Cytotoxic and antibacterial marfuraquinocins from the deep South China Sea-derived Streptomyces niveus SCSIO 3406.

Four new sesquiterpenoid naphthoquinones, marfuraquinocins A-D (1-4), and two new geranylated phenazines, phenaziterpenes A (5) and B (6), 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 1-6 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, 1 and 3 were found to inhibit a NCI-H460 cancer cell line with IC50 values of 3.7 and 4.4 μM, respectively. Compounds 1, 3, and 4 exhibited antibacterial activities against Staphylococcus aureus ATCC 29213 with equivalent MIC values of 8.0 μg/mL; compounds 3 and 4 each showed antibacterial activity against methicillin-resistant Staphylococcus epidermidis (MRSE) shhs-E1 with MIC values of 8.0 μg/mL.