Barberry (also known as jaundice berry, pepperidge, or sowberry) is a heavily branched, perennial, deciduous, thorny shrub native to temperate regions of Europe, Asia, and northern Africa. Growing up to 2 meters in height, the stem of the mature plant is covered with gray bark, with three sharp spines at the joint of each branch. The leaves are ovate, 2 to 4 centimeters long, with four or five leaves on each branch. Barberry flowers in spring, bearing dense, hanging clusters of yellow blossoms, which eventually produce ovoid, orange-red berries, 10 to 12 millimeters long and 6 millimeters thick. The berries and the dried root bark are used for health purposes.
The primary constituents in barberry root bark are a group of alkaloid compounds, which includes berberine, jatrorrhizine, berberubine, berbamine, bervulcine, palmatine, columbamine, and oxyacanthine. The root also contains chelidonic, citric, malic, and tartaric acids. Of all the compounds found in barberry, berberine, which is also found in goldenseal, goldenthread, and Oregon grape, has been the most extensively researched.
Dosage recommendations for barberry vary with the type of preparation and the intended application. A typical daily dosage recommendation is 2 grams of the bark prepared as an infusion with 250 milliliters of water. No health hazards or side effects are associated with the herb at this dosage range. Although berberine has low toxicity and is well tolerated at intakes up to 500 mg per day, berberine intakes over 500 mg may cause side effects such as lethargy, nose bleed, breathing difficulties, skin and eye irritation, and kidney irritation. Gastrointestinal disturbances with nausea, vomiting, and diarrhea have also been reported.