Antibacterial natural products lobophorin L and M from the marine-derived Streptomyces sp. 4506

Abstract

Two new spirotetronate natural products, lobophorin L (1) and lobophorin M (2), together with three known lobophorin-like spirotetronate antibiotics (3–5) and two known ansamycins (6–7), were isolated from the marine-derived Streptomyces sp. 4506. The structures of 1 and 2 were established on the basis of HRESIMS as well as 1D and 2D NMR datasets. Antibacterial assay showed that, compounds 1 and 3–5 exhibited strong to moderate antibacterial activities against Micrococcus luteus and Bacillus thuringiensis with MIC values ranging from 0.0625 to 8 μg/mL, while compounds 3 and 6 showed weak antibacterial activities against Staphylococcus aureus and MRSA. The antibacterial activities of the lobophorins in this study indicated that the more substitution number of the sugar moieties at C-9 of the lobophorin, the stronger antimicrobial properties it may deserve, and the higher the oxidation degree of substituent group at C-3_D, the better antibacterial activities of its corresponding compound could be.

Graphical Abstract

Keywords:

• Lobophorin L and M
• marine Streptomyces
• antibacterial activity
• ansamycin derivatives

Acknowledgments

The authors thank Yun Zhang at South China Sea Institute of Oceanology, Chinese Academy of Sciences for HRESIMS measurements.

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

This research was supported by the National Key R&D Program of China (2018YFA0903200), the Open Funding Project from State Key Laboratory of Microbial Metabolism (MMLKF18-11) and the Fundamental Research Funds for the Central Universities.