Goldenseal is a perennial herb. It's native to eastern North America. The roots and rhizome are the parts that are used.
Goldenseal contains the alkaloids hydrastine and berberine. These have weak antiseptic effects. They may help fight bacteria-induced diarrhea. You shouldn't take goldenseal during pregnancy. This is because it may cause uterine contractions.
In the past, goldenseal was used by Native Americans to treat sore eyes, mouth ulcers, tuberculosis, and edema. Now there's evidence that berberine works against resistant strains of tuberculosis. But berberine isn't used as a primary or add-on treatment for tuberculosis. Berberine may also work well to control blood sugar in people with diabetes. If you have diabetes, don't take goldenseal or berberine without talking with your doctor first.
Goldenseal has also been used in eyedrops. It's used on tired, burning, red, and irritated eyes.