Palmatine chloride is an orally active and irreversible indoleamine 2,3-dioxygenase 1 (IDO-1) inhibitor. Palmatine chloride can ameliorate DSS-induced colitis by mitigating colonic injury, preventing gut microbiota dysbiosis, and regulating tryptophan catabolism. Palmatine has the potential for colitis treatment^[1]. In Vitro: Palmatine exhibits more potent IDO-1 inhibitory activity , which IC₅₀ on rhIDO-1 is 157 μM, and on HEK 293-hIDO-1 is 3 μM^[1]. In Vivo: Palmatine (oral administration; 50 or 100 mg/kg, 7 days) has less distortion of epithelium, and fewer infiltrations of inflammatory cells, resulting in significantly lower histopathological scores, it also significantly suppresses the colonic MPO activity^[1].