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During the screening programme for antibiotic produced by actinomycetes, an antibiotic was isolated from the fermentation broth of Streptomyces anulatus NEAE-94. The ethyl acetate extract of S. anulatus NEAE-94 showed high biological activity against Staphylococcus aureus NRRL B-313, multidrug-resistant S. aureus and Bacillus subtilis NRRL B-543. Thin-layer chromatography of the ethyl acetate extract showed one yellowish orange spot with an Rf value of 0.83. The structural elucidation of the isolated compounds was carried out using ultraviolet–visible mass spectrometry (MS), Fourier transform-infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H-NMR) and gas chromatography–mass spectrometry (GC–MS) analyses. Characterization of the ethyl acetate extract revealed the presence of 22 compounds, including an unsaturated fatty acid, saturated fatty acids, fatty acid esters, alkanes, alkenes and a triterpene. The antimicrobial efficacy of S. anulatus NEAE-94 might be due to the synergistic effects of the identified compounds.

Four glutarimide-derived compounds including a new 3-[2-[2-hydroxy-3-methylphenyl-5-(hydroxymethyl)]-2-oxoethyl] glutarimide (1) and three known 3-[2-(2-hyroxy-3,5- dimethylphenyl)-2-oxoethyl] glutarimide (2, actiphenol), 3-hydroxy-3-[2-(2-hydroxy-3,5-dimethylphenyl)-2-oxoethyl] glutarimide (3) and 3-[2-[2-hydroxy-3-(hydroxymethyl)-5-methylphenyl]-2-oxoethyl] glutarimide (4), along with a known indole alkaloid 3-(hydroxyacetyl) indole (5), were isolated from ethyl acetate extract of the fermentation broth of the marine sponge-derived Streptomyces anulatus S71. Their structures were deduced by extensive studies of NMR and mass spectra.