Yerba Mate: Chemistry, Technology, and Biological Properties

Purine Alkaloids

Xantines are a class of purine alkaloids found in many different plants, including tea, coffee and cocoa. The ones found in yerba mate include theophylline (1,3-dimethylxantine), theobromine (3,7-dimethylxantine) and caffeine (1,3,7-trimethylxantine). Of the three, caffeine is found in the highest concentration, 1-2% of dry weight, followed by theobromine, 0.3-0.9% of dry weight. Some authors have questioned the presence of theophylline in yerba mate for considering that this compound is just an intermediate in the catabolism of caffeine in the plant (Ito et al, 1977; Athayde et al, 2000; Schubert et al., 2006).

The concentration of caffeine in relation to consumer consumption has been found to be approximately 78 mg of caffeine in one cup of mate infusion, around 150 ml, a value near that of coffee. However, the customary rate of mate consumption prepared through the traditional method presents intakes above 500 ml, thus resulting in 260 mg or more of total caffeine (Mozzafera, 1997). It has also been suggested that the drying process can significantly affect caffeine concentration as well as color and chlorophyll content of leaves: up to 30% and 70-80% of caffeine and chlorophyll, respectively. However, even though caffeine concentration was lower in dried leaves than in fresh product, there is evidence that when the former was use to make the infusion, significantly more caffeine and caffeoylquinic acids were being extracted in comparison with fresh leaves. This increased extraction of compounds is likely from the disruption of cells during drying. It may also be explained by a decrease in moisture and an increase in soluble solids during drying, thus leading to a greater amount of compounds dissolved into the infusion (Barros et al, 2000; Schubert et al, 2006).