Yerba mate or yerba-mate (Br.) (Spanish: yerba mate, Portuguese: erva-mate), Ilex paraguariensis, is a species of holly (family Aquifoliaceae) native to subtropical South America in northeastern Argentina, eastern Paraguay and southern Brazil. Mate contains xanthines, which are alkaloids such as caffeine, theophylline, and theobromine, well-known stimulants also found in coffee and chocolate.
Caffeine content varies between 0.2% and 2% of dry weight (compared with 0.3–9% for tea leaves, 2.5-7.5% in guarana, and up to 3.2% for ground coffee). However, caffeine is not chiral, and thus cannot have a stereoisomer, and "mateine" is an official synonym of caffeine in the chemical databases.
Mate also contains elements such as potassium, magnesium and manganese. In vivo and in vitro studies are showing yerba mate to exhibit significant cancer-fighting activity. Researchers at the University of Illinois (2005) found yerba mate to be "rich in phenolic constituents" and to "inhibit oral cancer cell proliferation" while it promoted proliferation of oral cancer cell lines at certain concentrations.