Microbial Transformation of -Clerodane Diterpenoid, Scutebarbatine F, by sp. CPCC 205437.

Biotransformation of the -clerodane diterpene, scutebarbatine F (), by sp. CPCC 205437 was investigated for the first time, which led to the isolation of nine new metabolites, scutebarbatine F-F (-). Their structures were determined by extensive high-resolution electrospray ionization mass spectrometry (HRESIMS) and NMR data analyses. The reactions that occurred included hydroxylation, acetylation, and deacetylation. Compounds - and - possess 18-OAc fragment, which were the first examples of 13-spiro -clerodanes with 18-OAc group. Compounds - were the first report of 13-spiro -clerodanes with 2-OH. Compounds - were biologically evaluated for the cytotoxic, antiviral, and antibacterial activities. Compounds , , and exhibited cytotoxic activities against H460 cancer cell line with inhibitory ratios of 46.0, 42.2, and 51.1%, respectively, at 0.3 μM. Compound displayed a significant anti-influenza A virus activity with inhibitory ratio of 54.8% at 20 μM, close to the positive control, ribavirin.