Saponin: a class of chemical compounds, one of very many secondary metabolites found in natural sources, with saponins found in particular abundance in various plant species. Specifically, they are amphipathic glycosides grouped phenomenologically by the soap-like foaming they produce when shaken in aqueous solutions, and structurally by their being composed of one or more hydrophilic glycoside moieties combined with a lipophilic triterpene derivative (see Hostettmann & Marston 1995[1], and Cornell 2008[2]) (from Wikipedia) Click to read the wikepedia entry in full.