INTERACTION BETWEEN MILK PROTEINS AND SOME OF PHENOLIC COMPOUNDS

Abstract

Interaction between milk proteins (casein and/or whey protein isolate) and some of standards phenolic compounds (Rosmarinic acid, Chlorogenic acid, Quercetin, Vanillin, Gallic acid, Caffeic acid and Catechin), were determined using Sephadex G-25 column chromatography. Fractions corresponding to protein, protein-phenolic complexes and fractions corresponding to the free phenolics were collected, and their phenolic content was determined by Folin–Ciocalteu reagent. The strongest milk protein-binding affinity was noticed with caffiec acid, whereas chlorogenic acid and vanillin were less interacts with milk proteins. Interaction in the wide range of pH was determined by precipitating potential assay. The optimum pH for the highest interaction was at 3 for rosmarinic acid, quercetin, gallic acid, caffeic acid and catechin, while it was at 5 for chlorogenic acid and vanillin and the lowest interaction for all phenolic compounds was at pH 7. The interaction between tannin fractions isolated from walnuts (Juglans regia), green tea and lentil (lens culinaris L.) and acid casein was determined using fluorescence quenching method and tannic acid standard. The interaction between casein and tannic acid had the most extensive fluorescence quenching and followed by walnut > green tea > lentil for plant tannins. Interaction in wide range of pH was determined by precipitating potential assay. The optimum pH for the highest interaction between casein and tannins was at pH 5, while it was at pH 6 for interaction between WPI and tannins Interaction between tannin fractions from plant source and milk protein fractions [β-casein, κ-casein, β-lactoglobulin (β-Lg) and α-lactoalbumin (α-La)] were determined by high-performance liquid chromatography (HPLC) method with a photo-diode array UV detector. This procedure allows knowing which fraction of milk proteins has the highest ability to interact with tannins. It was found that the highest interaction between tannic acid and β-casein, κ-casein, β-Lg and α-La rather than other tannins. Tannins (green tea) were more interacted with β-casein, κ-casein and α-La than tannins (walnut), where the last was more interacted with β-Lg than tannins (green tea). Phenolic compounds act as anticancer and anti-proliferative but after interaction with milk proteins they form complexes which become less effective rather than these compounds alone. Investigation has been conducted to delineate the action of some phenolic compounds of natural origin and complexes formed from interactions between phenolic compounds and milk proteins on three human tumors cell lines: Breast (MCF7), Liver (HePG2) and colon (HCT116), these interactions were studied by Fourier Transform Infrared Spectroscopy (FTIR) to know which groups do this complex.