Napyradiomycin A4 and Its Relate Compounds, a New Anti-PRV Agent and Their Antibacterial Activities, from Streptomyces kebangsaanensis WS-68302

Two new napyradiomycins derivatives, napyradiomycin A4 ( ) and A80915 H ( ), along with five known ones, were isolated from the ethyl acetate extract of fermentation culture of WS-68302. Their structures were elucidated by extensive spectroscopic analysis, including HR-MS, 1D and 2D NMR, CD spectrum, as well as comparison with literature data. Compound exhibited significant antiviral activity against PRV (Pseudorabies virus) with an IC value of 2.056 μM and therapeutic ratio at 14.98, suggesting that it might have potential for development of an antiviral agent. Moreover, compound displayed the strongest inhibition against PRV protein among the tested napyradiomycins in the indirect immunofuorescence assay. Compounds and showed higher activities against swine pathogenic than the positive control penicillin G sodium salt, with MIC values of 3.125 and 6.25 μg/mL, respectively. Compounds and - exhibited moderate antibacterial activity against the swine pathogenic , with MIC values ranging from 25 to 50 μg/mL.