Procyanidin tetramer

The profile (%) of polyphenolics in tamarind pericarp was dominated by proan-thcyanidins in various forms, such as (+)-catechin, procyanidin B2, (-)-epicatechin (9.4), procyanidin trimer (11.3), procyanidin tetramer (22.2), procyanidin pentamer (11.6) and procyanidin hexamer (12.8), along with taxifolin (7.4), apigenin (2.0), eriodictyol (6.9), luteolin (5.0) and naringenin (1.4) of total phenols, respectively. Tamarind seeds comprised procyanidins only, represented (%) mainly by oligomeric procyanidin tetramer (30.2), procyanidin hexamer (23.8), procyanidin trimer (18.1), procyanidin pen-tamer (17.6), with lower amounts of procyanidin B2 (5.5) and (-)-epicatechin (Sudjaroen et al., 2005). 

Procyanidin tetramer Kandelia candel (Rhizoporaceae) ETC - NADH DH complex... 

Fig. 9D.12 Flow nephelometric analysis of the inhibitory effect of gum arabic on aggregate formation between procyanidins (tetramers-digaUate and pentamers-gaUate, 0.034 g/L) and BSA (0.33 g/L) (adapted from Carvalho et al. 2006a)...

The A-type proanthocyanidins are characterized by a second ether linkage between an A-ring hydroxyl group of the lower unit and C-2 of the upper unit. Since they are less frequently isolated from plants than the B-types, they have been considered unusual structures [18,19]. The first identified A-type proanthocyanidin was procyanidin A2 isolated from the shells of fruit of Aes-culus hippocastanum. Since then, many more A-type proanthocyanidins have been found in plants, including dimers, trimers, tetramers, pentamers and ethers [18,21]. 

The limited numbers of new propelargonidins are listed in Table 11.7. This is in addition to the mixed procyanidin-propelargonidin tetramer, davallin (Table 11.5), " the mixed propelargonidin-procyanidin trimer, epiafzelechin-(4(S 8)-epicatechin-(4(S 8)-catechin (Table 11.5), and the mixed propelargonidin-prodelphinidin-procyanidin pentamer... 

Figure 16.8 Influence of an increasing gradient of gum arabic concentration on the interactions between BSA (5 x 104mM) and a fraction of procyanidins from grape seed (gallate tetramers and pentamers, 0.034gl" ) (in 12% aqueous ethanol, 0.1 M acetate buffer, pH 5.0) [81].

Figure 16.10 Influence of the concentration of procyanidins (gallate tetramers and pentamers) on the aggregation with two salivary proteins (a) a-amylase (0.4pM) and (b) IB8c (0.5p/W) in 12% aqueous ethanol, 3.1 mM acetate buffer, pH 5.0 [104],...

Procyanidin dimer, trimer, tetramer, and pentamers have molecular masses of 578, 866, 1154, and 1442, respectively. They can be easily identified using a mass spectrometer if [M H] m/z 577, 865, 1155, or 1441 are observed. Proanthocyanidins have three fragmentation... 

Figure 2. Relative IC50 values for the antioxidant effect of dimer, tetramer, and hexamer. Antioxidant effect was evaluated in liposomes incubated at 37°C during 60 min in the presence of different oxidant systems 1) AAPH 10 mM II) AMVN 10 mM III) 25 pM ferrous iron/25 pM ascorbate IV) UV irradiation. Black bars are relative values for IC50 calculated considering the concentration of the procyanidins based on moles of monomer equivalent and gray bars for relative IC50 calculated considering the concentration of procyanidins...

The now familiar protocol of Lewis acid-induced coupling of 0-protected C-4 oxygenated catechin and epicatechin electrophiles of type (165) with 0-protected catechin and epicatechin nucleophiles such as (50), was extended to also include the utilization of equimolar amounts of TMSOTf This approach provided access to procyanidins up to the tetramer level. The same authors reported the tris-(pentafluorophenyl)borane-catalyzed self-condensation of the flavan-3,4-diacetate (166), leading to a complex mixture that was shown by MALDITOFMS analysis to contain procyanidins up to the pentadecamer level. 

The known naturally occurring prodelphinidins and their derivatives, notably the 3-0-gallates, have been extensively reviewed. Although they occur in a broad spectrum of plants, their numbers are limited compared to those of the procyanidins. The chemistry of the prodelphinidins closely matches that of the procyanidins (e.g., see Ferreira and Li" ). Notably amongst the prodelphinidins is that they often occur as mixed oligomers esterified at one or more of the C-3 hydroxy groups, for example, the mixed procyanidin-prodelphinidin tetramer (181). ... 

The crucial question for the final chromatographic analysis is, which procyanidins are to be expected in a given matrix. Naturally occurring procyanidins predominantly consist of either (-)-epicatechin or (+)-catechin. In the (-)-epicatechin series procyanidins B2, B5, Cl and an (-)-epicatechin tetramer co-occur (i.e. in Crataegus sp.), while principal components in the (-t-)-catechin series are procyanidins B3, B6, C2 and a (+)-catechin tetramer (i.e. in Salix sp.). Predominance of procyanidins B1 (i.e. in Rubus sp.) or B4 (i.e. in Sorghum sp.) is relatively seldom in the plant kingdom. The main procyanidins are always accompanied by the... 

The B-ring substitution pattern influences the absorbance. Pure prodelphinidin polymers show much lower specific absorption coefficients (El% = 62) than pure procyanidin polymers (E 0/o = 130) [141]. The molar absorption coefficients of dimeric and higher oligomeric procyanidins are similar (see Tab. (8)). The overall UV absorbance of an oligomer approximately amounts to the sum of the absorbances of the monomer units [226,254], However, UV detection of individual procyanidins after chromatographic separation implies that - in this case - molar absorbances depend on structure. In the series (+)-catechin, procyanidin B2, Cl and a tetramer molar absorbances decreased [262], Treutter et al. [154] found lower molar absorbances for dimers with a 2,3-cis stereochemistry (procyanidin B2 and B5) compared to (-)-epicatechin and (+)-catechin which nearly showed identical molar calibration plots. The molar absorbance of the doubly-linked procyanidin A2 was much higher than the ones of the monomers. 

Jacques et al. (176) isolated two trimeric procyanidins that contained both (4yff 8)- and (4)ff- 8 2)ff- 0->7)-interflavanoid bonds, and partially defined their structures. Nonaka et al. (275) have now unequivocally established the locations of interflavanoid bonds in a series of these compounds from Cinnamomum zeylanicum (cinnamon), including a trimer, two tetramers (59), and a pentamer. The cinchonains such as 60 and 61, cinnamate derivatives of procyanidins are among the more unusual structural variations that have been found in the procyanidins (273). These compounds emphasize the high degree of nucleophilicity of the phloroglucinol ring in procyanidins. These no doubt are examples of a vari-... 

The approach we have found to be most useful for the isolation and purification of Type 1 or 2 proanthocyanidin polymers is extraction from plant tissue with acetone-water mixtures (25, 37), separation of the monomers and lower oligomers from the resulting aqueous solution with ethyl acetate, adsorption on Sephadex LH-20 of the aqueous solution diluted with an equal volume of methanol and washing with the same solvent to eliminate impurities. The polymer is then displaced with acetone-water to yield freeze-dried analytically pure material (25). In the case of procyanidins, the ethyl acetate fraction contains monomers (catechin or epicatechin), dimers, trimers, and some tetramers, whereas the LH-20 fractions contain tetramers, on up to genuinely polymeric species. 

The bitter and astringent taste of cider from specific varieties of bitter apples is caused by the presence of oligomeric procyanidins, mainly tetramers and higher oligomers. Procyanidins sometimes cause the bitter taste of grape wines, especially white wines. 

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