Palmatine hydroxide is an orally active and irreversible indoleamine 2,3-dioxygenase 1 (IDO-1) inhibitor with IC 50 s of 3 μM and 157μM against HEK 293-hIDO-1 and rhIDO-1, respectively. Palmatine hydroxide can also inhibit West Nile virus (WNV) NS2B-NS3 protease in an uncompetitive manner with an IC 50 of 96 μM. Palmatine hydroxide shows anti-cancer, anti-oxidation, anti-inflammatory, neuroprotection, antibacterial , anti-viral activities.