Polyphenolic tannin

Investigations have focused on the content or polyphenolics. tannins, and related compounds in various foods and the influence on nutrient availability and protein digestibility. It has been established that naturally occurring concentrations ofpolyphcnoloxtda.se and polyphenols in products such as mushrooms can result in reduced iron bioavailability. Likewise, several studies have locused on decreased protein digestibility caused hy the tannins of common beans and rapeseed (canola). 

Hagerman, A.E., Riedl, K.M., Jones, G.A., Sovik, K.N., Ritchard, N T., Hartzfeld, P.W., and Riechel, T.L. 1998. High molecular weight plant polyphenolics (tannins) as biological antioxidants. J. Agric. Food Chem. 46 1887-1892. 

Water Insoluble High polar (Polyphenols, tannins) Butanol/Acetic acid/Water Butanol/EthanolA/Vater Butanol/Ethyl acetate/Water... 

Phytochemical Content high in carotenoids (lycopene, beta-cryptoxan-thin, beta-carotene), polyphenols (tannins, ellagic acid)... 

Essential oils, diterpenoids, polyphenols, tannins and sugars, phenylpropanoids. 

Natural polymers crosslinked by synthetic molecules represent many resins used for industrial applications. These are now being more closely examined by solid-state NMR spectroscopy to try to understand more fully what occurs in these systems and how it is possible to improve them. Of industrial importance are the polyphenolic tannin resins crosslinked by hexamethylenetetramine. These principally contain flavan-3-ols (Fig. 15.2.18) in the tannin [21] and have been examined by CP/MAS solid-state NMR spectroscopy. Hexamethylenetetramine was used in preference to formaldehyde as it has showed a much faster rate of reaction. The intermediates in this reaction are tribenzyl-, dibenzyl-<(>, and monobenzylamines some of which rearrange to give the dihydroxydiphenylmethane crosslinking bridges in the resin. The exact nature of the crosslinking process, however, is still in debate and the study was undertaken to try and clarify the issue. To examine this process fully, a comparison was made between pine tannin (high in flavan-3-ol) (Fig. 15.2.19) pine tannin hardened with paraformaldehyde (Fig. 15.2.20) and pine tannin hardened with hexamethylenetetramine (Fig. 15.2.21). 

Theae folium Tea Camellia sinensis (L,) KUN1"ZB Theaceae MD 2.5%-4d% caffeine 0.02%-0.03% theophylline 0.05% theobromine Polyphenols tannins catechin type (10% 20%), dimeric thcaBavins, oligomeric procyanidins flavonoid glycosides Fig. 29,30... 

Polyphenols Tannin Tannic acid Hanunamelitannin Commercially available mixture of hydrolyzable tannins usually rangmg from tri- to nona-galloyl glucose Commercially available extract of Hammamelis, a plant containing high concentrations of tannins... 

Le Bourvelleca et al. [17] have investigated the sorption of procyanidins, a polyphenol tannin derivative, on native cellulose fibers and other polysaccharide substrates such as modified pectin and xyloglucan and starch. Through this study, they showed a relatively low affinity of the substrate towards the tested chemical which presented a low adsorbed around 4 mg.g. ... 

High Molecular Weight Plant Polyphenols (Tannins) Prospective... 

In recent years the importance of the marked colloidal nature of tannin extract solutions has come to the fore [27,36-45]. It is the presence of both polymeric carbohydrates in the extract as well as of the higher molecular fraction of the polyphenolic tannins which determines the colloidal state of tannin extract solutions in water [26,36]. The realization of the existence of the tannin in this particular state affects many of the reactions that lead to the formation and curing of tannin adhesives, to the point that reactions not thought possible in solution become instead not only possible but the favored ones [26,36], while reactions mooted to be of determinant importance when foimd on models not in the colloidal state have in reality been shown to be inconsequential to tannin adhesives and their tannin applications [43,44]. 

The polyphenolic tannins are of little importance in the lower orders of plants such as fungi, algae, and mosses, and in most of the monocotyledons such as the grasses (McLeod, 1974). Most of the tannins appear to be found in a few families of the dicotyledons such as the Leguminosae (White, 1957). Singleton and Kratzer (1969) also suggest that specific toxic phenols, and phenols with closely related structures, may be confined to certain families and not infrequently to certain genera, certain species, or even to certain varieties at certain times. Tannins are believed to occur in the vacuoles of intact plant cells (Kramer, 1955 Forsyth, 1964). 

Polyphenols tannins [3] CHCls-MeOH-water (7 13 8 v/v/v), CHCh-MeOH-n-ProOH-water (9 12 2 8 v/v/v/v), n-ButOH-n-ProOH-water (4 1 5 v/v/v)... 

Hagerman, A. and Riedl, K. 1998. High molecular weight plant polyphenolics (tannins) as biological antioxidants. Chem., 46(5) 1887-1892... 

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