Interactions between globular proteins and procyanidins of different degrees of polymerization

Abstract

Interactions of proteins with phenolic compounds occur in food products containing vegetable sources, such as cocoa, cereals, or yogurts containing fruit. Such interactions can modify protein digestion and protein industrial properties. Noncovalent interactions between globular proteins (proteins important in industry) and procyanidins (phenolic compounds present in large quantity in fruits) were studied. The affinity constants between procyanidins of various average degrees of polymerization (DP) and lysozyme or alpha-lactalbumin were measured by isothermal titration calorimetry. The effects of these interactions on protein solubility and foam properties were examined using alpha-lactalbumin and BSA. Weak interactions were found with epicatechin and procyanidin dimers. Procyanidins of n = 5.5 and n = 7.4 showed medium (1.5 x 10(5) M(-1)) and high (8.69 x 10(9) M(-1)) affinities, respectively, for alpha-lactalbumin at pH 5.5, with n the average number of subunits per oligomer. A positive cooperativity of binding at low procyanidin:protein molar ratios was observed. The affinities of alpha-lactalbumin and lysozyme for procyanidins increased when the pH was close to the isoelectric pH. Solubility of lysozyme was strongly decreased by procyanidins of n = 5.5, whereas alpha-lactalbumin and BSA were less affected. Protein solubility in the presence of procyanidins was not affected by increased ionic strength but increased slightly with temperature. Procyanidins of n = 5.5 and n = 7.4 stabilized the average bubble diameter of foam formed with alpha-lactalbumin but had no effect on foam made from BSA. These results indicate that procyanidins of medium can lead to an undesirable decrease of protein solubility, but may play a positive role in foam stability.

Interactions between Pectic Compounds and Procyanidins are Influenced by Methylation Degree and Chain Length

“…39 A previous study on globular protein−procyanidins interactions showed that the higher the degree of polymerization, the higher the affinity constant. 8 Poncet-Legrand et al 40 showed that low polymerized procyanidins are more susceptible to selfassociation than higher polymerized procyanidins and this self-association tendency could limit the association with other compounds such as pectins. Frazier et al 16 showed that grape seed proanthocyanidins in the presence of BSA revealed very weak interactions and suggested that a lack of flexibility in the proanthocyanidins may have contributed to their low affinity.…”

Green tea catechins of food supplements facilitate pepsin digestion of major food allergens, but hampers their digestion if oxidized by phenol oxidase

“…Phenolics such as caffeic, chlorogenic and ferulic acids bind to globular proteins (Li et al, 2010) and readily form insoluble complexes with major peanut allergens, especially Ara h 1 and Ara h 2, and such complexation reduces immunoglobulin E binding (Chung & Champagne, 2009). A recent study provided data on increasing binding affinities of oligomerized polyphenols to globular proteins with increasing degree of polymerization (Prigent et al, 2009). Similarly, a positive correlation was found between the degree of polyphenol oligomerization and inhibition of elastase (Bras et al, 2010) due to an increased number of protein interacting groups.…”

Interaction of phenolic compounds with bovine serum albumin (BSA) and α-amylase and their relationship to astringency perception

“…Tannins were shown to reduce saliva-lubricating ability, both by increasing friction and by reducing its viscosity (Prigent et al, 2009;Prinz & Lucas, 2000). Some authors have shown that the interaction between tannin and salivary proteins is indeed involved in the mechanism of astringency (Horne, Hayes, & Lawless, 2002;Kallithraka, Bakker, & Clifford, 1998).…”