Interactions of Gallic Acid with Porcine Hemoglobin: Effect on the Redox State and Structure of Hemoglobin

Abstract

The effect of gallic acid (GA) on the redox state of hemoglobin (Hb) and the structural mechanism upon the Hb− GA interaction were investigated. Results indicated that GA exhibited antioxidant and pro-oxidant effects on Hb, which depended on its concentration and the redox state of Hb. The antioxidant capacity of GA contributed to the inhibition of free iron release from Hb. GA could bind to the central cavity of Hb and interacted with the heme moiety through direct hydrophobic contacts as indicated by docking analysis, but GA did not disrupt the heme structure. Conversely, GA increased the compactness of the Hb molecule and might narrow the crevice around the heme pocket, which contributed to the inhibition of Hb autoxidation and the free iron release. Results provided significant insights into the interaction of GA with redox-active Hb, which is beneficial to the application of GA in relative meat and blood products.

Binding of Quercetin to Hemoglobin Reduced Hemin Release and Lipid Oxidation

“…The preferred binding area of quercetin on Hb was confirmed by the hydrophobic fluorescent probe (ANS) displacement experiment according to a previous method. 3 The degree of the hydrophobic fluorescent probe (ANS) displaced by quercetin was analyzed by the fluorescence quenching of Hb−ANS complexes after the addition of quercetin. The plots of F/F 0 against quercetin concentrations are shown in Figure S1A.…”

“…Additionally, the presence of quercetin significantly decreased the characteristic peak of porphyrin Soret at 405 nm, demonstrating that quercetin would influence the vicinity to the heme moiety but quercetin did not directly destroy the heme moiety. 3 The percentages of deoxy, oxy, and met-Hb were analyzed from the absorption region of 500−650 nm according to a previous method. 39 S3 indicated that deoxy, oxy, and met-Hb were 9.4, 8.2, and 82.4%, respectively, at the native state (0 h).…”

“…Hb dominates the color and is an active pro-oxidant to promote lipid oxidation in blood and meat foods. 3,7,8 As noted earlier, met-Hb stimulates lipid oxidation in muscle foods whereas reduced Hb (such as oxy-Hb) is not reactive toward lipids. Liberation of ferriprotoporphyrin IX (i.e., free hemin) is related to the initiation of lipid oxidation since hemin released from met-Hb has been found to interact with the phospholipid bilayer and stimulates the formation of reactive radicals.…”

“…21 In a previous study, it has been demonstrated that gallic acid could act as a reductant to dose-dependently retard Hb oxidation by reducing met-Hb formation. 3 As one of the most major flavonoids in plants and human diet, quercetin has been found to be an efficient inhibitor of lipid oxidation in vitro and vivo. 16,22 In addition, the protein−polyphenol interaction is a widespread phenomenon and some flavonoids could bind to Hb with high affinity.…”

Insights into interactions between food polyphenols and proteins: An updated overview

“…Meanwhile, the structural characteristics of the phenolic acids, such as type, hydroxylation, methylation, and steric hindrance, affected their binding affinity to the protein . With regard to phenolic acids, similar measurements have been performed including multi-spectral analysis and molecular docking model, resulting in close conclusion with flavones (Dai et al, 2020;Dong et al, 2021). Alternatively, food and plasma proteins existed in half of the researches as the target including but not limited to serum albumin, lactoprotein, glutelin, and soybean protein (Bhattacharya et al, 2014;Xu et al, 2019;Zhang et al, 2014), which revealed a significant similarity with flavonoids.…”