Saponins are a vast group of glycosides widely distributed in higher plants which are distinguishable from other glycosides by their surface active properties. They dissolve in water to form colloidal solutions that foam upon shaking. The biological applications of saponins are usually based on their membrane-disrupting properties, and formation of large mixed micelles with steroids and bile acids. They are believed to form the mains constituents of many plants drugs and folk medicines, and are considered responsible for numerous pharmacological properties. For example, the ginseng (Panax ginseng) root, one of the most important medicinal oriental products used worldwide, has saponins as the major bioactive constituents.
The leaves of I. paraguariensis contain a significant amount of triterpenoid saponins. Monodesmosidic and bidesmosidic saponins have been isolated from the aerial parts of yerba maté, and all compounds contained the ursolic or oleanolic moieties.
Saponins may be used as a chemical fingerprint for the authentication of yerba maté. Adulteration by variable quantities of leaves of other South American Ilex species, showing complete different saponin profile from yerba maté, is rather common.
Gosamnn and Schenkel reported the isolation and elucidation of a new saponin, named matesaponin, from the leaves of yerba maté which is a three sugar residue bidesmoside.
The triterpenoids ursolic acid and its isomer, oleanolic acid, are compounds found widely in the plant kingdom that have many biological effects: anti-inflammatory, antiarthritic, and antitumor activity, hepatoprotective effects in mice, and membrane-stabilizing properties.
Saponins are reported to interfere with cholesterol metabolism and to delay the intestinal absorption of dietary fat via inhibition of pancreatic lipase activity.
Caffeine, saponins and phenolic contents are one of the main targets for yerba maté genetic improvement due to their role in the bitter and astringent attributes of the beverages.