Neuraminidase inhibitors from marine-derived actinomycete Streptomyces seoulensis

Aims: This work was performed to characterize new secondary metabolites with neuraminidase (NA) inhibitory activity from marine actinomycete strains.

Methods and results: An actinomycete strain IFB-A01, capable of producing new NA inhibitors, was isolated from the gut of shrimp Penasus orientalis and identified as Streptomyces seoulensis according to its 16S rRNA sequence (over 99% homology with that of the standard strain). Repeated chromatography of the methanol extract of the solid-substrate culture of S. seoulensis IFB-A01 led to the isolation of streptoseolactone (1), and limazepines G (2) and H (3). The structures of 1-3 were determined by a combination of IR, ESI-MS, 1D ((1) H and (13) C NMR, and DEPT) and 2D NMR experiments (HMQC, HMBC, (1) H-(1) H COSY and NOESY). Compounds 1-3 showed significant inhibition on NA in a dose-dependent manner with IC50 values of 3.92, 7.50 and 7.37 μmol l(-1), respectively.

Conclusions: This is the first report of two new (1 and 2) and known (3, recovered as a natural product for the first time in the work) NA inhibitors from the marine-derived actinomycete S. seoulensis IFB-A01.

Significance and impact of the study: The three natural NA inhibitors maybe of value for the development of drug(s) necessitated for the treatment of viral infections.