Anti-influenza and anti-inflammatory effects of green tea (Camellia sinensis L.) extract

Pulmonary complications due to influenza A virus infection, in addition to being caused by the replication of the virus, are partly due to the excess production of pro-inflammatory cytokines. It is therefore helpful to seek out compounds to control the excess production of these cytokines along with administration of antiviral drugs. In this study, the effect of green tea (Camellia sinensis L.) extract on the replication of influenza A (H1N1) virus and on gene expression levels of pro-inflammatory cytokines was studied in Madin-Darby canine kidney (MDCK) cells. 

In this experimental study, hydroalcoholic extract of C. sinensis leaf was prepared with maceration method. In vitro anti-influenza virus activity of the extract was evaluated by performing hemagglutination (HA) and 50 % tissue culture infectious dose (TCID50) assays at 24 and 48 hours of incubation. The gene expression levels of pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α), interleukin 1 beta (IL- 1β) and IL-6 were studied using real-time Polymerase chain reaction (PCR) 24 hours after treatment. 

Camellia sinensis extract treatment caused a significant decrease in viral titer compared to control virus in a dose-dependent manner (P < 0.05). The gene expression levels of IL-6, TNF-α and IL-1β after treatment with the extract decreased significantly compared to the virus control (P < 0.05). 

Due to its antiviral effect and reducing the gene expression of pro-inflammatory cytokines, C. sinensis extract can be used as an adjunctive drug along with current antiviral drugs in severe influenza infection as well as other viral infections, such as coronavirus, to minimize lung damage due to inflammation.