Yerba Mate, in Spanish, or chimarrão in Brazilian, is a non-alcoholic beverage that in South America has been consumed for centuries and that now is gaining popularity also outside its original land thanks to its beneficial properties on health and its stimulating activity.
Yerba Mate, also known as Paraguayan tea, is obtained from the leaves of the tree Ilex paraguariensis, a member of the South American family of Aquifoliaceae. Guarani people, living around the Paraguay River basin, are reported to be the first consumers of the tea and they considered the plant a gift from Mother Earth.[1] Later on, Jesuits who colonized those lands around 1670 appreciated this beverage’s properties and started to cultivate the tree professionally. When the order was dissolved, the plantations were abandoned and became wild until the 20th century, when the difficult art of cultivating this plant was recovered. [2]
Ilex paraguariensis tree is found in the North of Argentina, which is the first producer of Yerba Mate, Uruguay, Paraguay, and South of Brazil. The production of Yerba Mate is estimated to be 1.4 million tons per year of which only 5% is exported.[2] The plant cultivation is not easy: it has been attempted in other countries with a similar climate with unsuccessful results.[1] Indeed, Ilex paraguariensis can bear temperatures as low as -6 °C but needs high humidity with rain-falls not under 1200 mm.[3]
The beverage commonly called mate, owes its name to its jar. The word “mate” comes from matì, which in Quechua means “herbs from the calabash” because the original vessel was made from calabash fruit.[2] Dry leaves are put in the bottom of the mate, water – hot or cold – is poured on top, and the beverage is assumed through a bombilla, a straw with a filter that avoids the leaves and the powder to pass. Since leaves can be reused multiple times by adding some water, without the need for any stove or special machine, people drink the brew at any moment of the day, even while walking. Indeed, 30% of South America’s population drinks more than 1L of mate per day.[1]
To make Yerba Mate, 6 to 12 month old leaves are harvested, roasted, and dried. Afterward, they must undergo a period of maturation – at least 12 months – that determines the typical flavor of the brew, followed by a last sieving step. Indeed, the leaves/twigs ratio is different in each Yerba Mate variety and contributes to the quality of the beverage.[2]
Chemical Composition
Yerba Mate dry leaves contain around 200 chemical compounds including some that are highly interesting from a pharmaceutical and/or nutraceutical point. Among all substances that can be extracted from Ilex paraguariensis’s leaves some classes of molecules benefit of a larger attention from researchers thanks to their biological activity.
- Polyphenols are among the most studied compounds because of their antioxidant activity. They can be found in many widely consumed foods and drinks. Among these, both green tea and mate are well-known for their antioxidant power due to their high polyphenol content (around 50 µg per mg of dry biomass).[2][3]
However, mate composition- regarding polyphenols – differs from both green and black tea, being rich of chlorogenic acid, the dominant compound belonging to this class, and showing no presence of catechins, which are the major responsible for antioxidant activity in tea.[3] Furthermore, polyphenols content in Yerba Mate can vary with plant exposition to the sun. Indeed, it’s been found that raw materials from sunny plantations were the richest in polyphenols.[2] Among important polyphenols present in Ilex paraguariensis there are the flavonoids rutin and quercetin, important for their antimicrobial and antioxidant activity.[1]
- Xanthines are a class of purine alkaloids that are present in worldwide consumed foods and beverages in addition to yerba mate, such as coffee, tea, and chocolate. The most famous xanthine is caffeine, to which the majority of these products owe their success thanks to its stimulating effect.
Yerba Mate presents a significant amount of caffeine (1-2% of dry weight) as long as other methylxanthines such as theobromine and theophylline. The caffeine content in a cup of Mate tea is comparable to that contained in a cup of coffee (around 80 mg), however, since it is possible to brew it multiple times, the final intake is much higher.[3] Furthermore, caffeine concentration in the tea is higher with increasing brewing time and temperature.[2]
- Saponins are responsible for the typical bitter taste of mate. They are a water-soluble class of molecules, and triterpene saponins, deriving from ursolic and oleanolic acids, can be found in Yerba Mate.[3]
Other significant components of Yerba Mate are linolenic acids and minerals, both important for a balanced and healthy diet. The first ones can represent a source of supplementation of polyunsaturated fatty acids, while minerals are involved in a lot of human metabolic processes. However, inorganic compounds’ content strongly varies with factors such as soil, weather, and raw material processing.[1][3]
Healing Properties
As previously said, mate owes its success largely to its stimulating activity. Caffeine, indeed, not only stimulates the central nervous system (CNS) but also the heart and muscles, having a significant effect on several functions such as alertness, concentration, mental and physical fatigue, feeling of satiety, thermogenesis, and fat oxidation. An excessive consumption of caffeine (0.5 – 1.5 g per day), however, can cause gastrointestinal upset, increasing heart rate, giving the feeling of anxiety and nervousness.
Even though, as previously said, daily assumption of caffeine from mate can be much more than for coffee, regular Yerba Mate consumers admit that the brew gives them energy, without causing that sense of nervousness that is often registered after drinking a cup of coffee.[1][2]
From a pharmacological point of view, mate has been mainly studied for its antioxidant activity, comparable to that of green tea.[3] Both DPPH radical scavenging radicals and catalase activity assays were used to test in vitro Yerba Mate’s antioxidant activity, which is related to its polyphenol content.[2] A good antioxidant power has a crucial effect on cardiovascular diseases.
Many clinical trials have also been carried out, focusing the attention on lipid peroxidation, and, in particular, on low density lipoprotein (LDL), also known as “bad cholesterol” since it has a key role in the onset of atherosclerosis. Consumption of Yerba Mate has also been associated with higher expression of antioxidant genes.[4] Furthermore, there are studies on Yerba Mate modulating perimenopausal oxidative stress and reducing the occurrence of common cardiovascular diseases in post-menopausal women.[2]
Mate has also shown antidiabetic properties due to the combination of antioxidant and antiglycation effects. It has been proven that the consumption of Yerba Mate has a positive effect on serum lipid parameters in normolipidemic, dyslipidemic, prediabetic and type II diabetic subjects. At the same time, mate reduces the production of advanced glycation end products (AGEs).[4]
Finally, mate has been studied for its weight loss potential. Indeed, mate shows high thermogenic power, without influencing heart rate and blood pressure, that is often a limitation in the use of sympathomimetic drugs as anti obesity thermogenic agents.[5] The best effects on weight loss have been reported when the consumption of mate is accompanied with low-intensity physical exercise. Indeed, mate increases the oxidation of fatty acids, which are the fuel for light and moderate exercises, while reducing the oxidation of carbohydrates, that are mainly burnt during high-intensity exercises.[4]
Different Extractions for Different Molecules
Even though mate tea has proven to be beneficial to consumers, home brewing could not be the most efficient way to assume bioactive compounds contained in mate, since their extraction could be partial.[4] To use mate in pharmaceutical preparations, extraction methods have to be optimized. As already discussed, Yerba Mate contains several compounds, which have different physicochemical properties and thus require different extraction techniques.
The main observation about Yerba Mate extraction is that best recovery yields of polyphenols and xanthines have been found using at least 50% of organic solvent (acetone, methanol, or DMF).[3][6] The use of organic solvents, however, could be troublesome for further nutraceutical applications. These results have been obtained both for traditional extraction methods such as maceration and solvent extraction, and for more recent ones such as ultrasound-assisted extraction. This last method, even though allows to obtain high yields of different compounds, is also affected by high extraction time and solvent-to-sample mass ratio.[3]
A promising method to obtain high yields of xanthines is using supercritical CO2. This method not only allows to reach much higher concentrations than with other methods, but it is a “green” extraction method and doesn’t imply any drawbacks for human health.[3]
The coupling of pressurized liquid extraction (PLE) and solid-phase extraction (SPE) with an UV-detector has turned out to be a successful way to simultaneously extract and separate compounds from dry leaves. In this case, water solutions with different ethanol ratios have been employed. These solvents are considered to be green and harmless, which is positive for nutraceutical applications. Even though this method has shown similar compounds recovery to other methods, a significant difference was reported regarding flavonoids.[7]
The Dark Side of Mate
The last aspect that has to be mentioned about mate is that an increase in cancer occurrence, particularly of the esophagus, has been registered among mate drinkers. However, in these studies, several factors such as smoking or drinking alcohol, besides drinking mate, have been neglected and it’s hard to attribute the whole responsibility to mate. Furthermore, carcinogenicity is probably not a characteristic of mate itself, but of incidental events.[2][3] Indeed, it has been proven that consuming hot beverages increases the probability of developing some cancers, namely, esophageal, oral, bladder, lung, and renal. It is interesting to note that drinking cold mate tea also induces greater stimulation of thermogenesis and fat oxidation than hot tea, thanks to the simultaneous increase of adrenaline (induced by caffeine) and noradrenaline (induced by cold exposure) plasmatic concentration.[5]
In addition, the incidence of such diseases has also been attributed to the ingestion of toxic polycyclic aromatic hydrocarbons (PAHs). These compounds are not proper of Yerba Mate but can accumulate in it due to soil and atmosphere contamination.[2] It is also highly probable that PAHs are produced during mate processing, which traditionally involves drying the leaves over a smoky wood fire. In the end, PAHs can also be assumed through cigarettes, thus representing again a confounding factor.[3]
Apart from this supposed carcinogenicity, that depends on conditions that can be easily controlled and avoided, it is not difficult to understand why the regard that Guarani people addressed to Ilex paraguariensis has survived to date. Yerba Mate has been proven to be beneficial not only when home brewed, but also in nutraceutical preparations to treat chronic diseases such as atherosclerosis, diabetes, and obesity.
References:
(1) Lutomski, P.; Goździewska, M.; Florek-łuszczki, M. Health Properties of Yerba Mate. Annals of Agricultural and Environmental Medicine 2020, 27 (2), 310–313. https://doi.org/10.26444/aaem/119994.
(2) Gawron-Gzella, A.; Chanaj-Kaczmarek, J.; Cielecka-Piontek, J. Yerba Mate—a Long but Current History. Nutrients. MDPI November 1, 2021. https://doi.org/10.3390/nu13113706.
(3) Heck, C. I.; De Mejia, E. G. Yerba Mate Tea (Ilex Paraguariensis): A Comprehensive Review on Chemistry, Health Implications, and Technological Considerations. Journal of Food Science. November 2007. https://doi.org/10.1111/j.1750-3841.2007.00535.x.
(4) Riachi, L. G.; De Maria, C. A. B. Yerba Mate: An Overview of Physiological Effects in Humans. Journal of Functional Foods. Elsevier Ltd November 1, 2017, pp 308–320. https://doi.org/10.1016/j.jff.2017.09.020.
(5) Maufrais, C.; Sarafian, D.; Dulloo, A.; Montani, J. P. Cardiovascular and Metabolic Responses to the Ingestion of Caffeinated Herbal Tea: Drink It Hot or Cold? Front Physiol 2018, 9 (APR). https://doi.org/10.3389/fphys.2018.00315.
(6) Turkmen, N.; Sari, F.; Velioglu, Y. S. Effects of Extraction Solvents on Concentration and Antioxidant Activity of Black and Black Mate Tea Polyphenols Determined by Ferrous Tartrate and Folin-Ciocalteu Methods. Food Chem 2006, 99 (4), 835–841. https://doi.org/10.1016/j.foodchem.2005.08.034.
(7) Souza, M. C.; Silva, L. C.; Chaves, J. O.; Salvador, M. P.; Sanches, V. L.; da Cunha, D. T.; Foster Carneiro, T.; Rostagno, M. A. Simultaneous Extraction and Separation of Compounds from Mate (Ilex Paraguariensis) Leaves by Pressurized Liquid Extraction Coupled with Solid-Phase Extraction and in-Line UV Detection. Food Chemistry: Molecular Sciences 2021, 2. https://doi.org/10.1016/j.fochms.2020.100008.
