Procyanidin polymers

The method of Kato and Nakai (27) for determining protein surface hydrophobicity was adapted for evaluating procyanidin binding to BSA and Gl. The procedure is based on the fact that the fluorescence quantum yield of cis-parinaric acid increases 40-fold when cis-parinaric acid enters a hydrophobic environment from a hydrophilic environment. The digestion of BSA by trypsin in the presence of procyanidin dimer, procyanidin trimer and black bean procyanidin polymer was evaluated by discontinuous sodium dodecyl sulfate (SDS) slab gel electrophoresis and a picryl sulfonic acid (TNBS) assay (28). 

Unlike some classes of polyphenols such as flavonols and flavones, flavanols are almost always present in the nonglycosylated form. Removal of glycoside from flavonoids, usually necessary before the transport across the intestinal barrier, is not required in the case of flavanols [Scalbert and Williamson, 2000]. The absorption of procyanidins by the small intestine was investigated by studying 14C-( + )-catechin, dimer, trimer, and procyanidin polymers permeation through Caco-2 cell cultures [Deprez et al., 2001]. There was little difference in permeability between monomer, dimmer, and trimer, based on the measurement of radioactivity present on the basal side of the cultures, whereas the permeability of the polymers was 10 times lower. The authors reported the absence of catechin metabolism but did not determine whether the radioactivity measured on the basal side of the cultures was from the parent dimers to polymers or from their products of degradation or metabolites, which could have resulted from instability of the parent compounds in the culture... 

Procyanidin polymer (flavan-3-ol polymer) Pistacia lentiscus (Anacardiaceae) ACE (at -10 pM) [80]... 

The current study seeks to extend our knowledge of the behavior of procyanidins in two areas important to their industrial utilization 1) the viscosity of procyanidin polymers in aqueous solutions, and 2) the stoichiometry and rate of reaction of procyanidins with formaldehyde. 

Viscosity Measurements. These were carried out on solutions of the procyanidin polymers using a Ferranti-Shirley cone viscometer at 25.0 0.1 °C with a 3.5-cm-radius cone. This viscosity was measured at several rotation rates to check for shear dependence. The results were constant over the ranges used (20 to 500 revolutions per minute, depending on the viscosity), and the resulting viscosity values were averaged to obtain the results in the test. 

These results may be compared with viscosities obtained in a similar way from conifer bark extracts which, while heterogeneous, contain polymeric pro-cyanidins or mixed polymeric procyanidins and prodelphinidins as their predominant components (2). For example, Weissman (25) reported a viscosity of 65 mPa-s for a 30% solution of the water extract from Pinus oocarpa bark, and Dix and Marutsky (26) obtained a value of 31 mPa-s for a similar solution from Picea abies bark. These viscosities are similar to those observed for the 30% procyanidin polymer solutions. They indicate that the viscosities of these bark extract solutions are dominated by the proanthocyanidins and that there is little influence from any accompanying polysaccharides-as already suggested by Weissmann (25)-in contrast to wattle extracts where gums play an important role in determining solution viscosities (7). 

Ayla (27) reported a viscosity of 65 mPa-s for a 40% solution of the bark extract from Pinus brutia. This is very much lower than that obtained for the T. cacao procyanidin polymer, even though Ayla s (27) estimate of 7-8 for the number-average degree of polymerization was apparently higher than the value of 6.1 obtained for the T. cacao polymer. However, it has recently been shown that the P. brutia polymer is actually a procyanidin-O-glucoside (28). When... 

In contrast, Yazaki and Hillis 29) obtained a viscosity of 8,500 mPa-s for a 45% solution of the aqueous extract from Pinus radiata bark. This is almost an order of magnitude higher than that expected on the basis of the procyanidin polymer results. Viscosities of the methanol-soluble portion and the ultrafiltered portions of this extract were 500 and 90 mPa-s, respectively. The former value is about that expected for a proanthocyanidin polymer, but the latter indicates that most of the polymer has been excluded by the filter, and it further implies that molecular sizes of proanthocyanidins based on ultrafiltration measurements are often misleading. 

Figure 3. Representation of the general structure of a procyanidin polymer chain that has undergone alkaline rearrangement. R = H, or a continuation of the same type of structure [after reference (15)] ...

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

Procyanidin monomers through decamers can be separated on normal-phase HPLC according to the degree of polymerization. Procyanidin polymers with DP >10 elute as a single peak after decamers. No other HPLC method is known to achieve similar or better results. Two types of normal-phase columns may be chosen to separate proanthocyanidins. One option is to use unmodified silica as a stationary phase. Good separation of proanthocyanidins was achieved on a 250 x 4.6 mm silica column (Luna, 5 pm particle size, part number 00F-4274-E0,... 

The theoretical yield for a dimer is 50 %, but for procyanidin B2, for example, only 30 % [11,104] or determined by HPLC (high performance liquid chromatography) 13 % [118], respectively, could be obtained. Procyanidins with a higher degree of polymerization produce more anthocyanidin than dimers, because more "upper units" exist which can be converted into carbocations [113]. For a procyanidin polymer with an average degree of polymerization of 9.4 a cyanidin yield of 58 % is reported [113]. 

Procyanidins are water-soluble polyphenols independent of their molecular weight [87]. Naturally occurring procyanidin polymers show highly irregluar structures, with 4—>8 as well as 4—>6 bondings and branch points. Branched, globular rather than linear, thread-like structures therefore predominate [164]. Helical structures have only been reported for homopolymers of (+)-catechin and (-)-epicatechin [165]. In aqueous solutions procyanidins tend to form associates via hydrogen bonds but do... 

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. 

Condensed T. are polymers in which the monomeric unit is a phenolic flavan, usually a flavan-3-ol, and in which the flavan units are link by 4 8 (C-C) bonds. Many higher oligomers and polymers of Proanthocyanidins (see) are therefore condensed vegetable T. An example is the procyanidin polymer from the seed coat of sorghum (Fig.). SynAesis of condensed T by hiomimetic condensation reactions has been reported. The condensation sequence is initiated by flavan-3-oIs acting as nucleophiles, and fla-van-3,4- ols as potential 4-carbenium ions [J.XBetha et al. Phytochemistry 21 (1982) 1289-1294 CL Hartisch H. Kolodziej Phytochemistry 42 (1996) 191—198]. 

Condensed tannin (or procyanidin polymer) from seed coat of sorghum. n=4-5. M, 17(X)-2000... 

Brieskom CH, Betz R (1988) Procyanidin polymers, the crucial ingredients of the almond seed coat. Z Lebensm Unters Forsch 187 347-353... 

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