Abstract：The maximum safe concentration(MNTC) of Desmodium caudatum extracts (DCE) on
MDCK cells was determined by CCK8 method. The model of MDCK cells infected with influenza vi‐
rus A/PR8/34(H1N1, PR8) was established, and its inhibitory effect on cytopathic changes caused by
viral infection was detected using CCK8 method. Using fluorescence quantitative PCR method, the ef‐
fects of DCE on influenza virus genes，proteins and expression of host inflammatory transcription fac‐
tors and inflammatory cytokines were detected. The cytotoxicity test results showed that the MNTC of
DCE on MDCK cells was 100 mg/L.The qRT-PCR results showed that DCE could significantly re‐
duce mRNA expression of M and NP genes of PR8 influenza virus （P<0.01）， and also significantly
downregulated the expression levels of inflammatory transcription factors NF- κB p65 and STAT3，and inflammatory cytokines IL-1β and TNF-α，whose inhibitory effect was positively correlated with
drug concentration. Immunoblotting assay showed that DCE of high concentration （100 mg/L） sig‐
nificantly inhibited the expression of influenza virus M1 protein （P<0.01）. These results indicate
that Desmodium caudatum extracts have significant in vitro anti-influenza virus effects， and lays
foundation for identifying the exact pharmacological components with anti influenza virus effects
from Desmodium caudatum.
