Abstract: Tea polyphenols gallocatechin (GC), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG),epigallocatechin gallate (EGCG), protocatechuic aldehyde (PAD) and protocatechuic acid (PA) were evaluated for their ability to inhibit influenza virus in MDCK cells. Among these compounds, the EGCG and ECG showed a marked antiviral effect against influenza virus infections in MDCK cells and this effect was observed in all influenza virus subtypes tested, including H₅N₁, H₁N₁ and H₉N₂ virus. The 50% effective inhibitory concentrations (EC₅₀) of EGCG and ECG for three virus subtypes were 0.04~0.11 mmol/L and 0.05~0.07 mmol/L, respectively, which were less than the EC₅₀ value of ribavirin(0.41~0.53 mmol/L) in MDCK cells. All these tea polyphenols tested showed an inhibitory effect on the neuraminidases (NAs) from H₅N₁, H₁N₁ and H₉N₂ viruses. The 50% effective inhibitory concentrations (IC₅₀) of EGCG and ECG for three NAs from virus subtypes were 0.03~0.14 mmol/L and 0.34~0.69 mmol/L, respectively. The inhibitory effect of EGCG and ECG on the NAs was similar to their antiviral effect in MDCK cells, which suggested their anti-influenza effect was due to their inhibition on the NAs. In addition, the inhibitory effect on mice infected by influenza virus of extracts from C. assamica var. Kucha containing 85% polyphenolics was evaluated. At the concentration of 1 000 mg/(kg·d), the extracts possessed potent inhibitory effect on BALB/c’s pneumonia consolidation infected by influenza viruses. The inhibition of the extracts on lung index was 37%.

Key words: polyphenolics, influenza virus, neuraminidase, mice, pneumonia, MDCK cell