Berberine is an isoquinoline alkaloid with a bright yellow color that is easily seen in most of the herb materials that contain any significant amount of this compound.
Several Western herbs also contain berberine, such as barberry root bark (Berberis vulgaris), Oregon grape root (Berberis aquifolium), and goldenseal root (Hydrastis canadensis). Primary Chinese sources are phellodendron and coptis.
Berberine has long been used as a dye; it is currently known as "natural yellow 18."
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