Procyanidins analysis

In the following sections the different analytical approaches to procyanidin analysis will be discussed in detail. 

Whether biosynthesis is enzymatically or thermodynamically driven, naturally occurring procyanidins in either case display a multitude of structural diversity of various degrees of polymerization, which is simply beyond the separating capacity of any chromatographic system. Nevertheless, all classical chromatographic procedures have been applied to procyanidin analysis. Some reviews on the chromatography of procyanidins are also available [26,107,221-222],... 

Table 10. Procyanidin Analysis Using Electrochemical Detection...

Thousands of polyphenols from fruits (grapes, apples, etc.), vegetables (horse beans), and teas have been identified, many having good coloring properties, especially anthocyanins and some flavonoids. Well-documented reviews discuss the coloring capacities of some polyphenols including procyanidins. - Detailed presentations of anthocyanin and flavonoid properties and analysis are included in Sections 2.3, 4.3, and 6.3. The soluble proanthocyanidins of the colored horse bean Viciafaba L. seed coats were isolated and separated by solvent partition. 

Thermodynamic analysis of the binding constants of BSA and procyanidin dimer and trimer from the Van t Hoff equation (29) indicates a reaction with a positive entropy change, a positive... 

Trimeric procyanidin binds more tightly to BSA than dimeric procyanidin (Table II). Partition coefficients of dimeric and trimeric catechin between n-octanol and water indicate procyanidin trimer is more hydrophobic than procyanidin dimer. Increased binding constants of trimer relative to dimer agree with reported partition coefficients. Surface hydrophobicity assays with cis-parinaric acid confirm the thermodynamic analysis that binding of procyanidin to BSA is hydrophobic. 

Fig. 2.95. Chromatographic analysis (HPLC/fluorimetry) of procyanidins in white wine. Reprinted with permission from S. Carando et al. [230].

J. Wollgast, L. Pallaroni, M.-E. Agazzi and E. Anklam, Analysis of procyanidins in chocolate by reversed-phase high-performance liquid chromatography with electrospray ionisation mass spectrometric and tandem mass spectrometric detection. J. Chromatogr.A 926 (2001) 211-220. 

Whitacre, E. et al., Predictive analysis of cocoa procyanidins using near-infrared spectroscopy techniques, J. Food Scl, 68, 2618, 2003. 

ESI-MS in the positive ion mode enabled to detect [M + H] ions up to the galloylated pentamer. Analysis of wine proanthocyanidins showed the presence of additional series of species with 16 mass unit differences to signals given by grape seed procyanidins. These were attributed to the presence of (epi)gallocatechin units in mixed procyanidin prodelphinidin... 

Balas, L. and Vercauteren, J., Extensive high-resolution reverse 2D NMR analysis for the structural elucidation of procyanidin oligomers. Magn. Reson. Chem. 32, 386, 1994. 

X-ray and CD analysis. The structure of procyanidin B-1 was unequivocally confirmed by x-ray analysis of its deca-(9-acetyl derivative by Weinges, one of the pioneers in the field of proanthocyanidin chemistry. One of the most powerful methods to establish the absolute configuration at C-4 of the T-unit in dimeric A- and B-type proanthocyanidins remains the chiroptical method via application of the aromatic quadrant rule. This has been repeatedly demonstrated by the author s own work and several other contributions listed in Refs. 7-12. 

This step is optional, depending on how critical it is to separate anthocyanins from other polyphenolics in subsequent analysis. The ethyl acetate fraction is enriched in polypheno-lics such as flavonols, procyanidins, and cinnamates. If analysis of this fraction is desired, a cleaner isolate will be obtained if residual water is removed by passing a nitrogen gas stream through the cartridge for 2 to 3 min before applying ethyl acetate. 

Reversed-phase HPLC is used for the analysis of the different groups of phenols, phenolic acids, hydroxycinnamic acids, flavonoids, and procyanidins in grapes and wines (22,46,47,77-80). However, due to the presence of a large quantities of various compounds, wine analysis is difficult. Thus, different sample preparation procedures, including fractionation and extraction, are often applied when various groups of phenolic compounds are studied together. 

Table 4 Gradient HPLC Analysis for Phenolic Acids, frans/cis-Hydroxy cinnamic Acids, Flavan-3-Ols, Flavonols, and Procyanidins...

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