Saponin
Saponins are a class of chemical compounds, one of many secondary metabolites found in natural sources, with saponins found in particular abundance in various plant species. More specifically, they are amphipathic glycosides grouped, in terms of phenomenology, by the soap-like foaming they produce when shaken in aqueous solutions, and, in terms of structure, by their composition of one or more hydrophilic glycoside moieties combined with a lipophilic triterpene derivative.
Read more about Saponin: Structural Variety and Biosynthesis, Sources, Role in Plant Ecology and Impact On Animal Foraging, Ethnobotany