Herquline A (CAS: 71812-08-3)

Herquline A is a pentacyclic piperazine alkaloid produced by Penicillium herquei. Originally identified as a weak inhibitor of ADP-induced platelet aggregation, it was later shown to inhibit replication of influenza A virus (A/PR/8/34 strain) in a dose-dependent manner without significant cytotoxicity. Mechanistic studies indicate that herquline A does not inhibit viral neuraminidase, suggesting a distinct antiviral target within the viral replication cycle. Herquline A represents one of the earliest characterized fungal piperazine alkaloids and serves as a structural prototype within this alkaloid class.