Biology Reference
In-Depth Information
bioavailability and metabolism of ETs and point out various unresolved
issues within this process in humans that still need further research.
7.2 How Relevant Are ETs in the Diet?
ETs are present in significant amounts in many berries (see also Chapter
8), including strawberries, red and black raspberries (Zafrilla
et al.
,
2001), blackberries, and nuts including walnuts (Fukuda
et al.
, 2003),
pistachio, cashew nut, chestnuts, oak acorns (Cantos
et al.
, 2003) and
pecans (Villarreal-Lozoya
et al.
, 2007). They are also abundant in
pomegranates (Gil
et al.
, 2000), and muscadine grapes (Lee and Talcot,
2002), and are important constituents of wood, particularly oak wood
(Glabasnia and Hofmann, 2006). ETs can be incorporated into several
food products such as wines and whiskey, through migration from wood
to the food matrix during different ageing processes. Ellagic acid (EA), a
structural unit of ETs, has also been found in several types of honey and
this phytochemical has been proposed as a honey floral marker for
heather honey (Ferreres
et al.
, 1996). Free EA and different glycosidic
derivatives are also present in these food products, including glucosides,
rhamnosides, arabinosides and the corresponding acetyl esters (Zafrilla
et al.
, 2001).
In a previous review, it was documented that there was no available
reliable figure on the ETs dietary burden, but that it would probably not
exceed 5 mg day
-1
(Clifford and Scalbert, 2000). Since then a number of
studies have shown that the ETs content of several food products can be
quite high (Table 7.1). A glass of pomegranate juice can provide as much
as 300 mg of ETs, a raspberry serving (
ca
. 100 g of raspberries) around
300 mg, a strawberry serving 70 mg, and four walnuts, about 400 mg of
ETs. As a result, the intake of
dietary
ETs can be much higher than
previously estimated (Clifford and Scalbert, 2000), especially if some of
these ETs-rich foods are regularly consumed in the diet.
Representative dietary ellagitannins are shown in Fig. 7.1.
Punicalagin is typical of pomegranate, vescalagin of oak-aged wines and
spirits, sanguiin H-6 of strawberry and raspberry, sanguiin H-5 of
muscadine grapes and pedunculagin of walnuts. All of them release
