Two new members of streptothricin class antibiotics from Streptomyces qinlingensis sp. nov.

Four streptothricin-group antibiotics (14) were isolated from the fermentation broth of Streptomyces qinlingensis sp. nov. Along with the known antibiotics streptothricins F (1) and D (3), two new members of this class (2, 4) were identified as 12-carbamoyl derivatives of 1 and 3, respectively, mainly by analysis of the IR, HR-MS and NMR spectral data. The antibacterial activities of 14 against Escherichia coli (MICs 3.1, 25.0, 3.1 and 12.5 microg/ml), Bacillus subtilis (MICs 6.3, 25.0, 3.1 and 50 microg/ml), Staphylococcus aureus (MICs 12.5, >100.0, 6.3, >100.0 microg/ml), Bacillus cereus (MICs 25.0, 50.0, 25.0 and 50.0 microg/ml) and Pseudomonas aeruginosa (MICs 50.0, >100.0, 50.0, >100.0 microg/ml) were assayed by micro-broth dilution. The results based on MIC data indicated that 2 and 4 exhibited significantly less potent antibacterial activities when compared to that of 1 and 3.