considered a potential resource for the pharmaceutical industry. In our study of marine-derived compounds, one bacterium <i>Bacillus licheniformis</i> S-1 was discovered to have the ability to produce bioactive natural products. After a further chemistry investigation, one novel 4-aminopyridinium derivative, 4-(dimethylamino)-1-(2<i>S</i>-((4hydroxybenzoyl)oxy)propyl)pyridin-1-ium (<b>1</b>), along with 15 known cyclic dipeptides (<b>2</b>-<b>16</b>) were isolated from the bacterium <i>B. licheniformis</i> S-1 derived from a shallow sea sediment. The structures of compounds <b>1</b>-<b>16</b> were elucidated through comprehensive NMR spectroscopic and specific optical rotation (OR) data analyses. Compound <b>6</b> showed antibacterial activity against <i>Pseudomonas fulva</i> with an MIC value of 50 µg/mL. This is the first study to discover a pyridinium derivative and cyclic dipeptides from <i>B. licheniformis.</i>