Inhibition of influenza virus via a sesquiterpene fraction isolated from Laggera pterodonta by targeting the NF-κB and p38 pathways

Background: Influenza virus poses serious threats to human health, especially human infection with avian influenza virus. Laggera pterodonta (DC.) Benth is a medicinal plant that is widely used in Traditional Chinese Medicine, especially in Yunnan province, and has been used to treat influenza, pharyngolaryngitis, and bronchitis. However, the compound(s) responsible for the activity and their mechanisms of action against the influenza virus remain to be elucidated. Methods: L. pterodonta extract was fractionated, and the active fraction was identified as Fraction 14 (Fr 14). Fr 14 was further analysed and characterized by ultra-high-performance liquid chromatography hyphenated with quadrupole-time of flight mass spectrometry (UHPLC/Q-TOF-MS). The inhibitory effect against influenza virus was evaluated using a cytotoxicity assay. Then, cytokines and chemokines were detected by qRT-PCR and a bio-plex assay. Signalling pathways that inhibited the influenza virus were identified using a western blotting assay. Results: The active fr 14 showed a wide spectrum of anti-influenza virus activity. The pharmacological mechanisms showed that Fr 14 acts on the early stage of virus replication (0-6 h). It inhibited the p38/MAPK pathway and then inhibited the NF-kappa B pathway and COX-2. Fr 14 also prevented the increased expression of cytokines and chemokines. Conclusion: This study demonstrated the preliminary mechanisms of fr 14 against the influenza virus. Fr 14 possessed antiviral and anti-inflammatory effects. L. pterodonta can be used to develop innovative antiviral drugs, and further studies will be performed to illustrate the detailed mechanisms.