ivate caspases that subsequently regulate nuclear export of the viral RNP complexes. Therefore, we investigated whether Inhibition of influenza virus-induced NF-kB activation in A549 cells by compound 1 The activation of NF-kB signaling pathway is a prerequisite for influenza virus infection. The specific inhibitors of NF-kB, 11 Antiviral Lignan Glycoside from C. gigantea inhibiting NF-kB activation by compound 1 could block nuclear export of viral RNP in the infected A549 cells. As a result, we observed that compound 1 treatment efficiently impaired nuclear export of the viral RNP in the infected A549 cells. This indicated that anti-influenza virus effect of compound 1 was predominantly through its NF-kB-inhibiting activity to suppress viral RNP export and subsequent virus propagation. that compound 1 targeted the early phase events of cellular NF-kB activation for virus replication. Further study is required to explore the detailed mechanism by which compound 1 exerts inhibitory effect on influenza replication and nuclear export of viral RNP. Conclusions A novel lignan glycoside, -pinoresinol 4-O-b-D-glucopyranoside and two known phenolic compounds, 69O-vanilloyltachioside and 69-O-vanilloylisotachioside were isolated MedChemExpress PR-619 PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19661824 from the latex of C. gigantea for the first time. The structure of new compound was established by using both spectroscopic methods and chemical reaction. Three isolates and an authentic -pinoresinol 4-O-b-D-glucopyranoside were screened for their anti-influenza activities by using CPE assay. It was found that compound 1 exhibited anti-influenza activity, while the other three compounds did not show such activity against an influenza virus strain A/PR/8/34. Discrepancy in anti-influenza viruses activity between compound 1 and -pinoresinol 4-O-b-D-glucopyranoside, revealed the necessity of a vanilloyl moiety in compound 1 for its anti-influenza activity. Further investigation of its anti-influenza viral spectrum by CPE assay and PRA indicated that compound 1 possesses specific antiviral activity against a panel of human influenza viruses while shows no inhibitory activity towards avian influenza viruses. A preliminary mechanistic study showed that compound 1 suppresses an early stage of viral replication. Compound 1 inhibited A/PR/8/34 virus-induced phosphorylation of p65 in a dose-dependent manner, and significantly suppressed the translocation of the phosphorylated p65 into the nucleus, indicating that compound 1 possesses inhibitory effect on the virus-induced activation of NF-kB. In addition, compound 1 blocked the 
nuclear export of the viral RNP, which was irrelevant to the virus-induced activation of Raf/MEK/ERK signaling pathway. It was concluded that the anti-influenza virus activity of compound 1 closely correlates with its NF-kBinhibiting activity. Our studies suggested that this novel lignan glycoside might be a promising candidate for the research and development of antiviral agents specifically targeting human influenza viruses. Discussion Infection with influenza virus is still one of the severe threats worldwide, which caused significant morbidity and mortality. On March 30 in 2013, a novel multiple-reassortant avian influenza A subtype H7N9 infection was identified in eastern China. The emergence of oseltamivir resistance of clinical isolates of H7N9 has been associated with Arg292Lys mutation in the virus neuraminidase gene. Thus, there is an urgent need to explore and develop new anti-influenza drugs. Di
