Yerba Mate Tea (Ilex paraguariensis)

a comprehensive review of chemistry, health implications, and technological considerations

The content on this page comes from International Journal of Food Science and has been translated into Polish.

Link to source – https://ift.onlinelibrary.wiley.com/doi/full/10.1111/j.1750-3841.2007.00535.x?vis=107973391.14074560005139_

Abstract

SUMMARY: Yerba Mate tea, an infusion of the leaves of the Ilex paraguariensis tree, is a widely consumed non-alcoholic beverage in South America that is rapidly gaining popularity on the global market, both as a tea on its own and as an ingredient in ready-made food products or dietary supplements. Indigenous peoples have used it for centuries as a social and medicinal drink. Yerba Mate has been shown to have hypocholesterolemic, hepatoprotective, central nervous system-stimulating, diuretic and cardiovascular-beneficial effects. It has also been suggested for the treatment of obesity. Yerba Mate protects DNA from oxidation and in vitro peroxidation of low-density lipoproteins and has a high antioxidant capacity. Yerba Mate tea has also been reported to be linked to both the prevention and the cause of certain types of cancer. Yerba Mate has gained public interest outside of South America, namely in the United States and Europe, and research on this tea is expanding. This review presents the use, chemistry, biological activity, health effects and some technological considerations regarding the processing of Yerba Mate tea. Furthermore, it assesses, in a concise and comprehensive manner, the potential of Ilex paraguariensis as a source of biological compounds for the nutraceutical industry.

Introduction

Yerba Mate tea (Mate), a herbal tea beverage commonly consumed in the countries of southern Latin America (southern Brazil, Argentina, Paraguay and Uruguay), is rapidly gaining ground in global markets, including the United States. It is obtained from an infusion of the dried leaves of Ilex paraguariensis , a plant from the Aquifoliaceae family ( Small and Catling 2001 ; Grigioni et al. 2004). In Latin America, Mate is often drunk from a dried gourd through a metal straw called a “bombilla”. Dried leaves (about 50 g) are placed in the gourd and covered with hot water; this is then repeated many times, with amounts ranging from half a litre to 1 litre of water. However, in the United States, Mate is commercially packaged in individual tea bags (1 to 2 g) or as a Mate tea concentrate for use as an ingredient in the food industry or dietary supplements. Given the importance of the growing consumption of Mate tea and products containing Mate tea, the aim of this review is to gather and comprehensively analyse the current scientific information on Yerba Mate, including its composition, physiological effects and potential health effects. Furthermore, this review aims to further stimulate the use of Yerba Mate as a nutraceutical ingredient.

Mate tea has recently received a lot of attention for its health benefits, but concerns have also been raised about its safety. The scientific literature, on one hand, reports that Mate tea is hypocholesterolemic and hepatoprotective ( Filip and Ferraro 2003 ), stimulates the central nervous system, is diuretic ( Gonzalez et al. 1993 ), and has antioxidant properties ( Filip et al. 2000 ; VanderJagt et al. 2002 ). It also has a beneficial effect on the cardiovascular system ( Schinella et al. 2005 ), protects against DNA oxidation and lipoperoxidation of low-density lipoproteins (LDL) in vitro ( Bracesco et al. 2003 )). Some studies also suggest its potential in the treatment of obesity ( Andersen and Fogh 2001 ; Pittler and Ernst 2004 ; Opala et al. 2006 ). Many active phytochemicals have been identified in Mate tea that may be responsible for its health benefits. Among them, the 2 highest compounds are polyphenols (chlorogenic acid) and xanthines (caffeine and theobromine), followed by purine alkaloids (caffeic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid), flavonoids (quercetin, kaempferol and rutin), amino acids, minerals (P, Fe and Ca), and vitamins (C, B1 and B2) ( Pomilio et al. 2002 ; Zaporozhets et al. 2004). Mate tea has been shown not only to contain high concentrations of bioactive compounds, but also to exhibit cytotoxic effects on human hepatoma cells (HepG2) and may act as a catalytic inhibitor of topoisomerase II ( Ramirez-Mares et al. 2004 ) . .

On the other hand, some epidemiological studies have shown a link between Mate tea consumption and an increased risk of various types of cancer, including cancer of the mouth, oral cavity and pharynx, esophagus, larynx and bladder ( Goldenberg et al. 2003 ; Sewram et al. 2003 ; Bates et al. 2007 ).

Ethnobotany and Botanical Description

Ilex paraguariensis , from the sacred plant family Aquifoliaceae, is a native South American tree used to produce Yerba Mate tea. It occurs mainly in the southern regions of South America, namely in Brazil (Mato Grosso do Sul, Minas Gerais, Parana, Rio Grande do Sul, Rio de Janeiro, Santa Catarina, Sao Paulo), Argentina (Corrientes, Misiones), Paraguay (Alto Parana, Amambay, Caaguazu, Canendiyu, Central, Guaira, Itapua, Misiones, San Pedro) and Uruguay ( USDA, ARS, National Genetic Resources Program 2007 ). Figure 1Ashows the main regions where Mate is cultivated. Among these regions, the largest producer is Argentina, growing about 152,000 hectares of Mate annually in the northeastern part of the country (Misiones and Corrientes). This corresponds to about 280,000 tons per year, which accounts for a large part of the countries’ gross domestic product. Brazil and Paraguay are the second and third largest producers, respectively. Worldwide, in 2002, 290,000 ha of harvested area were reported, producing 874,678 tons of Mate ( FAOSTAT 2007 ). The overall value of Mate production worldwide was estimated at 1 billion USD in 2004.

Details in the image caption — **Figure 1—**Open in figure viewer PowerPoint **(A) Map of South America showing the growing regions of Yerba Mate *(Ilex paraguariensis)* 1 Argentina; 2 Brazil, 3 Paraguay, 4 Uruguay. (B) The Yerba Mate plant.**

Ilex paraguariensis is a subtropical, dioecious, evergreen tree that can reach 18 m in height. Figure 1B shows a photo of the Mate plant. The Mate tree is a flowering and fruiting plant, blooming from October to November and fruiting from March to June. The Mate plant requires a strict annual rainfall regime, both in amount, not less than 1200 mm, and in distribution throughout the year. However, it is much less sensitive to temperature, withstanding temperatures down to -6°C, with an average annual temperature of 21 to 22°C. It is also able to withstand frequent snowfalls, which are attributed to the mountainous region in which it lives.

Cultivation and harvesting of Mate is not a uniform procedure and is carried out using different methods depending on the region. The three basic methods of cultivation and harvesting are exploitation of natural forests, mixed systems, and cultivated Mate plantations. Exploitation of natural forest involves wild harvesting of mate from the forest and is the least consistent of the 3 methods in terms of quality and quantity. The second method, the mixed system, combines forest growth with improved cultivation practices, including replanting lost plants and improved pruning methods. This practice ensures a better production rate when growing natural forest products. Both natural forest harvesting and mixed-system cultivation occur mainly in Brazil. Cultivated Mate plantations,Giberti 1994 ).

Processing of Yerba Mate tea

Yerba Mate is not consumed in its raw form, but is processed before it reaches the consumer. Fresh Mate leaves go through several processing stages before being packaged. This includes blanching, drying and general ageing of the tea. Processing conditions vary greatly depending on the producer and the final goal of achieving the desired style and flavour of Mate tea. Processors may vary the blanching and drying time and temperature. Not all producers age the tea, while others vary the ageing time ( Bastos et al. 2006a ). However, the overall process is essentially the same. Figure 2A shows a typical process flow chart for Mate tea.

Mate undergoes very slight fermentation and a blanching process that deactivates enzymes, namely polyphenol oxidase. The difference in the blanching process, however, is that green tea leaves are steamed or pan-fried, while Mate tea leaves are quickly heated over an open flame. This blanching process differs from the one used in black tea production; black tea leaves are left to wither and ferment and are not blanched before drying. Figure 2B shows the production process for green and black tea. In black tea, the enzyme polyphenol oxidase can oxidize polyphenols, forming dimerized compounds, namely catechins into theaflavins ( Hara 2001 ).

The main difference between green tea and Mate tea production is the drying method. Green tea is dried primarily through rapid high-temperature air-drying, which preserves more of the fresh leaf characteristics and also develops distinctive flavour and aroma compounds. Mate tea is dried very slowly and often using wood smoke. This gives it very different flavour properties and contributes to changes in chemical composition and physical appearance. Another important difference between Mate and green tea is the presence of stems in the final product. Green tea production removes all large stems before grinding ( Graham 1992 ); however, Mate will generally contain a high content of stem pieces, depending on the producer.

Phytochemistry

Polyphenols

Polyphenols are a class of compounds containing a benzene ring bound to one or more hydroxyl groups. These compounds have been analyzed using several methods, including the tyrosinase biosensor, the Folin Ciocalteu assay, and high-performance liquid chromatography (HPLC) ( Carini et al. 1998 ; Chandra and De Mejia Gonzalez 2004 ; Dall’Orto 2005 ). These analyses have shown that the Mate variety, the degree of grinding, and blending with other teas determine the concentration of polyphenols extracted in the infusion. On average, the amount of polyphenols extracted from Mate tea is 92 mg chlorogenic acid equivalent per gram of dry leaves, with blended teas having significantly less ( Dall’Orto 2005). The polyphenol concentration in mate also showed a strong correlation with its overall antioxidant capacity ( Chandra and De Mejia Gonzalez 2004 ). Mate showed a slightly higher polyphenol concentration, 7.73 ± 0.15 mg chlorogenic acid/mL of aqueous extract, than green tea, 7.15 ± 0.14 mg chlorogenic acid/mL of aqueous extract. This correlates with the higher antioxidant capacity of Mate, 90.45 ± 0.22% free radical inhibition, than green tea, 88.36 ± 0.76% free radical inhibition, when the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method was used ( Bastos et al. 2007 ). Furthermore, the amount of polyphenols extracted from Mate is affected by the extraction method used, i.e. water or organic solvent, with 50% acetone extraction yielding the greatest amount of polyphenols (Turkmeni et al. 2006 ).

The polyphenolic compounds found in Mate tea differ significantly from those in green tea, as Mate tea contains a high concentration of chlorogenic acid and does not contain catechins ( Chandra and De Mejia Gonzalez 2004 ). Table 1 shows the variety of polyphenolic compounds in green tea, black tea, and Mate tea. Table 1-. Polyphenols in green tea, black tea, and Mate tea. ^a

	Green Tea	Black Tea	Mate Tea
Caffeic acid	•		•
Caffeine	•	•	•
Caffeine derivatives			•
Caffeoylshikimic acid			•
Catechin	•	•
Catechin gallate		•
Chlorogenic acid			•
Coumaric acid	•
Epicatechin gallate	•	•
epigallokatechina	•
Epigallocatechin gallate	•
Feruloylquinic acid			•
Gallic acid	•	•
Gallocatechin gallate	•	•
kemferol	•	•	•
mirycetyna	•	•
Procyanidin		•
kwercetyna	•	•	•
Quinic acid	•		•
Rutin	•	•	•
Theaflavin		•
Theobromine		•	•

^{a Based on} Carini et al. (1998) ; Chandra and de Mejia Gonzalez (2004) ; Atoui et al. (2005) ; Bastos et al. (2007) ; Bravo et al. (2007) .

ksantyny

Xanthines are a class of purine alkaloids found in many different plants, including tea, coffee, and chocolate. The xanthines present in Mate are theophylline (1,3-dimethylxanthine), theobromine (3,7-dimethylxanthine), and caffeine (1,3,7-trimethylxanthine) ( Athayde et al. 2000 ). The structural formulas of these compounds are shown in Figure 3 . Of these three, caffeine occurs at the highest concentration, 1% to 2% of dry matter, followed by theobromine, 0.3% to 0.9% of dry matter ( Ito et al. 1997). These 2 compounds are found mainly in the plant’s leaves and in smaller concentrations in the woody stems that are often present in the product, as well as in the epicuticular waxes of the leaves (0.5% of wax content in leaf dry matter), with 5.9 to 17.0 ng of caffeine per milligram of wax and 0.9 to 3.5 ng of theobromine per milligram of wax ( Athayde et al. 2000 ), although the main amounts of these methylxanthines are found inside the leaves.

The caffeine concentration relative to consumer intake was found to be about 78 mg of caffeine in 1 cup of Mate tea (about 150 ml). Compared to coffee, this is a very similar amount of caffeine intake, about 85 mg per cup. However, a customary serving of mate prepared in the traditional way may represent an intake of about 500 ml, which gives 260 mg or more of total caffeine ( Mazzafera 1997 ).

Unlike theobromine and caffeine, theophylline has been found in the leaves only in small amounts. This may be due to the fact that theophylline appears to be an intermediate in the catabolism of caffeine in the plant. It is believed that the main pathway of theophylline metabolism is conversion to 3-methylxanthine, which, before entering the purine catabolism pathway, is further demethylated to xanthine and broken down via the xanthine → uric acid → allantoin → allantoic acid → → CO ₂ + NH ₃ route. It has been shown that when theophylline is radioactively labelled, the label will appear in caffeine and theobromine through the resynthesis of caffeine via the theophylline → 3-methylxanthine → theobromine → caffeine pathway ( Ito et al. 1997). The fact that theophylline was difficult to find in various tests on Mate may be due to the metabolism of theophylline into caffeine and theobromine.

Yerba Mate is often sold in the form of dried ground leaves; however, it has been suggested that the drying process can significantly affect the caffeine concentration as well as the colour and chlorophyll content of the leaves. Schmalko et al. (2001) examined the caffeine, colour and chlorophyll content of Mate leaves after 3 stages of drying. The first stage was blanching, sapeco, at a temperature of 500 to 550 °C for 2 to 4 minutes; stages 2 and 3 are the drying stages, barbaqua, at a temperature of about 110 °C. These drying stages showed a dramatic decrease in caffeine (30%) and chlorophyll (70% to 80%) concentration and a reduction in the green colour. However, even though the caffeine concentration in the dried product was lower than in fresh leaves, evidence from Bastos et al. (2006ashowed that when the leaves were dried and used to prepare Mate infusions, significantly more caffeine and caffeoylquinic acids were extracted than when using fresh leaves. This increased extraction of compounds is probably caused by cell rupture during the drying process. This can also be explained by the decrease in moisture concentration in the leaves and the increase in soluble solids during drying, leading to more compounds being dissolved in the infusion. Evidence has also been presented that harvest time plays a role in the concentration of methylxanthines found in Mate, ranging from 1 to 10 mg total methylxanthines/g, depending on the harvest time ( Schubert et al. 2006 ).

Caffeine derivatives

Caffeoyl derivatives found in Mate include caffeic acid, chlorogenic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid ( Filip et al. 2000 ). These caffeine derivatives are the main components responsible for the antioxidant capacity of Mate tea. Figure 4 shows the chemical structure of chlorogenic acid, 4,5-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid and 3,4-dicaffeoylquinic acid. They have been analysed mainly by 2 different methods, spectrometrically (330 nm) and by HPLC, and are often correlated with chlorogenic acid as a standard at a concentration of 6.90 ± 0.09 mg chlorogenic acid/g dry leaves ( Filip et al. 2000). This is representative of 0.48 mg chlorogenic acid/ml and about 72 mg in 1 cup (150 ml) of Mate infusion, prepared with 1.5 g per 50 ml of water ( Mazzafera 1997 ). These compounds can also be identified individually by HPLC and in combination with liquid chromatography/mass spectrometry (LC/MS), with absorption at 242, 228 and 330 nm ( Carini et al. 1998 ; Chandra and De Mejia Gonzalez 2004 ). Figure 5 shows a chromatographic profile generated by our group to identify caffeoyl derivatives in Mate ( I. paraguariensis ) ( Heck and Gonzalez de Mejia 2007 )). It is clear that the main components are chlorogenic acid and its derivatives, as well as dicaffeoylquinic acids: 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid; although the specific identity of each dicaffeoylquinic acid peak has not been described ( Carini et al. 1998 ). This profile agrees with the compounds shown in Table 2 in terms of the concentrations of caffeoyl derivatives found in Mate ( I. paraguariensis ) compared with I. dumosa, I. brevicuspis and I. argentina . This table shows that I. paraguariensiscontains the highest concentrations of caffeoyl derivatives, while other species have significantly lower concentrations and vary in their dicaffeoylquinic acid content ( Filip et al. 2001 ). It is thanks to the high concentrations of these compounds that Mate has a very high overall antioxidant capacity ( Filip et al. 2000 ).

Table 2-. Concentration of caffeoyl derivatives in different Ilex species (% dry weight). ^a

Species	Chlorogenic acid	Caffeic acid	3,4-DCQ	3,5-DCQ	4,5-DCQ
I. paraguariensis	2,800 ± 0,300	0,023 ± 0,004	0,855 ± 0,064	3,040 ± 0,180	2,890 ± 0,060
I. brevicuspis	0,915 ± 0,064	0,005 ± 0,001	0,130 ± 0,010	0,360 ± 0,060	0,490 ± 0,040
I. argentina	0,090 ± 0,015	0,003 ± 0,001	0,047 ± 0,010	0,545 ± 0,049	0,043 ± 0,003
I. dumosa	0,042 ± 0,009	0,012 ± 0,008	0,017 ± 0,001	0,147 ± 0,060	0,070 ± 0,014

^a Adapted from Filip et al. (2001) .
3,4-DCQ = 3,4-dicaffeoylquinic acid; 3,5-DCQ = 3,5-dicaffeoylquinic acid; 4,5-DCQ = 4,5-dicaffeoylquinic acid.

Saponins

Saponins are bitter, highly water-soluble compounds found in many types of plants and are believed to be one of the factors determining the distinctive taste of Mate tea. Not only do they play a role in flavour, but they are also credited with anti-inflammatory and hypocholesterolemic properties ( Gnoatto et al. 2005 ). Several of these compounds, namely triterpenoid saponins with ursolic and oleanolic moieties, have been isolated from Mate leaves. The identified primary saponins contained an ursolic acid moiety and were named: Matesaponin 1, 2, 3, 4 and 5 ( Gosmann et al. 1995 ; Kraemer et al. 1996 ). Table 3 presents the main saponins identified in Mate ( I. paraguariensis), as well as for other Ilex species; common R group substitutions are included. Figure 6 shows the structure of the generic saponin aglycone, to which various R groups are attached. The hypocholesterolemic properties can be attributed to Mate saponin’s inhibition of the passive diffusion of cholic acid and the formation of micelles that cannot be absorbed and are therefore excreted ( Ferreira 1997 ). Table 3-. Saponins from the Ilex genus and their structural differences, including R group substitutions.

Ilex Species	Saponin	ugrupowanie	R	R1	R2	R3
paraguariensis ^a	Matesaponin 1	Ursolic acid	glc(1→3)ara	H	glc	H
	Matesaponin 2	Ursolic acid	glc(1→3)rha(1→2)ara	H	glc	H
	Matesaponin 3	Ursolic acid	glc(1→3)ara	H	glc(1→6)glc	H
	Matesaponin 4	Ursolic acid	glc(1→3)rha(1→2)ara	H	glc(1→6)glc	H
	Matesaponin 5	Ursolic acid	glc(1→3)rha(1→2)ara	H	glc(1→4)glc(1→6)glc	H
affinis ^b	Affinoside I	Pomolic acid	glc(1→3)ara	H	glc	H
crenata ^c	Ilexoside II	Pomolic acid	glc(1→3)ara	H	glc	H
integra ^d	Ilexoside XXV	Hydroxyursolic acid	glc	H	glc	CH2OH _{_} _
	Ilexoside XXVI	Hydroxyursolic acid	glc(1→6)glc	H	glc	CH2OH _{_} _
	ilexoside XXVII	Rotundic acid	ara	H	glc	CH2OH _{_} _
buxifolia ^b	buxifolioside I	Dihydroxyursenoic acid	H	H	glc	CH ₃
buxifolia ^b	buxifolioside II	Dihydroxyursenoic acid	OH	H	glc	COOH
dumosa ^e	Chikusetsusaponin Iva	Oleanolic acid	gluA	H	glc	H
	Dumosaponin 5	Oleanolic acid	glc(1→2)gal	OH	glc	H
	Dumosaponin 6	Oleanolic acid	ara(1→2)ara	H	glc	H
	Dumosaponin 7	Oleanolic acid	gal	H	glc	H
broadleaf ^f	latifolioside F	ileksgenina	rha(1→2)glc(1→3)ara	H	rha(1→2)glc	H
	latifolioside G	polmolic acid	rha(1→2)glc(1→3)ara	H	rha(1→2)glc	H
	Latifoliozide H	Sulfuryzolic acid	rha(1→2)glc(1→3)ara	H	rha(1→2)glc	H
Argentina ^G	Not applicable	Rotundic acid	H	H	glc	COOH
rotunda ^h	ilexosides XXXIII	Oxysulfuryzolic acid	GlcA	H	H	CHO
	ilexosides XXXIV	pedunculate	SO ₃ Na	H	glc	H
	ilexosides XXXV	Rotungenic acid	SO ₃ Na	H	glc	CH2OH _{_} _
	ilexosides XXXVI	Rotungenic acid	glc	H	glc	CH2OH _{_} _
	Ilexosides XXXVII	Rotundic acid	glc	H	glc	H
brevicuspis ⁱ	Brevicuspisaponin I	Hydroxyursolic acid	ara	H	H	CH ₃
brevicuspis ⁱ	Brevicuspisaponin II	Hydroxyursolic acid	ara	H	H	CH2OH _{_} _

gluA = glucuronic acid; glu = glucose; gal = galactose; ara = arabinose; rha = rhamnose; _{SO3Na =} sulfate .
Gnoatto et al. ^2005a ; Taketa et al. ^2004b ; Taketa ^2004c ; Yano et al. 1993 ^d ; Pires et al. 1997 ^e ; Ouyang et al. 1998 ^f ; Pires et al. 2002 ^g ; Amimoto et al. 1993 ^h . Taketa et al. 2000 ⁱ .

Gnoatto et al. (2005) recently developed a method using HPLC with ultraviolet (UV) detection to analyze saponins in Mate. Total recovery of matesaponin 1 was 94.5%, and the total saponin concentration in the aqueous extract was 352 μg/ml from 15 g of dried leaves in 100 ml of water. Although the main saponins in Mate arise from ursolic acid aglycones, 2 minor saponins have also been identified that contain oleanolic acid instead of ursolic acid ( Martinet et al. 2001 ). Pavei et al. (2007) also developed and validated an HPLC method to characterize saponins from the fruit of I. paraguariensis Mate.

Many saponins found in Ilex species have been shown to have antiparasitic properties, including matesaponins 1, 3 and 4. Triterpenoids found in Ilex species have also been confirmed to be antitrypanosomal. Ursolic acid and 4,3-O-[α-D-glucopyranosyl-(1-2)-α-D-galactopyranosyl]oleanolic acid had IC50 ₄ µM against Trypanosoma brucei. These findings may lead to the investigation of the use of these compounds for new antitrypanosomal derivatives (Taketa et al. 2004).

Minerals

Mate also contains high concentrations of inorganic compounds. The minerals aluminium, chromium, copper, iron, manganese, nickel, potassium and zinc are of particular interest due to their importance in human metabolism and development. Using capillary ion electrophoresis with indirect UV detection (Carducci et al. 2000) and atomic absorption spectrophotometry (Tenorio Sanz and Torija Isasa 1991; Vera Garcia et al. 1997), these minerals have been identified at various concentrations and may vary depending on soil and seasonal factors. Using particle-induced X-ray emission (PIXE), Giulian et al. (2007) examined Mate tea brands before and after brewing and found a wide range of minerals, some of which depend on the temperature and volume used for the infusion, namely chlorine and potassium. Wrobel et al. (2000) found an aluminium concentration of 369 ± 22 μg/g, and manganese at 2223 ± 110 μg/g; Mate may prove to be a good dietary source of manganese, depending on bioavailability. It should also be noted that an inverse correlation (correlation coefficients >0.82) was found between the amount of these components leached into the Mate infusion and the concentration of tannins; the best leaching was observed at lower tannin concentrations, with the exception of nickel.

In addition to beneficial elements, Mate may also contain toxic contaminants. Marchisio et al. (2005) developed a method for analyzing lead, using ultrasonic nebulization coupled with inductively coupled plasma optical emission spectrometry (USN-ICP-OES) and polyurethane foam. Their method demonstrated a lead detection process that proved fast, accurate and reliable, and enables the measurement of small concentrations of lead. Lead concentrations in Mate infusions ranged from 7.6 to 8.9 μg/L. The average lead concentration in the commercial Mate tea samples analyzed was 8.1 μg/L. The permissible lead limit in drinking water set by the U.S. Environmental Protection Agency (EPA) is 15 μg/L; therefore the levels found in Mate are well below the level of concern (EPA 2003 ).

Mate adulterers

Adulterations from other Ilex species may be included in the final product, either intentionally or unintentionally. Six common Ilex species found as adulterants in Mate tea were tested for theobromine, theophylline and caffeine. The species analyzed were I. dumosa, I. pseudobuxus, I. brevicuspis, I. theezans, I. microdonta and I. argentina; overall results showed that these other species contained little or none of the above-mentioned compounds. Only trace amounts of caffeine were detected in I. theezans, I. dumosa, I. microdonta and I. pseudobuxus. Furthermore, in I. argentina and I. microdonta only trace amounts of theobromine were detected. Theophylline was quantitatively detected only in I. pseudobuxus at 6 ppm ( Filip et al. 1998 ). Using HPLC and NMR to analyze Ilex varieties, caffeine and theobromine were found only in I. paraguariensis compared to other adulterating Ilex species ( Reginatto et al. 1999 ; Choi et al. 2005 ).

These adulterations can be problematic for the quality of Mate teas due to varying saponin concentrations. Mate tea prepared from I. paraguariensis proved to be the least bitter of all extracts made from adulterated species. Thus, it is possible that the addition of adulterating species may have a significant impact on the bitterness of Mate beverages. Adulterating plants not only contain higher concentrations of bitter compounds, but the fruits of the I. paraguariensis plant itself also contain highly bitter saponins. The inclusion of these fruits in Mate products can lead to increased bitterness and a reduction in overall quality ( Taketa 2004 ).

Many of these species have also been analysed for their saponin concentration. The analysis showed that most species, including I. buxifolia , I. crenata , I. affinis, I. rotunda, I. brevicuspis, I. argentina and I. integra all have saponin aglycones that are absent in I. paraguariensis and I. dumosa ; instead of ursolic acid or oleanolic acid aglycones, they contain hydroxyursolic acid or its derivatives. Among the various Ilex species, I. dumosa is the most common adulterant and its saponin structure most closely resembles that of I. paraguariensis. All adulterating species, including I. dumosa contained a wide variety of saponins, none of which were found in I. paraguariensis . Due to the specificity of saponins, it may be possible to identify adulterants in Mate based on saponin concentration, and thanks to new methods for fast and precise identification of adulterants, this could now be a reliable method for quality control of Yerba Mate products ( Pires et al. 1997 ).

Biological activities and health effects

Table 4 shows an incomplete list of compounds that have been identified in Yerba Mate, along with some of the most important reported biological activities. Table 4—. Compounds identified in Yerba Mate leaves and some of their biological activities.

Compound	Biological activities
Caffeine	Anticancer, anti-obesity, antioxidant, antitumour, diuretic, energising 20 to 200 mg, stimulant, topoisomerase-I inhibitor 0.1 M, topoisomerase-II inhibitor 99 mM, vasodilator
Chlorogenic acid	Antioxidant IC ₅₀ = 54.2 μM, analgesic, antiatherogenic, antibacterial, antidiabetic, anticancer, choleretic
Chlorophyll	Antibacterial, anticancer
Choline	Antidiabetic, cholinergic, lipotropic
Nicotinic acid	Choleretic, hypocholesterolemic 1 to 6 g/day
Pantothenic acid	Antiallergic 100 to 500 mg/day, antiarthritic 500 to 2000 mg/day, anti-fatigue
Rutin	Antioxidant IC ₂₈ = 30 ppm IC ₅₀ = 120 μM, anticancer, antitumour promoter, antiulcer, cAMP-phosphodiesterase inhibitor, topoisomerase II inhibitor IC ₅₀ = 1 μg/mL, vasodilator
Tannin	Antioxidant 1/3 quercetin IC ₅₀ = 1.44 μg/mL, anticancer, antitumour promoter, lipoxygenase inhibitor, MAO ^e inhibitor
Theobromine	cAMP inhibitor IC ₅₀ = 0.06 mg/mL, cAMP-phosphodiesterase inhibitor, diuretic 300 to 600 mg/day, stimulant, muscle-relaxant
Theophylline	cAMP inhibitor IC ₅₀ = 0.06 mg/mL, cAMP-phosphodiesterase inhibitor, diuretic, choleretic, stimulant, vasodilator, muscle-relaxant 100 μM
Ursolic acid	Analgesic, antioxidant IC ₅₀ = 10 μM, antioxidant IC ₃₅ = 200 μg/mL, protease inhibitor IC ₈₅ = 18 μg/mL, topoisomerase II inhibitor, antiarrhythmic, anticancer, anti-Alzheimer’s

Based on Duke (1992) .

Antioxidant capacity

It has been found that Mate tea consumption significantly contributes to overall antioxidant intake and provides large amounts of caffeoylquinic acid derivatives, with biological activity potentially beneficial to human health ( Bravo et al. 2007 ). Among all Ilex species, I. paraguariensis shows the highest antioxidant activity and is positively correlated with the concentration of caffeoyl derivatives ( Filip et al. 2000 ; Schinella et al. 2000 ; Bracesco et al. 2003 ; Bixby et al. 2005 ).). The study of Mate’s ability to quench reactive oxygen species (ROS) has been correlated with peroxidase-like activity. This peroxidase-like activity is strongly linked to the concentration of polyphenols in Mate; the higher the polyphenol concentration, the greater the peroxidase-like activity. This means that, from a biological standpoint, polyphenols act similarly to the body’s natural antioxidant enzymes and may prove to be strong supporters of these systems.

The compound that may be primarily responsible for this effect is chlorogenic acid ( Anesini et al. 2006 ).

Mate extract proved to be a very strong inhibitor of oxidative stress caused by ROS, significantly for the liver and heart. The heart is susceptible to oxidative stress during post-ischemic reperfusion, that is, the return of blood flow to an organ and tissue after a heart attack, caused by the generation of ROS. Administration of Mate extract reduced lipid oxidation in the heart by protecting the heart muscle tissue ( Schinella et al. 2005 ).

Recent studies have shown that nitrosative stress, a reaction of peroxides with nitric oxide (NO) forming peroxynitrite (ONOO), causes protein nitration or nitrosylation, lipid peroxidation, DNA damage and cell death. Mate tea was able to prevent 95% of protein nitration in tests on bovine serum albumin; in this regard, Mate outperformed both green tea and red wine. Mate was also tested for peroxynitrite-induced cytotoxicity, associated with stroke and myocardial ischemia, limiting blood flow, and Mate tea showed the greatest inhibition of cytotoxicity compared to green tea and red wine ( Bixby et al. 2005 ). Mate was also able to reduce the hydrolysis of ATP, ADP and AMP (nucleotides), which may help balance the cardiovascular system ( Gorgen et al. 2005).

Hyperglycemia has also been reported to be a cause of diabetic complications due to dicarbonyls involved in the formation of advanced glycation end-product (AGE). Oxidation has been linked to glycation, and Mate extracts show dose-dependent inhibition of dicarbonyl activity ( Gugliucci and Menini 2002 ; Lunceford and Gugliucci 2005 ).

Mate extracts significantly inhibited enzymatic and non-enzymatic lipid peroxidation in rat liver microsomes, and also effectively scavenged peroxides ( Schinella et al. 2000 ). It has been suggested that free radical-induced oxidation of low-density lipoproteins (LDL) plays a role in atherosclerosis. Mate has been shown to inhibit the propagation of LDL oxidation by inhibiting lipid peroxidation, as well as DNA oxidation ( Gugliucci and Stahl 1995 ; Gugliucci 1996 ; Bracesco et al. 2003 ). This mechanism has been shown to be possible in vitro ; however, it is still speculated whether this is possible in vivo. Evidence also indicates that Mate has a significantly greater antioxidant capacity than green tea, 13.1 nmol Trolox equivalent (TEAC)/μg gallic acid equivalent compared to 9.1 nmol TEAC/μg gallic acid equivalent, respectively ( Newell et al. 2007 ).

Weight management and obesity

Obesity is a growing problem in many countries, and current research in many fields is focused on finding ways to curb the epidemic. Mate tea has been shown to have an effect on weight loss and weight management, and current studies have provided some supporting evidence. Obese men and women consuming Mate tea showed a decrease in respiratory quotient (RQ), indicating an increase in fat oxidation ( Martinet et al. 1999 ). A herbal infusion of mate, guarana and damiana showed a drastic slowdown in gastric emptying, as well as a shorter time to feel satiety, thereby increasing the feeling of fullness. This was also followed by a dramatic weight loss after 45 days in overweight patients ( Andersen and Fogh 2001). Mate has been shown to have potential for weight loss and is currently regarded as a dietary supplement. The addition of ingredients such as Mate, guarana and damiana to supplements has proven effective in reducing body weight ( Pittler and Ernst 2004 ). In a randomized, double-blind, placebo-controlled clinical trial, Mate was administered as a supplement that also contained extracts of green tea, asparagus, black tea, guarana and beans. The results of this study showed that individuals taking the supplement had reduced body fat and a change in body composition indicators ( Opala et al. 2006). It has been cited that the effect of mate on weight loss, although not directly known, may result from the caffeine it contains, which contributes to lipolytic activity, or from the concentration of saponins, disrupting cholesterol metabolism and delaying the absorption of dietary fat in the intestines ( Dickel et al. 2007 ). Mate tea may also affect other aspects of lipid metabolism. It has the ability to inhibit atherosclerosis in rabbits fed a high-cholesterol diet and an aqueous extract of Mate tea ( Mosimann et al. 2006 ). Administration of Mate extracts to rats fed a hypercholesterolemic diet resulted in a reduction in serum cholesterol and triglyceride levels ( Paganini Stein et al. 2005). Mate has also been shown to have potential as a digestive aid due to its choleretic effect, increasing the rate of bile flow ( Gorzalczany et al. 2001 ). One study also showed that Mate is able to relax arterial vessels in rats. It is thus suggested that the tea may reduce the risk of heart disease, as red wine is believed to do ( Mccillo Baisch et al. 1998 ).

Genotoxic and mutagenic effects

There is little data on the toxicity of Mate tea, and standard in vitro tests are controversial. In one study, Mate extracts proved genotoxic in bacterial cells by inducing functions regulating responses to DNA damage and disruptions in DNA replication, and mutagenic in Salmonella typhimurium . The Ames test showed mutagenic activity at concentrations of 20 to 50 mg of aqueous extract/plate and genotoxic activity at concentrations of 10 to 20 mg of aqueous extract/plate. However, when the S9 microsomal fraction, catalase, thiourea or dipyridyl were added to the test, the genotoxic effect of Mate was neutralised, suggesting that oxygen-reactive factors are responsible for the genotoxicity ( Leitao and Braga 1994 ;Fonseca et al. 2000 ). The results of these in vitro tests have not been confirmed in animal studies or human studies.

The Link Between Mate and Carcinogenesis

Cancer Prevention In vitro and animal experiments have shown the protective effect of Mate against cancer. Several studies have been conducted on the anticancer properties of Mate tea, and comparisons have been made with other teas, such as green tea, which are believed to have high anticancer potential ( Yamamoto et al. 1997 ). Tests conducted by Ramirez-Mares et al. (2004) on the in vitro chemopreventive effect included cytotoxicity, TPA-induced ornithine decarboxylase (ODC), quinone reductase (QR) activity using HepG2 cells, and topoisomerase inhibition activity using Saccharomyces cereviseae. These tests are particularly important because cytotoxicity is strongly linked to anticancer activity. ODC is a tumour growth promoter, and cancer cells often contain high concentrations of ODC. QR is another screening method for anticancer activity, and topoisomerase is required for mitosis; cancer cells show higher concentrations of topoisomerase II (Topo II) than normal cells due to their high rate of cell division. Mate has been shown to have the highest cytotoxicity against human liver cancer cells compared to green tea, with an IC50 _12.01 g eq. (+) catechin/ml for Mate compared to 72 g eq. (+) catechin/ml for green tea. Table 5 shows the tea concentrations needed for various inhibitory activities on HepG2 cells. Table 5—. Inhibitory effect of Mate, green tea and Ardisia tea on the growth of HepG2 cancer cells. ^a

	μg eq. (+) catechin/ml ± SD
	Mate	Green Tea	Ardisia
IC ₁₀	9,3 ± 0,6	50,7 ± 2,5	4,9 ± 1,4
IC50 _{_}	12,0 ± 0,2	72,0 ± 1,8	46,9 ± 3,3
IC ₉₀	17,6 ± 0,8	113,6 ± 5,5	177,2 ± 33,4

^{a Based on} Ramirez-Mares et al. (2004) .
IC10 , IC50 , IC90 _{= concentration needed to inhibit}_10%,₅₀ % and 90% of cell growth, respectively.
SD = standard deviation.

Human antitopoisomerase II activity was significant, showing 65% inhibition compared to 15% for green tea ( Ramirez-Mares et al. 2004 ). However, the catalytic inhibition of topoisomerase concerned only TopoII, and not topoisomerase I (Topo I). An in vitro study on oral cancer cells showed that concentrations higher than 375 μg solid extract/ml caused complete inhibition of cancer cell growth ( Gonzalez de Mejia et al. 2005 ). Mate has been shown to be a potent TopoII inhibitor, and thus shows significant inhibition of cancer cell growth even at low concentrations.

Proteasome inhibitors are an important aspect of cancer research ( Osanai et al. 2007 ). Epigallocatechin gallate (EGCG), found in green tea, has already been shown to inhibit proteasomes ( Osanai et al. 2007 ). Similarly, compounds have been identified in Mate that show inhibition of proteasomes ( Arbiser et al. 2005). The identified compounds are 3,5-dicaffeoylquinic acid (3,5-DCQ), 5-caffeoylquinic acid (5-CQ) and 3,4-dicaffeoylquinic acid (3,4-DCQ), which act by inhibiting chymotrypsin-like activity of purified 20S proteasome and 26S proteasome in Jurkat T cell extracts (human, peripheral blood, leukaemia). Of all these compounds, 3,5-DCQ showed the greatest inhibitory capacity. It is believed to act similarly to EGCG due to its similar structure ( Arbiser et al. 2005 ).

Other compounds found in Mate have also been studied for their chemopreventive properties. Rutin and quercetin show distinct cytotoxicity towards HepG2 cells ( Alía et al. 2006 ). Although these compounds occur in small concentrations in Mate, they demonstrate the diversity of flavonoids present in Mate that contribute to its anticancer potential.

Epidemiological studies There is growing concern over the fact that there are epidemiological studies suggesting a link between mate consumption and an increased risk of developing certain cancers, namely cancers of the esophagus, oral cavity, lungs, bladder, kidneys, and other head and neck cancers ( Pintos et al. 1994 ; De Stefani et al. 1996, 1998 ; Goldenberg et al. 2003 ; Bates et al. 2007 ). These cases were strongly correlated with regions where high consumption of Mate persists, parts of Brazil and Uruguay. However, it is also recognized that other habitual factors, such as smoking and alcohol consumption, which are strongly associated with the culture of these regions, may play a role.Goldenberg (2002) and Goldenberg et al. (2003, 2004) report epidemiological studies showing an increased incidence of squamous cell carcinoma with increased Mate consumption, even when other confounding factors such as smoking were present. The results of these studies indicate that consuming more than 1 liter of Mate daily can increase the risk of head and neck cancer by 3 to 5 times, as well as a clear association with lung cancer ( Vassallo et al. 1985 ; De Stefani et al. 1996 ; Sewram et al. 2003). It has also been reported that consuming strong and very hot tea may increase the risk of oral cancer. Consumption of other hot beverages, coffee and green tea, also increased this risk by 2 to 4 times. Thus, the measured risk of oral cancer may result from thermal injury ( Rolon et al. 1995 ; Castellsague et al. 2000 ). With regard to bladder cancer, epidemiological studies again conducted by the same leading authors ( De Stefani et al. 1991) conducted in Uruguay showed that a link between mate and bladder cancer was found when associated with smoking, and to some extent also in non-smokers, though less clearly defined. The same study also showed that consumers of black tea and coffee had an increased risk of bladder cancer. An epidemiological study conducted in Argentina found an increased risk of bladder cancer in mate drinkers who also smoked, but not in non-smokers ( Bates et al. 2007 ). It is not clear whether this increased risk of bladder cancer results solely from Mate itself, from smoking alone, from a combination of both, or from an entirely different cause.

It should also be noted that case studies on mate consumption and increased cancer incidence also include people who consume black tobacco and alcohol, namely wine. De Stefani et al. (1988) found a correlation with increased risk of oral cancer in people who consume wine, Mate, and smoke. It was also noted that this increase is greater in people who smoke black tobacco than light tobacco. Again, there is no direct implication that any single factor contributes more to this increase in oral cancer cases. Due to these other confounding factors, Mate may not be a carcinogenic factor in itself, but due to the high temperature during consumption it may actually act as an agent that increases the absorption of carcinogens found in cigarette smoke and other environmental pollutants that are carcinogens or cancer promoters ( Goldenberg et al. 2004 ).

On the other hand, Mate may contain compounds that could contribute to cancer. Fagundes et al. (2006) showed a correlation between the amount of Mate consumed and the amount of polycyclic aromatic hydrocarbons (PAHs) in the body. PAHs, especially benzo[a]pyrene, are known to have carcinogenic properties, and tobacco smoke and grilled meat contain high concentrations of PAHs; at least 15 PAH compounds have been found in Mate varieties. These compounds were isolated and identified using stir bar sorptive extraction (SBSE) and high-performance liquid chromatography with fluorescence detection (HPLC-FLD) ( Zuin et al. 2005). The total PAH content in various samples of Brazilian mate ranged from 600 to 2300 ng/l, with naphthalene, acenaphthene, and phenanthrene showing the highest concentrations. Table 6 shows the PAH compounds identified in Mate and their average concentration in 11 Mate samples. Table 6—. Average concentration of polycyclic aromatic hydrocarbons in Brazilian Mate tea samples. ^a

Compound	ng/L	Compound	ng/L
acenaften	426,3	Benzo(b)fluoranthene	11.4
fenantren	347,5	Chrysene	10,5
Naphthalene	96,5	Benzo(a)anthracene	9.7
Fluoranthene	61,4	Indeno(1,2,3)pyrene	9.5
Pyrene	59.1	Benzo(g,h,i)perylene	7.7
Anthracene	50,9	Dibenz(a,h)anthracene	5.0
Fluorene	29,7	Benzo(k)fluoranthene	3.6
Benzo(a)pyrene	12.2

^a Based on Zuin et al. (2005) .

It is known that exposure to PAHs through tobacco smoke and other sources may increase the risk of squamous cell carcinoma of the esophagus (ESCC). Fagundes et al. (2006)evaluated 200 healthy adult Mate tea consumers, half men, half women, half of whom were smokers and half non-smokers, to determine the concentration of 1-hydroxypyrene glucuronide (1-OHPG), a PAH glucuronide metabolite excreted from detoxification in urine. Its presence is evidence that a person has been exposed to PAHs. 1-OHPG can be measured in urine using immunoaffinity chromatography, synchronous fluorescence spectroscopy, and a urinary cotinine strip test; the tests were carried out by the Natl. Cancer Institute at Johns Hopkins Univ. This study showed that there is a direct correlation between the amount of Mate consumed and the concentration of PAHs in urine, the higher the intake, the higher the concentrations. Table 7shows the increasing concentration of 1-OHPG in urine with increasing Mate consumption. Table 7—. Urinary concentration of 1-hydroxypyrene glucuronide (1-OHPG) in humans. ^a

Mate consumption (ml/day)	1-OHPG (pmol/ml)
<100	1.01
>100	1,97
>500	3.24
>1000	4.06

^{a Based} on Fagundes et al. (2006) .

However, in addition to the increase in Mate consumption itself, higher concentrations of 1-OHPG may also be correlated with the combination of smoking and drinking Mate. When Mate consumption is combined with smoking, 1-OHPG concentrations are significantly higher, but Mate alone produces on average roughly the same concentrations of 1-OHPG as smoking alone ( Fagundes et al. 2006 ). During a study of a population in Campinas, SP, Brazil, and the coffee and Mate they consumed, PAHs were detected in all products and ranged from 10.12 μg/kg for coffee to 0.70 μg/kg for Mate ( Rojo de Camargo et al. 2002). Given the estimated average daily consumption of Mate tea in Brazil at 69.79 g, it can be assumed that Mate tea provides about 0.05 μg of total PAHs to the intake of these contaminants by the study population ( n = 600) ( Rojo de Camargo et al. 2002 ).

Although there is no proven biological correlation between drinking Mate and the development of cancer ( Pereira Jotz et al. 2006 ), PAH contamination provides a plausible explanation for the increased rate of Mate drinking and cancer. It is highly likely that PAHs are obtained during processing, since Mate is commonly dried over a smoking fire. Wood smoke may therefore produce the PAHs found in Mate. There also appears to be a clear lack of new information on this topic. Although many articles have been published on this subject, no new evidence has been presented. This is an area that requires further research.

Technological considerations

Flavor and aroma

Preferences and consumer perception are key attributes of any food product, and the same can be said for Mate tea. Sales performance and brand choice, as well as consumer preferences regarding Mate brands, are largely driven by aroma and flavour properties. Generally, sensory panels perform the analysis of these characteristics; however, this is costly and dependent on the sensitivity of the panelists. Therefore, an automated method for determining aroma is needed. Grigioni et al. (2004) showed that the use of an e-nose can differentiate the aroma characteristics of Mate and correlates with the properties assessed by trained panelists.

It has been shown that there is a direct correlation between consumers’ flavour and aroma preferences and the product’s appearance ( Cruz et al. 2003 ; Schneider et al. 2006 ). When sensory panels are used, key terms need to be generated to define the taste, aroma and appearance of Mate products. Descriptors of these characteristics, which have been shown to differentiate products, are presented in Table 8 ( Santa Cruz 2002 ; Cruz et al. 2003 ). Consumer panelists have also been used to test bitterness ( Calvino et al. 2004 ). Table 8—. Sensory Descriptors of Yerba Mate. ^a

Dry Mate Appearance	Infused Mate Appearance	Taste and Aroma
Stick and leaf size	Sediment	Initial impact
Uniformity of stick and leaf size	Turbidity	Acid
Amount of sticks	Brown colour	Moist
Amount of dust		Smoke
		Paper
		Chemical
		Green
		Roasted
		Aftertaste
		Bitterness

^{a Based} on Cruz et al. (2003) .

Aromatic compounds found in Mate have also been characterised using gas chromatography/mass spectrometry; although not correlated with sensory analysis, it shows the chemical composition of Mate’s volatile components. It has been shown that Mate contains over 250 components, many of which are the same as those in green tea. However, a number of distinct components have been identified, namely 2-butoxyethanol (in high concentrations) and compounds related to 3,3,5-trimethylcyclohexanone. Of the 196 volatile chemical compounds found in Yerba Mate tea, only 144 are found in green tea ( Kawakami and Kobayashi 1991 ).

Yerba mate infusions can be prepared from green mate, dried ground leaves, or roasted green mate, where the dried leaves are further roasted to intensify the flavor. This roasting process has been shown to have a dramatic effect on the taste and aroma of the tea. Numerous studies have been carried out to examine the volatile compounds found in Mate. Roasted Mate showed higher concentrations of furans, pyrazines and pyrroles compared to green Mate, likely due to the Maillard reaction ( Kawakami and Kobayashi 1991 ). Bastos et al. (2006b)examined essential oil extracts from green and roasted mate and found that roasted mate contained significantly fewer compounds responsible for the green-floral aroma, namely limonene, which are characteristic of green mate. They also found an increase in compounds such as methylfurfural and furfural, which may be responsible for the smoky character of roasted Mate. Table 9 shows the volatile compounds found in green and roasted Mate tea compared to black tea, identified through aroma analysis using solvent-assisted flavor evaporation – solvent extraction (SAFE-SE). ( Kawakami and Kobayashi 1991 ). Table 9—. Volatile compounds in green Mate and roasted Mate compared to Camellia sinensis tea (black tea). ^a

Compound	Green Mate	Roasted Mate	Black Tea	Compound	Green Mate	Roasted Mate	Black Tea
(E)-2, (E)-4-heptadienal	•	•	•	dihydroaktynidiolid	•	•	•
(E)-2-decenal	•	•	•	eugenol		•
(E)-2-hexenal	•	•	•	furfural	•	•	•
(E)-2-pentenal	•	•	•	furfuryl alcohol	•	•	•
(E)-2-pentenol	•	•	•	geranium	•	•	•
(E)-2-nonadecenal	•	•	•	geraniol	•	•	•
(E)-3,(Z)-5-octadien-2-one	•	•	•	geranyloceton	•	•	•
(E)-3,(E)-5-octadien-2-one	•	•	•	gwajakol	•	•	•
1,3,5-trimethyl-2-(1,3-butadienyl)benzene	•	•		heptanoic acid	•	•	•
2,10,10-trimethyl-6-methylene-l-		•		heptanol	•	•	•
2,3-dihydro-2-methylbenzofuran	•	•		heksanal	•	•	•
2,6,6-trimethyl-2-hydroxycyclohexanone	•	•	•	hexanoic acid	•	•	•
2,6,6-trimethylcyclohex-2-ene-1,4-dione	•	•	•	I-penten-3-ol	•	•	•
2-acetylofuran	•	•	•	I-phenylpropanone	•	•	•
2-butoksyetanol	•	•		limonen	•	•	•
2-dekanon	•	•	•	linalol	•	•	•
2-etylofuran	•	•	•	linalool oxide I (cis, furanoid)	•	•	•
2-metylo-2-pentenal	•	•		linalool oxide II (trans, furanoid)	•	•	•
2-methyl-3-buten-2-ol	•	•	•	linalool oxide III (cis, pyranoid)		•	•
2-methylbutanoic acid	•	•	•	linalool oxide IV (trans, pyranoid)	•	•	•
5,6-epoxy-ionone	•	•	•	methyl salicylate	•	•	•
5-metylofurfural	•	•	•	Nerol	•	•	•
6,10,14-trimethylpentadecanone	•	•	•	nonanowy	•	•	•
6-methyl-(E)-3,5-heptadien-2-one	•	•	•	o-krezol	•	•	•
6-methyl-5-hepten-2-one	•	•	•	octanoic acid	•	•	•
acetic acid	•	•	•	oktanol	•	•	•
a-ionon	•	•	•	pentanal	•	•	•
a-terpineol	•	•	•	pentanol	•	•	•
benzaldehyd	•	•	•	fenol	•	•	•
benzyl alcohol	•	•	•	propionic acid	•	•	•
butyric acid	•	•	•	valeric acid	•	•	•
decanoic acid	•	•	•	β-ionone	•	•	•

Kawakami and Kobayashi (1991 ⁾ .
Compounds represent 0.5% or more of the total concentration.

Lozano and others (2007) used 3 different methods to determine the volatile aroma compounds present in Mate. SAFE-SE analysis identified the largest number of compounds, followed by adsorption column extraction with aroma extract dilution analysis (ACE-AEDA) and dynamic headspace dilution analysis (DHDA), which showed a similar number of compounds. However, each method identified compounds that were not identified by the other methods. Therefore, it is recommended to use multiple methods to analyze volatile aroma compounds. Table 10 presents the main aroma compounds and their characteristic scent identified using 3 different methods for 1 Mate tea. Table 10—. Main volatile aroma compounds in Mate found using 3 different analytical methods. ^a

Compound	SAFE	ACE-AEDA	DHDA	Scent
(E)-2-decenal	•		•	Green, sharp
(E)-2-Nonenal	•		•	Hay
(E)-2-octenal	•	•	•	Raw peanut
(E,E)-2,4-hexadienal	•			Fatty, metallic
(E,Z)-2,6-nonadienal	•	•	•	Cucumber
(Z)-1,5-octadien-3-one			•	Metallic
(Z)-2-Nonenal			•	Melon, hay
(Z)-3-Hexenal	•			Green, cut leaf
(Z)-4-heptenal	•		•	Rancid
1,8-Cineole	•	•		Minty, eucalyptus
1-Hexen-3-one	•		•	Plastic
1-Octen-3-ol	•	•	•	Mushroom
1-penten-3-jeden	•	•	•	Plastic, rancid
2,3-butanedione	•		•	Buttery, creamy
2,3-methylbutanal	•			Chocolate
2,3-pentanedione	•			Buttery, creamy
2-acetylo-1-pirolina	•	•	•	Roasted, popcorn
2-acetylo-2-tiazolina		•		Roasted, popcorn
2-acetylotiazol	•	•		Roasted, popcorn
Butanoic acid	•	•	•	Sweaty, cheesy
Citronellol	•		•	Fruity
eugenol	•	•	•	Cloves, spicy
furaneol	•			Burnt sugar
Geranial	•	•	•	Fruity, floral
Geraniol	•	•	•	Floral
Guaiacol	•	•	•	Smoky, medicinal
heksanal			•	Green, cut grass
Hexanoic acid	•	•		Sweaty, body odour
Linalool	•	•	•	Floral
Maltol		•		Burnt sugar
metionalny	•	•	•	Boiled potato
β-Damascenone	•			Cooked apple
nonalakton	•	•	•	Coconut, sweet
o-krezol		•		Phenol, medicinal
oktalakton	•			Fruity, floral
Octanal			•	Orange oil
p-krezol	•	•		Phenolic, animal, manure
Pentanoic acid	•			Sweaty, cheesy
p-vinyl guaiacol	•	•		Cloves, spicy
Skatole	•	•		Urine, mothballs
Wine lactone	•			Plastic
β-Damascenone		•	•	Cooked apple
β-ionone	•	•	•	Floral

^{a Based} on Lozano et al. (2007) .

One of the characteristic features of Mate teas is the perception of bitterness. This trait can be attributed to caffeine ( Ley et al. 2006 ; Keast and Roper 2007 ), as well as tannins ( Drinkine et al. 2007 ) and saponins ( Ma et al. 1989 ). It should be noted that the presence of stems, often found in most varieties, can significantly reduce the concentration of bitterness compared to varieties without stems ( Calvino 2005 ).

Compound extraction

Although mate is consumed mainly as a beverage, made by steeping the plant’s leaves in hot water, its high concentration of beneficial compounds makes it an interesting subject for extracting and purifying these compounds for use in the nutraceutical industry. It has been shown that the use of sonication effectively eliminates high concentrations of Mate’s compounds, namely caffeine and theobromine. However, this method is affected by solvent polarity, as well as extraction time and solvent-to-sample mass ratio ( Jacques et al. 2007 ). The sonication method also requires the use of organic solvents, methanol and hexane, which can be problematic when the extracts are intended for human consumption. _{For this reason, supercritical CO2} extraction appears to be more promising for this extraction purpose. By using supercritical CO ₂ extraction, the concentrations of extracted methylxanthines are significantly higher compared to other extraction methods. The use of supercritical CO ₂ has been studied and found to be an effective method for extracting caffeine, with a yield of 98% of total caffeine. This method has also shown that extracting theobromine is possible. It has also been shown that supercritical CO ₂ has a greater affinity for caffeine than theobromine. When ethanol is also used for extraction, extraction efficiency improves by reducing solvent and energy requirements ( Saldana et al. 1999 ; Saldana et al. 2002 ).

The use of CO ₂ in a supercritical state has now been employed to analyse Mate samples in order to determine quality differences. Mate samples were tested using CO ₂ extraction to examine changes in the concentration of caffeine, theobromine, phytol, vitamin E, squalene and stigmasterol resulting from differences in light exposure, drying method and leaf age ( Esmelindro et al. 2004). The data showed that when the products were protected from light, there was a dramatic increase in the concentration of caffeine, theobromine, phytol, and to a lesser extent stigmasterol, with caffeine and theobromine in particular being around 3 times higher. Light exposure does not appear to affect the concentration of vitamin E. Leaf age had an effect on the amount of all compounds; younger leaves showed the highest concentrations of all compounds. When alternative methods to air drying were used, microwave drying allowed for the greatest retention of compounds compared to vacuum drying. These findings are significant because they show that light conditions during growth, leaf age and drying method may play a role in the composition of Mate, which would be important when selecting products for extraction in order to obtain a high-quality extract (Esmelindro et al. 2004 ).

Closing remarks

When comparing Mate to other teas, such as green and black tea, several differences can be noted. First and foremost is the taste and aroma, the distinctly bitter taste of Mate is often described as an acquired taste. Roasted/smoky aromas are also often a highly desirable feature that sets it apart from other teas. It’s not only external qualities that distinguish it from other teas, but also its varied concentration of biological compounds not easily found in other teas. The best known of these compounds are xanthines, theobromine and theophylline, which are credited with its ability to boost energy levels. The concentration of saponins is also noteworthy, as they are not found in high concentrations in other teas; saponins contribute to the flavour and can also be attributed to the anti-inflammatory and hypocholesterolemic properties characteristic of Mate as a medicinal herb. It should also be mentioned that although Mate is rich in many compounds not found in other teas, it does not contain catechins like green tea, and is not as rich in flavonoids as black tea.

The most notable biological activity of Mate is its high antioxidant capacity, which has been shown to be higher than that of green tea, which is advertised as having a very high antioxidant capacity. This high antioxidant capacity is attributed to, and is directly proportional to, its high concentration of polyphenols, namely caffeoyl derivatives. Due to Mate’s high biological activity and high concentration of known active compounds, it is an ideal material for extracting these compounds for use in other food products and supplements. Several products containing certain Mate derivatives are currently available on the market. Most of these are aimed at weight loss, as Mate has shown a correlation with weight loss and weight management. Future research is likely to reveal more precise mechanisms of Mate’s actions in these areas.

Contrary to reports about the carcinogenic properties of Mate, there are scientifically confirmed reports of anti-cancer effects. Yerba mate has been shown to have high cytotoxicity against cancer cells, even higher than that of green tea. Mate has also been shown to be highly effective in inhibiting topoisomerase II, which is responsible for cell division, thereby inhibiting the proliferation of cancer cells. Oral cancer cells have been shown to be completely inhibited when treated with 375 μg of Mate extract/ml. It should also be noted that although Mate does not contain catechins such as EGCG, it does contain compounds with similar effects, such as 3,5-dicaffeoylquinic acid. This compound has been shown to be a potent proteasome inhibitor, comparable to EGCG, which has known proteasome-inhibiting activity and is being studied for cancer treatment.

Conclusions

Yerba Mate has been consumed for centuries, but it has only been scientifically studied over the past 20 years. Growing interest in Mate worldwide has made research into this herbal tea extremely important, as it has shown remarkable potential not only as a consumer beverage but also in the nutraceutical industry. As for carcinogenicity, the latest information suggests that the link between mate consumption and cancer may not stem from raw mate itself, but from contaminants that may be present in processed mate. The high temperature at which Mate tea is consumed may also play a role. Therefore, post-harvest technologies must be improved — in particular, the drying process must be optimised to completely eliminate contaminants. Additionally, good quality control, including during analytical testing,