Neuraminidase Inhibitors from the Roots of Caragana sinica.

Two new oligostilbenes, caragasinins D and E, along with four known compounds, kobophenol A, α-viniferin, wistin, and 5-hydroxy-2-[(4-hydroxyphenyl)acetyl]-3-methoxybenzoic acid, were isolated from the roots of Caragana sinica. These compounds were spectroscopically analyzed for their structures and configurations and compared with existing data. The configurations of caragasinins D and E were elucidated by 1 H-NMR spectroscopy, CD spectroscopy, and time-dependent density-functional theory simulated ECD spectral data. All six compounds were evaluated for their inhibitory activity against neuraminidase (NA) from Clostridium perfringens. Among the tested compounds, 5-hydroxy-2-[(4-hydroxyphenyl)acetyl]-3-methoxybenzoic acid demonstrated statistically significant NA inhibitory activity, which was comparable to the positive control, mangiferin.