Alkaloids, including berberine, berbamine, canadine, and hydrastine, may account for the activity of Oregon grape. Isolated berberine has been shown to effectively treat diarrhea in patients infected with E. coli. One of the ways berberine may ease diarrhea is by slowing the transit time in the intestine. Berberine inhibits the ability of bacteria to attach to human cells, which helps prevent infections, particularly in the throat, intestines, and urinary tract. These actions, coupled with berberine’s ability to enhance immune cell function, make Oregon grape possibly useful for mild infections although clinical trials are lacking on the whole root.
In one clinical trial, an ointment of Oregon grape was found to be mildly effective for reducing skin irritation, inflammation and itching in people with mild to moderate psoriasis. Whole Oregon grape extracts were shown in one pharmacological study to reduce inflammation (often associated with psoriasis) and stimulate the white blood cells known as macrophages. In this study, isolated alkaloids from Oregon grape did not have these actions. This suggests that something besides alkaloids are important to the properties of Oregon grape responsible for reducing inflammation.
The bitter-tasting compounds as well as the alkaloids in Oregon grape root are thought to stimulate digestive function.