Palmatine hydroxide is an orally active, irreversible inhibitor of indoleamine 2,3-dioxygenase 1 (IDO-1), demonstrating IC50 values of 3 µM for HEK 293-hIDO-1 and 157µM for rhIDO-1. Additionally, it uncompetitively inhibits the West Nile virus (WNV) NS2B-NS3 protease with an IC50 of 96 µM. This compound exhibits a range of biological activities, including anti-cancer, anti-oxidation, anti-inflammatory, neuroprotective, antibacterial, and antiviral effects.