Identification of a Novel Alkaloid Zj6-11 as a Potent Inhibitor of Influenza Virus Infection via Repression of Virus-Induced Mitochondria-Dependent Apoptosis.

Influenza A virus (IAV) remains a major global public health threat, especially with the emergence of antiviral resistance, highlighting the urgent need for novel therapeutics. Alkaloids are known for their antiviral properties, and chemical synthesis has become a key strategy in developing new alkaloid compounds. In this study, we synthesized a series of novel alkaloids using the Ugi reaction and assessed their antiviral potential and mechanisms. Through screening and validation, Zj6-11 was identified as a promising compound that effectively inhibits IAV infection in vitro. Molecular docking and binding affinity assays showed that Zj6-11 binds with high affinity to IAV nucleoprotein (NP) and inhibits its interaction with nucleic acids. Further, in vitro nuclear translocation assays confirmed that Zj6-11 suppresses NP nuclear import. Mechanistically, Zj6-11 significantly inhibits IAV-induced apoptosis and mitigates mitochondrial membrane potential dysfunction. Zj6-11 also inhibits cytochrome c release, reduces the expression of cleaved Caspase-9 and Caspase-3, and suppresses IAV-induced apoptosis-inducing factor (Aif) expression, suppressing IAV-induced mitochondrial apoptosis. More importantly, Zj6-11 plays a crucial role in protecting mice from IAV infection and reducing IAV pathogenicity. Our study provides mechanistic insights into Zj6-11's control of IAV infection in vitro and in vivo, offering new perspectives for antiviral therapy development.