Polyphenols estimation

It is estimated that the mean total intake of polyphenols in the Spanish diet ranges from 2,590 to 3,016 mg/person/day including polyphenols soluble in aqueous-organic solvents, plus insoluble condensed and hydrolyzable tannins. Fruits and vegetables provide a daily intake of 700-1,000 mg of polyphenols/person/diet a major fraction of this (600 mg/person/day) is associated with DF (Saura-Calixto and others 2007). 

Scalbert A (1992) Quantitative methods for the estimation of tannins in plant tissues. In Hemingway RW, Laks PE (eds) Plant polyphenols synthesis, properties, significance, vol 59. Plenum Press, New York, NY, pp 259-280... 

One current estimate of NP diversity totals ryo.ooo different structures, yet this huge chemical diversity is generated from only a few biochemical pathways that branch from the metabolism shared by most organisms. About 60% of the known NP diversity comes from one ancient pathway (the isoprenoids or terpenoids), another 30% comes from some other ancient pathways related to each other (the polyphenols, phenylpropanoids or polyketides) and less than 10% of NPs (alkaloids) comes from a more diverse family of pathways. There seems to be a rough correlation between the number of species possessing one pathway and the total diversity of NPs made by that route. Consequently, the minor groups of NPs that comprise less than 1% of the total NP diversity (e.g., the glucosinolates) tend to be restricted to a small number of species. 

TABLE 6.2 Total polyphenol and tannin estimated in finger millet. (ND, not detectable)... 

Another important field of application concerns food and beverages, especially wine, juices, and tea (A2, A11, A17, B4, K12, V7, Yl). The antioxidant components of food include vitamin E (a-tocopherol), vitamin A (retinoids), vitamin C (ascorbic acid), and also fi-carotene (provitamin A), other carotenoids (of which more than 600 compounds have been identified), flavonoids, simple phenols, and glucobrasicins (H3). Unfortunately, the TAC value of a food is not informative on the bioavailability of its antioxidants. It has been estimated that polyphenols are normally present in blood plasma at concentrations of 0.2-2 //M (PI). However, it has been demonstrated that feeding rats a quercetin-augmented diet can increase their plasma levels of quercetin and its metabolites up to 10-100 //M (M27), and transient increases in the concentration of plant-derived phenolic compounds can take place after ingestion of food and beverages, which may affect blood plasma TAC (see later). 

Another group of compounds which may nutritionally modify TAC of blood plasma is polyphenols. The possible contribution of polyphenolic components of food and beverages to the TAC of body fluids is a subject of controversy. It has been estimated that polyphenols are present in blood plasma at concentrations of 0.2-2 /xM (PI). However, feeding rats a quercetin-augmented diet can increase the plasma levels of quercetin and its metabolites up to 10-100 /xM (M27). 

Ragan, M.A. and Jensen, A., Quantitative studies on brown algal phenols. I. Estimation of absolute polyphenol content of Ascophyllum nodosum (L.) Le Jol. and Fucus vesiculosus (L.), J. Exp. Mar. Biol. Ecol., 30, 209, 1977. 

Bourzeix, M., Heredia, N., Estrella, M. I., Puech, J. L., Fartsov, K. (1980). Estimation quantitative de la matiere colorante rouge des mouts concentres et des vins. Bull. Liaison-Groupe Polyphenols, 9, 131-142. 

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. 

The effect of olive oil polyphenols on LDL oxidation was estimated in various models of chemically and cell-mediated oxidation and evaluating... 

The complexity of polyphenolic composition of plant materials is such that complete identification has not been accomplished for many fruits. Often, compounds are partially characterized with respect to their compound class. Standards are often not available, but estimates of quantities can be made on the basis of reference compounds from the same class. Total polyphenolic levels can be obtained by summing the individual compounds within a class and then summing the different classes. 

In conclusion, the deconvolution procedure seems to be a suitable method for the rapid and simple estimation of global phenolic compound concentration. Commercial built-in spectrophotometer software such as UVPro from Secomam or any multicomponent procedure can be used for this purpose. In this last case, samples have to be filtered in order to avoid interference due to the high TSS level in UV spectrophotometry measurement. Nevertheless, this method must be extended to other phenolic families such as aminophenols or polyphenols. 

---