4.7. Neuraminidase Inhibition Assay

A neuraminidase inhibition assay was conducted according to the NA-Fluor influenza Neuraminidase Assay Kit (Life Technologies, Carlsbad, CA, USA). DS was serially diluted from 40 μM to 1.25 μM, and oseltamivir carboxylate (Aobious Inc., MA, USA), a specific neuraminidase inhibitor, was serially diluted from 1 μM to 0.0001 μM. H1N1 IAV was added to each sample, mixed and incubated for 30 min, followed by the addition of the NA-Fluor substrate for 1 h at 37 °C. After stopping the reaction, neuraminidase activity was detected with a fluorescence spectrometer (Promega, Madison, WI, USA) with excitation at 365 nm and emission at 445 nm.