Sanguinarine is a toxic polycyclic quaternary ammonium salt. It is extracted from some plants, including bloodroot (Sanguinaria canadensis), Mexican prickly poppy Argemone mexicana, Chelidonium majus and Macleaya cordata. Sanguinarine is a toxin that kills animal cells through its action on the Na+-K+-ATPase transmembrane protein. If applied to the skin, sanguinarine may cause a massive scab of dead flesh, called an eschar. For this reason, sanguinarine is termed an escharotic. Preliminary pre-clinical in vitro and in vivo studies have demonstrated that sanguinarine causes apoptosis in human cancer cells, and recommend study of sanguinarine as a potential cancer treatment. Sanguinarine has been the subject of other medical fields as well. For instance, it has garnered interest as a chemical defense against microorganisms and viruses. Notably, experiments on human plaque accumulation in the presence of sanguinarine suggest the toxin may be effective against oral microbial isolates. However, no products containing sanguinarine are currently approved by the FDA for the treatment of cancer; the FDA warns that unapproved bloodroot preparations are ineffective and dangerous.