Biology Reference
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9.1.1.1 Oak and chestnut C-glycosidic ellagitannins
Vescalagin ( 1 ) and its C-1 epimer castalagin ( 2 ) are the first C -glycosidic
ellagitannins that have been investigated after their isolation thirty years
ago from Castanea (chestnut) and Quercus (oak) woody species of the
Fagaceae family by Mayer and co-workers (Mayer et al. , 1967, 1969,
1971a). Their structures, as well as those of their 2,3-HHBP-bearing
analogues, stachyurin ( 3 ) and casuarinin ( 4 ) (Okuda et al. , 1981, 1982,
1983), were fully determined much later after revision of their respective
configuration at C-1 by the Nishioka's group (Nonaka et al. , 1990). The
combined amount of these two epimers in the heartwood of oak species
such as Quercus petraea and Quercus robur has been evaluated to vary
from ca . 3 to 57 mg/g of dry wood, depending on the species, age and
sampling position in the tree (Mosedale et al. , 2001, Fernández de Simón
et al. , 1999, Vivas et al. , 1996, Masson et al. , 1995, 1996, Viriot et al. ,
1994). The heartwood of chestnut species such as Castanea sativa can
even contain up to 63 mg of vescalagin ( 1 ) and castalagin ( 2 ) per gram of
dry wood, i.e. , more than 6% (!) by weight of dry material (Viriot et al. ,
1994). Six other NHTP-containing C -glycosidic ellagitannins were later
isolated from fagaceous Quercus and Castanea hardwood species, i.e. ,
the dimers roburins A ( 5 ) and D ( 6 ), and the lyxose/xylose-bearing
monomers grandinin ( 7 ) and roburin E ( 8 ) and dimers roburins B ( 9 ) and
C ( 10 ) (Fig. 9.2) (Nonaka et al. , 1989, Hervé du Penhoat et al. , 1991a/b).
Among these eight typical NHTP-containing C -glycosidic ellagitannins,
vescalagin ( 1 ) and castalagin ( 2 ) largely predominate in the fagaceous
woody species containing them, representing for example between 40%
and about 60% by weight of this group of ellagitannins in Quercus
petraea and robur heartwoods (Fernández de Simón et al. , 1999, Masson
et al. , 1994, 1995, 1996).
Many additional C -glycosidic ellagitannins, including monomers,
oligomers and complex tannins ( vide infra ), have been identified over the
years from species belonging to the selection of plant families mentioned
above (for a compendium of identified structures, see Section 1.3.3 in
Chapter 1 and Sections 2.1.4, 2.1.5 and 2.2.4 in Chapter 2, see also
Haslam and Cai, 1994). A large majority of these structurally complex
natural products (including all types of ellagitannins) has been identified
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