**2. Food occurrence of ellagitannins**

Ellagitannins (ETs) are with gallotannins part of the hydrolyzable tannins and constitute the largest group among more than 500 hydrolyzable tannins characterized until now [1]. To date, more than 1000 natural ellagitannins have been identified in nature [2] but most of them are not preponderant in foods. The main ETs identified in foods (specially in fruits, nuts, and seeds) are punicalagin, sanguiin H6, lambertianin C, pedunculagin, vescalagin, castalagin, casuarictin and potentillin (seeds) [3].

Examples of concentration and ellagitannins identified in some foods are presented in **Table 1**. The occurrence of ETs in foods is restricted to a few fruits, such as berries of the genus *Rubus* (cloudberry, raspberry, blackberry, blueberry, and cranberry) and the genus *Fragaria* (strawberry), pomegranate, nuts (walnuts and almonds), seeds, and oak-aged wines [1, 6–8]. Recently, other ET food sources of


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**Figure 1.**

ellagitannins [18].

*Food Ellagitannins: Structure, Metabolomic Fate, and Biological Properties*

tors with content from 1 to 330 mg/100 g (fresh weight basis).

hydrolytic susceptibility, and finally biological activity in vivo [7].

**3. Chemical structure of ellagitannins**

lactonization to form ellagic acid [10, 17] (**Figure 1**).

local importance have been identified such as jabuticaba [4], guava, [5] and grumixama cherries [12]. It is interesting to note that according to a Brazilian research team, Jabuticaba berries from a particular variety cultivated in south Brazil have the highest registered ET content in fruits. Berries have almost three times more equivalent EA content than walnuts and pecans and at least 15 times more than other fruits and nuts [6]. In the berries from the genus *Rubus* and genus *Fragaria*, total equ. EA content represents the most important compounds with 50–88% of total phenolic. Also, ET content can be considerably affected by variety, ripeness, fruit parts, geographic origin, climate, season, cultural practices, and mineral nutrition [6]. ET daily intake is generally low and has been estimated around 5 mg/day for Western diets with major contributors being the red berries mainly strawberries, followed by raspberries and blackberries. Given the significant seasonality of the production of these fruits, the exposure to ellagitannins is very uneven during the year. In the Scandinavian countries, where the consumption of berries increases considerably in summer, daily intake can reach up to 12 mg/day [6, 9] with cloudberry, raspberry, rose hip, strawberry, and sea buckthorn being the main contribu-

ETs are esters of hexahydroxydiphenic acid (HHDP) and a polyol, usually glucose or quinic acid [3, 15, 16], that when they are hydrolyzed spontaneously suffer

Chemical structure diversity among ETs is huge and is due to the possible variations in position, frequency, and stereochemistry of the HHDP units, galloylation extent, and/or anomeric stereochemistry of sugar moieties [17]. Thus, due to seemingly endless structural variations among ellagitannin, elucidating their native structure is often a challenge [17]. According to their chemical structure, ETs can readily undergo different chemical reactions such as transformation, isomerization and oligomerization, which finally determine overall physico-chemical properties,

The important structural diversity of ET structure is due to the different possible extent of galloylation and formation of aromatic C-glycosides, the number of intramolecular C-C coupling of galloyl groups and hydrolytic cleavage of galloyl-derived aromatic rings, the level of dehydrogenation, and oligomerization via oxidative C▬O [2, 17]. According to the number of HHDP groups linked to sugar moiety, ETs can be classified into monomeric, oligomeric, and polymeric

*Basic structures of ellagitannins: (A) HHDP acid (R radical); (B) galloyl unit (G radical); (C) ellagic acid.*

*DOI: http://dx.doi.org/10.5772/intechopen.86420*
