Antiviral effectiveness of Sarcandra glabra and Fragaria vesca extracts against influenza A H1N1

Background: Influenza is an acute respiratory disease which occurs globally with high annual attack rate estimated at 5–10% in adults and 20–30% in children. Although vaccines and antivirals are available for preventing influenza infections, the infectious rate still high due to viral mutations. Therefore, it is essential for human health to explore more antiviral substances which inhibit influenza disease. Natural products have been widely used as traditional medicines and applied in antimicrobial and antiseptic purpose for a long time, for example, Sarcandra glabra (SG) and Fragria vesca (FV). Previous studies have reported that both of them are able to strengthen human immunity and reduce inflammation symptoms. However, both of them have not been shown to against influenza A/H1N1 virus which is similar to seasonal influenza but it has higher fatality rates among healthy young adults and higher incidence of viral pneumonia. Hence, the aim of the study is to reveal if these nature product extracts have virucidal effectiveness on influenza A H1N1 virus. Methods and materials: Both extracts from SG and FV are extracted using a modified reflux extraction method. MDCK cells was used to evaluate the toxicity of both extracts and 10 TCID50 influenza A/PR/8/1934 (H1N1) was used to determine the virucidal effectiveness of both extracts in several conditions, includes the treatment of pre- and post-infection as well as neutralization of the extracts. The results were verified by TCID assay. Results: Our finding showed that either SG or FV, both have significant inhibition effect for influenza A/H1N1 virus especially in the condition of 1 h neutralization, their IC50 were 20.03 μg/mL and 25.41 μg/mL, respectively. The average IC50 of pre- and post-infection treatment were 23.91 μg/mL and 23.65 μg/mL in SG and 41.56 μg/mL and 25.82 μg/mL in FV. The CC50 of both extracts to MDCK cells showed was >100 μg/mL. Conclusion: In summary, the extracts of SG or FV extracted by our modified protocol, have contained potential antiviral compounds against influenza A/H1N1 virus replication and able to develop as a health food product.