Pontophenazine, a new Phenazine Analog from Marine-Derived Streptomyces sp. CNQ-031

Objective: This study aimed to isolate and identify bioactive secondary metabolites, including a new phenazine derivative, from a marine-derived Streptomyces sp. CNQ-031 belonging to the MAR4 clade, and to evaluate their antibacterial activity. Methods: The marine-derived Streptomyces sp. was cultivated and extracted using ethyl acetate. The crude extracts were subjected to chromatographic separation to afford a new natural product, pontophenazine (1), along with known compounds, 1-methoxyphenazine (2), 5,7-dihydroxy-2-(1-methylpropyl)-4H-chromen-4-one (3), and 5,7-dihydroxy-2-isopropyl-4H-chromen-4-one (4). The chemical structure of 1 was elucidated through analysis of nuclear magnetic resonance (NMR) and mass spectrometry (MS) data, while the chemical structures of 2−4 were identified by comparing their NMR data with those of previously reported compounds. Antibacterial activity was assessed using the broth microdilution method. Results: Four compounds were isolated, including a new phenazine derivative, pontophenazine (1) from a marine-derived Streptomyces sp. CNQ-031. This compound exhibited antibacterial activity against B. subtilis KCTC 1021, with a minimum inhibitory concentration (MIC) value of 64 μg/mL, showed significant biofilm inhibition towards A. tumefaciens SND195, and P. aeruginosa SNC165 (35.4 ± 1.1%, 19.7 ± 0.8%, respectively), and displayed weak inhibitoryactivity against M. luteus and S. aureus in the quorum-sensing assay. Conclusion: The discovery of pontophenazine (1) expands the structural diversity of marine-derived phenazine derivatives and highlights the MAR4 Streptomyces clade as a valuable source of new antibacterial compounds.