title: Polyphenol-Aluminum Complex Formation: Implications for Aluminum Tolerance in Plants.
abstract: Natural polyphenols may play an important role in aluminum detoxification in some plants. We examined the interaction between Al(3+) and the purified high molecular weight polyphenols pentagalloyl glucose (940 Da) and oenothein B (1568 Da), and the related compound methyl gallate (184 Da) at pH 4 and 6. We used spectrophotometric titration and chemometric modeling to determine stability constants and stoichiometries for the aluminum-phenol (AlL) complexes. The structures and spectral features of aluminum-methyl gallate complexes were evaluated with quantum chemical calculations. The high molecular weight polyphenols formed Al3L2 complexes with conditional stability constants (β) ∼ 1 × 10(23) at pH 6 and AlL complexes with β ∼ 1 × 10(5) at pH 4. Methyl gallate formed AlL complexes with β = 1 × 10(6) at pH 6 but did not complex aluminum at pH 4. At intermediate metal-to-polyphenol ratios, high molecular weight polyphenols formed insoluble Al complexes but methyl gallate complexes were soluble. The high molecular weight polyphenols have high affinities and solubility features that are favorable for a role in aluminum detoxification in the environment.
authors.affiliation: Institute of Chemical Industry of Forest Products, Chinese Academy of Forestry , Nanjing 210042, China.
authors.forename: Liangliang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States.
authors.forename: Ruiqiang
authors.initials: R
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States.
authors.forename: Benjamin W
authors.initials: BW
authors.lastname: Gung
authors.affiliation: Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States.
authors.forename: Steven
authors.initials: S
authors.lastname: Tindall
authors.affiliation: National Soil Erosion Research Laboratory, USDA-ARS , West Lafayette, Indiana 47907, United States.
authors.forename: Javier M
authors.initials: JM
authors.lastname: Gonzalez
authors.affiliation: Northern Great Plains Research Laboratory, USDA-ARS , Mandan, North Dakota 58554, United States.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Halvorson
authors.affiliation: Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States.
authors.forename: Ann E
authors.initials: AE
authors.lastname: Hagerman
mesh_terms: D000535:Aluminum / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D005052:Eucalyptus / Q000378:metabolism; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D047348:Hydrolyzable Tannins / Q000737:chemistry; D008970:Molecular Weight; D009942:Organometallic Compounds / Q000737:chemistry*; D010944:Plants / Q000378:metabolism*; D059808:Polyphenols / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D031804:Rumex / Q000378:metabolism; D012995:Solubility
chemical_list: D047348:Hydrolyzable Tannins; D009942:Organometallic Compounds; D059808:Polyphenols; C080077:oenothein B; C435084:pentagalloylglucose; C052082:methyl gallate; D005707:Gallic Acid; D000535:Aluminum
keywords: Gaussian; aluminum detoxification; methyl gallate; oenothein B; pentagalloyl glucose; polyphenols