Berberine is a bitter-tasting, yellow, plant alkaloid with a long history of medicinal use in Chinese and Ayurvedic medicine. Berberine is present in the roots, rhizomes and stem bark of various plants including Hydrastis canadensis (goldenseal), Coptis chinensis (coptis or goldenthread), Berberis aquifolium (Oregon grape), Berberis vulgaris (barberry), and Berberis aristata (tree turmeric). Berberine has also been used historically as a dye, due to its yellow color. Clinical trials have been conducted using berberine. There is some evidence to support its use in the treatment of trachomas (eye infections), bacterial diarrhea, and leishmaniasis (parasitic disease). Berberine has also shown antimicrobial activity against bacteria, viruses, fungi, protozoans, helminths (worms), and chlamydia (STD). Future clinical research is warranted in these areas, as well as cardiovascular disease, skin disorders, and liver disorders. Berberine has been shown to be safe in the majority of clinical trials. However, there is a potential for interaction between berberine and many prescription medications, and berberine should not be used by pregnant or breastfeeding women, due to potential for adverse effects in the newborn.