Little research has been done on whole goldenseal root or rhizome, but many studies have evaluated the properties of its two primary alkaloids, berberine and hydrastine. Berberine, the more extensively researched of the two, accounts for 0.5–6.0% of the alkaloids present in goldenseal root and rhizome. However, the effect of goldenseal in the gastrointestinal tract is most likely localized as its alkaloids (particularly berberine) are poorly absorbed into the bloodstream, limiting any systemic antibiotic effects.² Goldenseal also has strong astringent properties which may partially explain its historical use for sore throats and diarrhoea. In test tube studies, it has shown a wide spectrum of antibiotic activity against disease-causing organisms, such as Chlamydia, E. coli, Salmonella typhi, and Entamoeba histolytica.³ Human trials have used isolated berberine to treat diarrhoea and gastroenteritis with good results.⁴ The whole root has not been clinically studied.