title: The interaction of phenolic acids with Fe(III) in the presence of citrate as studied by isothermal titration calorimetry.
abstract: Under physiological conditions, exogenous chelators such as polyphenols might interact with non-protein bound ferric complexes, such as Fe(III)-citrate. Additionally, Fe(III) and citrate are widely distributed in various fruits and vegetables which are also rich in phenolic acids. In this study, we focus on the interaction between phenolic acids (gallic acid, methyl gallate and protocatechuic acid) and Fe(III) in the presence of excessive citrate by isothermal titration calorimetry (ITC) for thermodynamic studies, and stopped-flow absorption spectrometry for fast kinetic studies. Results reveal that all of these three phenolic acids can bind to the Fe(III) with the same stoichiometry (3:1). Moreover, the binding constants of these three compounds with Fe(III) are greatly dependent on ligand structure, and are much higher than that of Fe(III)-citrate. Based on their stoichiometry and superhigh binding constants, it is most likely that these three phenolic acids can displace the citrate to bind with one iron(III) ion to form a stable octahedral geometric structure, albeit at different rates. These findings shed light on the interaction between phenolic acids and Fe(III) in the presence of citrate under either physiological conditions or in a food system.
authors.affiliation: CAU & ACC Joint-Laboratory of Space Food, College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Functional Food from Plant Resources, China Agricultural University, Beijing 100083, China.
authors.forename: Senpei
authors.initials: S
authors.lastname: Yang
authors.affiliation: CAU & ACC Joint-Laboratory of Space Food, College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Functional Food from Plant Resources, China Agricultural University, Beijing 100083, China.
authors.forename: Guangling
authors.initials: G
authors.lastname: Bai
authors.affiliation: CAU & ACC Joint-Laboratory of Space Food, College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Functional Food from Plant Resources, China Agricultural University, Beijing 100083, China.
authors.forename: Lingli
authors.initials: L
authors.lastname: Chen
authors.affiliation: CAU & ACC Joint-Laboratory of Space Food, College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Functional Food from Plant Resources, China Agricultural University, Beijing 100083, China.
authors.forename: Qun
authors.initials: Q
authors.lastname: Shen
authors.affiliation: The National Key Facility for Crop Gene Resources and Genetic Improvement (NFCRI), Institute of Crop Science, The Chinese Academy of Agricultural Sciences (CAAS), Beijing 100081, China.
authors.forename: Xianmin
authors.initials: X
authors.lastname: Diao
authors.affiliation: CAU & ACC Joint-Laboratory of Space Food, College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Functional Food from Plant Resources, China Agricultural University, Beijing 100083, China. Electronic address: gzhao@cau.edu.cn.
authors.forename: Guanghua
authors.initials: G
authors.lastname: Zhao
mesh_terms: D002151:Calorimetry; D019343:Citric Acid / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D062385:Hydroxybenzoates / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D005290:Ferric Compounds; D062385:Hydroxybenzoates; D019343:Citric Acid; C017616:phenolic acid
keywords: Isothermal titration calorimetry; Phenolic acids; Stoichiometry; Thermodynamics