Cytotoxic and Antibacterial Marfuraquinocins from the Deep South China Sea-Derived Streptomyces niveus SCSIO 3406

Abstract

Four new sesquiterpenoid naphthoquinones, marfuraquinocins A–D (<b>1</b>–<b>4</b>), and two new geranylated phenazines, phenaziterpenes A (<b>5</b>) and B (<b>6</b>), were isolated from the fermentation broth of Streptomyces niveus SCSIO 3406, which originated from a South China Sea sediment sample obtained from a depth of 3536 m. The structures of <b>1</b>–<b>6</b> were elucidated on the basis of extensive MS and one-dimensional and two-dimensional NMR spectroscopic analyses. In a panel of cytotoxicity and antibacterial assays, <b>1</b> and <b>3</b> were found to inhibit a NCI-H460 cancer cell line with IC₅₀ values of 3.7 and 4.4 μM, respectively. Compounds <b>1</b>, <b>3</b>, and <b>4</b> exhibited antibacterial activities against Staphylococcus aureus ATCC 29213 with equivalent MIC values of 8.0 μg/mL; compounds <b>3</b> and <b>4</b> each showed antibacterial activity against methicillin-resistant Staphylococcus epidermidis (MRSE) shhs-E1 with MIC values of 8.0 μg/mL