Powdered root and rhizome (underground stem) are used to make extracts, tablets and capsules.
The roots are bright yellow with distinctive scars, giving it its name.
It is an endangered plant in the wild, so supplies must come only from cultivated plants.
Goldenseal has antibiotic activity that is made use of externally for fungal infections and minor wounds, and internally against bacteria that cause ulcers and diarrhoea.
The active chemical in the plant, called berberine, is not well absorbed into the blood, so its use is limited to areas that are easily accessed, the skin, mouth and throat, and gastrointestinal tract.
Goldenseal is usually combined with Echinacea in popular cold and flu remedies. It is more effective when used along with other herbs.
Accepted doses are 250 to 500 milligrams of standardised extract taken three times a day, preferably in liquid form. (Capsules do not work so efficiently.)
Ideally it should only be taken for two weeks at any one time. There should be a minimum gap of two weeks before resuming treatment, if that is necessary.
Goldenseal is very expensive due to its rarity and cost of production. A cheaper alternative is Oregon grape root, which also contains berberine, but is thought to be less effective.
Normal doses are very safe, but very large doses can cause gastric upset.
Do not take Goldenseal if you are pregnant or if you have heart problems as it can cause uterine contractions and raise blood pressure