saponin

sa·po·nin

noun \ˈsap-ə-nən, sə-ˈpō-\

Definition of SAPONIN

: any of various mostly toxic glucosides that occur in plants (as soapbark) and are characterized by the property of producing a soapy lather; especially : a hygroscopic amorphous saponin mixture used especially as a foaming and emulsifying agent and detergent