Total proanthocyanidins

The data on hazelnut proanthocyanidins are limited. Recently, Gu et al. [49] found that some tree nuts are good sources of proanthocyanidins with contents ranging from 0.05 in chesmut to 500.7 mg/100 g in hazelnut (Table 13.4). The order of total proanthocyanidin concentration content in tree nuts was as follows hazelnut > pecan > pistachio > almond > walnut > cashew > chestnut. No proanthocyanidins have been detected in Brazil nut, macadamia, and pine nut [49]. Among the proanthocyanidins, polymers are most abundant in hazelnut and some other tree nuts such as ahnond, pecan, and pistachio. Average intake of proanthocyanidins is estimated at 58mg/100g in the United States [49]. 

Documented effects A dry extract from the aboveground parts, as well as the total proanthocyanidins have antihypoxic, antioxidant, angioprotective, and hypocholesterimic abilities (Aizikov et al. 1986). An ethanolic extract of the aboveground plant parts had antiulcerogenic activity in rats (Amani et al. 2006), and a methanolic extract exhibited an antidiarrheal effect (Atta and Mouneir 2004). 

Table 7.2 Concentration of flavan-3-ol monomers, dimers and trimers and total proanthocyanidins in berries ...

The chemical characteristics of the proanthocyanidins were elucidated by total oxidation and partial degradation in the presence of phloroglucinol followed by HPLC analysis. The native extract of proanthocyanidins contained (+) gallocatechin, (-) epigallocatechin, (h-) catechin, and (-) epicatechin units. ... 

Proanthocyanidins (PAs), also known as condensed tannins, are oligomeric and polymeric flavan-3-ols. Procyanidins are the main PAs in foods however, prodelphinidins and propelargonidins have also been identified (Gu and others 2004). The main food sources of total PAs are cinnamon, 8084 mg/100 g FW, and sorghum, 3937 mg/100 g FW. Other important sources of PAs are beans, red wine, nuts, and chocolate, their content ranging between 180 and 300 mg/100 g FW. In fruits, berries and plums are the major sources, with 213.6 and 199.9 mg/100 g FW, respectively. Apples and grapes are intermediate sources of PAs (60 to 90 mg/100 g FW), and the content of PAs in other fruits is less than 40 mg/100 g FW. In the majority of vegetables PAs are not detected, but they can be found in small concentrations in Indian squash (14.8 mg/ 100 g FW) (Gu and others, 2004 US Department of Agriculture, 2004). 

The chemical basis for the observed differences in leaf food quality is unknown. Little differences were found in Folin-Denis total phenolic or proanthocyanidin extinction coefficients of 85% aqueous methanol leaf extracts from the various plant groups throughout the experiment. There were no indications of changes in leaf quality of control willows 60 m distant from willows attacked by fall webworm. 

The extraction of proanthocyanidins is the first step in determining their subunit composition. A number of extraction systems have been investigated in different plant tissues. The most common solvent systems are acetone and methanol with various amounts of water and with or without acid. In general, it has been found that an aqueous acetone system gives the best results in terms of total amount extracted. 

A third method relies on the precipitation of proanthocyanidins with formaldehyde. First, the total phenolic content is measured using the Folin-Ciocalteu reagent as described before. A 0.5 mole equivalent of phloroglucinol (1.3) is added for every gallic acid equivalent in the extract. To 2 mL of this plant extract and phloroglucinol is added 1 mL of a 2 5 HC1 /H20 solution and 1 mL of an aqueous solution of formaldehyde (13 mL of 37% formaldehyde diluted to 100 mL in water). After an overnight incubation at room temperature, the unprecipitated phenols are estimated in the supematent by the Folin-Ciocalteu method. The precipitate contains the proanthocyanidins and the known amount of phloroglucinol, which is always quantitatively precipitated. 

Polymeric fractions were obtained from wines, seed and skin extracts by fractionation on a Toyopearl HW-40 column as described by Souquet et al (4). Two aliquots of the fractions containing polymeric material were t en to dryness under vacuum. The first one was used to determine proanthocyanidin composition by thiolysis followed with HPLC analysis (17). The other one was dissolved in MeOH acidified with 2% HCl and used to estimate the concentration of total polymeric polyphenols and polymeric pigments by measuring the absorbance, respectively at 280 nm and 530 nm. Absorbance data were converted to equivalent epicatechin and equivalent malvidin-3-glucoside, respectively, using the extinction coefficients determined for each compounds under similar conditions. 

Nutrient Content high in protein, prebiotic and insoluble fiber, lignans, antioxidant vitamins A and C, dietary minerals, phytosterols Phytochemical Content high in total carotenoids and polyphenols (anthocyanins, catechins, proanthocyanidins, chlorogenic acid)... 

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