saponin

plural saponins

1. biochemistryAny of various steroid glycosides found in plant tissues that dissolve in water to give a soapy froth.

   “Saponins aren't absorbed by the intestines. You've got to get the stuff into the blood.”

   1985, Wade Davis, The Serpent and the Rainbow, Simon & Schuster, page 111

   1 more example

   Soapnuts are the dried fruit of a tree called Sapindus mukorossi (Chinese Soapberry) and contain saponin, a natural surfactant that foams just like soap.

   2015, Beth Terry, Plastic-Free: How I Kicked the Plastic Habit and How You Can Too, Simon and Schuster, →ISBN