Table 2.

Direct antiviral action of plant extracts against influenza A virus A/Teal/Tunka/7/2010 (H3N8)

Extract	NI ± SD *	ID50% **
Gentiana decumbens, 1% extract	1.4 ± 0.7	-
Hypecoum erectum, 1% extract	4.8 ± 0.2	8.6
Polygonum bistorta, 1% extract	1.6 ± 0.1	-
Terminalia chebula, 0.5% extract	4.9 ± 0.2	13.4
Momordica cochinchinensis, 0.5% extract	5.1 ± 0.3	2.7
DEVA-5, 1% extract	1.6 ± 0.4	-
H3N2 Abs, diluted as 1:100	93.9 ± 0.7	59.1

* - approximately 1 × 10⁵ PFU of A/Teal/Tunka/7/2010 (H3N8) were used for the NI assay.

** - approximately 200 PFU of A/Teal/Tunka/7/2010 (H3N8) were used for the PRNT assay.

The neutralisation index (NI) was estimated as the quotient of the virus concentration in the water-treated sample to the virus concentration in the test sample. The 50% inhibition dose was estimated using probit analysis as the maximal reciprocal dilution of extract that inhibited the formation of plaques by 50%.