Stercobilin hydrochloride (amixture of isomers) is a bile pigment metabolized by gut bacteria, and it's also an HIV protease inhibitor, with a K i of 4 μM. Stercobilin hydrochloride (a mixture of isomers) can induce pro-inflammatory activity in mouse macrophage RAW264 cells, including the production of TNF-α and IL-1β. Stercobilin hydrochloride (a mixture of isomers) can be used in studies of inflammation and viral infections.