In 1964 one group of investigators from the Pasteur Institute and the Paris Scientific Society concluded that Mate contains practically all of the vitamins necessary to sustain life. In addition to the regular nutrients, Mate contains a substance belonging to a specialized class of chemical compounds called xanthines. Though only small amounts of these substances occur in Mate, their presence has generated a huge amount of attention. The primary xanthine in Yerba Mate is called Mateine. The substance probably contributes little, if anything, to the overall activity of the plant, but has drawn a disproportionate share of speculation.
Some xanthines are obviously less desirable, such as caffeine.
Others, such as theophylline and theobromine, have specialized action and a characteristic set of side effects. Although the xanthines have similar chemistries, each has a unique set of properties. Mateine appears, then, to possess the best combination of xanthine properties possible. Likewise, unlike caffeine, it induces better, not worse, attributes of sleep. It is a mild, not a strong, diuretic, as are many xanthines.