Fig. 2.

a – d The effect of preparations on the neuraminidase inhibition (NI50, mean mg/ml) of influenza virus strains H3N2 (a), H1N1 (b), H5N3 (c) and H7N1 (d). Tested viruses were diluted in enzyme buffer and aliquots of 25 μl of each dilution were added to the wells. As a positive control, enzyme buffer were used, instead of virus-containing material. After incubation for 30 min at 37 °C, 50 μl aliquot of substrate solution was added to each well and the plate was incubated at room temperature for 30 min. 150 μl aliquots of stop-solution buffer were added to the wells and optical density was measured by the “Tecan” spectrophotometer. The capacity of tested preparations to inhibit of neuraminidase activity of influenza viruses was estimated as effective concentration of tested preparations (EIC₅₀, mg/ml) capable to inhibit 50% of neuraminidase activity (NI₅₀)