Lobophorins E and F, new spirotetronate antibiotics from a South China Sea-derived Streptomyces sp. SCSIO 01127.

The strain SCSIO 01127, isolated from the South China Sea sediment, was identified as a member of Streptomyces by the 16S rDNA sequence analysis. Two new spirotetronate antibiotics lobophorins E (1) and F (2), along with two known analogs lobophorins A (3) and B (4), were isolated from Streptomyces sp. SCSIO 01127. Their structures were elucidated on the basis of detailed IR, NMR and MS spectroscopic analyses. The new compound lobophorin F (2) showed antibacterial activities against Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 with MIC values of 8 μg ml(-1) for both the strains, better than that of lobophorin B (4). Lobophorin F (2) also displayed better cytotoxic activities than lobophorin B (4), with IC(50) of 6.82, 2.93 and 3.16 μM against SF-268, MCF-7 and NCI-H460, respectively.