59D-28 |
Mechanism of ellagic acid binding with bovine serum albumin: Influence of reaction temperature, salt, detergents, polyphenols, and starch |
J. E. SCHRIMPF and S. K. Sathe. Food and Excercise Sciences, College of Human Sciences, Florida State University, Tallahasee, FL 32303 Ellagic acid (EA), a naturally occurring phytochemical, found mainly in berries and some nuts, has anticarcinogenic and antioxidant properties. Food processing typically renders soluble EA (glycosylated) into the insoluble form (unglycosylated), and it is not known which form is more bioavailable. Polyphenols bind with proteins, which may influence bioavailability of both. Our objective was to determine the mechanism of interaction between EA (unglycosylated) and a model protein, bovine serum albumin (BSA). EA (50 ug/50 ul pyridine) and BSA (1, 3, 5 mg/ mL 0.2 M sodium acetate buffer, pH 4.0) in EA:BSA ratios of 1:20, 1:60, 1:100 (w/w) were separated after complexation by centrifugation (13,600 g, 15 min, 4C) and quantified individually by spectrophotometric methods. Turbidity analysis (pH 4.0 in 0.2 M sodium acetate buffer) was used to determine the effect of temperature, salt, detergents, catechin, and tannin to the EA:BSA complex. EA solubility increased 5-fold as a result of binding with BSA. The amount of BSA bound to 50 μg EA was 190.4 ± 24.5 mg BSA regardless of initial BSA concentration. Salt (0.01, 0.1, 1.0 M NaCl) had no effect on the EA:BSA complexation. Increased temperature (40șC) enhanced complexation by 35%, whereas lowering temperature to 4șC decreased complexation by 78% compared to baseline at 25șC. Sodium dodecylsulfate, Triton X-100, and Tween 80 (0.05 and 0.1%) decreased complexation by 64.5-73.0% compared to baseline. Corn starch, wheat starch, tannin, and catechin increased EA:BSA complexation by 24-36%, 23-39%, 43-53%, and 21%, respectively, compared to baseline. EA:BSA complexation is primarily governed by hydrophobic interactions. Starch, tannin, and catechin enhance EA:BSA complexation. EA solubility and/or complexation with BSA is thus, partly dependent on environmental conditions and additives. These results suggest that EA interaction with proteins can be effectively manipulated which may help control EA bioavailability.
Session 59D, Food Chemistry: Proteins and Physicochemical Properties
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