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Insights into antiamyloidogenic properties of the green tea extract (-)-epigallocatechin-3-gallate toward metal-associated amyloid-β species.

Proceedings of the National Academy of Sciences of the United States of America (2013-02-22)
Suk-Joon Hyung, Alaina S DeToma, Jeffrey R Brender, Sanghyun Lee, Subramanian Vivekanandan, Akiko Kochi, Jung-Suk Choi, Ayyalusamy Ramamoorthy, Brandon T Ruotolo, Mi Hee Lim
ABSTRACT

Despite the significance of Alzheimer's disease, the link between metal-associated amyloid-β (metal-Aβ) and disease etiology remains unclear. To elucidate this relationship, chemical tools capable of specifically targeting and modulating metal-Aβ species are necessary, along with a fundamental understanding of their mechanism at the molecular level. Herein, we investigated and compared the interactions and reactivities of the green tea extract, (-)-epigallocatechin-3-gallate [(2R,3R)-5,7-dihydroxy-2-(3,4,5-trihydroxyphenyl)-3,4-dihydro-2H-1-benzopyran-3-yl 3,4,5-trihydroxybenzoate; EGCG], with metal [Cu(II) and Zn(II)]-Aβ and metal-free Aβ species. We found that EGCG interacted with metal-Aβ species and formed small, unstructured Aβ aggregates more noticeably than in metal-free conditions in vitro. In addition, upon incubation with EGCG, the toxicity presented by metal-free Aβ and metal-Aβ was mitigated in living cells. To understand this reactivity at the molecular level, structural insights were obtained by ion mobility-mass spectrometry (IM-MS), 2D NMR spectroscopy, and computational methods. These studies indicated that (i) EGCG was bound to Aβ monomers and dimers, generating more compact peptide conformations than those from EGCG-untreated Aβ species; and (ii) ternary EGCG-metal-Aβ complexes were produced. Thus, we demonstrate the distinct antiamyloidogenic reactivity of EGCG toward metal-Aβ species with a structure-based mechanism.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
(−)-Epigallocatechin gallate, ≥95%
Sigma-Aldrich
(−)-Epigallocatechin gallate, ≥80% (HPLC), from green tea
Supelco
(−)-Epigallocatechin gallate, analytical standard
Epigallocatechin gallate, primary reference standard