title: Relationship between the tautomeric structures of curcumin derivatives and their Abeta-binding activities in the context of therapies for Alzheimer's disease.
abstract: Curcumin, which can exist in an equilibrium between keto and enol tautomers, binds to beta-amyloid (Abeta) fibrils/aggregates. The aim of this study was to assess the relationship between the tautomeric structures of curcumin derivatives and their Abeta-binding activities. Curcumin derivatives with keto-enol tautomerism showed high levels of binding to Abeta aggregates but not to Abeta monomers. The binding activity of the keto form analogue of curcumin to Abeta aggregates was found to be much weaker than that of curcumin derivatives with keto-enol tautomerism. The color of a curcumin derivative with keto-enol tautomerism, which was substituted at the C-4 position, changed from yellow to orange within 30 min of being combined with Abeta aggregates in physiological buffer. This resulted from a remarkable increase in the enol form with extended conjugation of double bonds upon binding. These findings suggest that curcumin derivatives exist predominantly in the enol form during binding to Abeta aggregates, and that the enolization of curcumin derivatives is crucial for binding to Abeta aggregates. The keto-enol tautomerism of curcumin derivatives may be a novel target for the design of amyloid-binding agents that can be used both for therapy and for amyloid detection in Alzheimer's disease.
authors.affiliation: Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Japan.
authors.forename: Daijiro
authors.initials: D
authors.lastname: Yanagisawa
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Shirai
authors.forename: Tomone
authors.initials: T
authors.lastname: Amatsubo
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Taguchi
authors.forename: Koichi
authors.initials: K
authors.lastname: Hirao
authors.forename: Makoto
authors.initials: M
authors.lastname: Urushitani
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Morikawa
authors.forename: Toshiro
authors.initials: T
authors.lastname: Inubushi
authors.forename: Masanari
authors.initials: M
authors.lastname: Kato
authors.forename: Fuminori
authors.initials: F
authors.lastname: Kato
authors.forename: Kyuya
authors.initials: K
authors.lastname: Morino
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Kimura
authors.forename: Ichiro
authors.initials: I
authors.lastname: Nakano
authors.forename: Chikako
authors.initials: C
authors.lastname: Yoshida
authors.forename: Takashi
authors.initials: T
authors.lastname: Okada
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Sano
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Wada
authors.forename: Ken-nosuke
authors.initials: KN
authors.lastname: Wada
authors.forename: Akitsugu
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Ikuo
authors.initials: I
authors.lastname: Tooyama
mesh_terms: D000544:Alzheimer Disease / Q000188:drug therapy*; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D003474:Curcumin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D009682:Magnetic Resonance Spectroscopy; D000432:Methanol / Q000737:chemistry; D011485:Protein Binding / Q000187:drug effects; D020836:Protein Structure, Quaternary; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism
chemical_list: D016229:Amyloid beta-Peptides; D012996:Solutions; D003474:Curcumin; D000432:Methanol