Sanguinarine is a polycyclic quaternary alkaloid. It is extracted from some plants, including the bloodroot plant, from whose scientific name, Sanguinaria canadensis, its name is derived; the Mexican prickly poppy ; Chelidonium majus; and Macleaya cordata.

Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure may also be termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen or sulfur. More rarely still, they may contain elements such as phosphorus, chlorine, and bromine.