Phenazinoates A‒E, five pairs of phenazine conjugates from a mangrove soil-derived Streptomyces strain OUCMDZ-4923

Phenazinoates A–E ( 1 – 5 ), comprising five pairs of methyl saphenate conjugates with genistein, o -aminophenol, p -acetaminophenol and glycerol, were isolated from the fermentation broth of mangrove soil-derived Streptomyces sp. OUCMDZ-4923. Their structures were determined through comprehensive one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy, coupled with high-resolution electrospray ionization mass spectrometry. The absolute configurations of each isomer were established by comparing experimental electronic circular dichroism spectra with calculated counterparts. Based on the biosynthetic pathway analysis, compounds 1 ‒ 3 were semi-synthesized from the reactions of methyl ( R )-saphenate with genistein, o -aminophenol, and o -formamidophenol, utilizing microwave-assisted solid acid catalysis. The compounds were resolved as enantiomerically pure forms and subsequently tested for antibacterial efficacy against six pathogenic bacteria. Phenazinoates A ( 1 ) and B ( 2 ) demonstrated bioactivity against four Gram-positive bacterial strains, with minimum inhibitory concentration values ranging from 0.78 to 3.13 μg/mL.