Saponin

Any of a group of glycosides obtained from plants that gives a soapy lather with water. Saponin is obtained from several unrelated species, including the bark of the soap bark tree, the roots of the soap plant, the fruit of the soapberry tree, and the leaves of the soapwort plant. Saponins have been used since ancient times as a natural cleaner. Uses include in solution as a mild detergent for cleaning dirt and smoke from paintings. It is poisonous to fish or if injected into the bloodstream.