Diastereomeric difference of inclusion modes between (-)-epicatechin gallate, (-)-epigallocatechin gallate and (+)-gallocatechin gallate, with beta-cyclodextrin in aqueous solvent.
Inclusion complexes of (-)-epicatechin gallate (ECg) as well as (+)-gallocatechin gallate (GCg) and beta-cyclodextrin (beta-CD) in an aqueous solution were investigated using several NMR techniques and a computational method. ECg and EGCg formed a 1:1 complex with beta-CD, in which the A ring and a portion of the C ring were included from the wide secondary hydroxyl group side of the beta-CD cavity, and the B and B' rings were left outside the cavity. GCg formed a 1:2 complex with beta-CD, in which the A and B rings of GCg were included by two molecules of beta-CD. The difference between the two modes of inclusion of the 1:1 complex of ECg, EGCg.beta-CD and the 1:2 complex of GCg.beta-CD might have resulted from the size of the space between the B and B' rings in aqueous solution. As a result of nuclear Overhauser effect (NOE) experiments, GCg was considered to have a large enough space between the B and B' rings to include the B ring in the beta-CD cavity; on the other hand, ECg and EGCg have no such large space.
Ishizu
Takashi
T
Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Sanzo Gakuen-cho 1, Fukuyama, Hiroshima 729-0292, Japan.
Kajitani
Shinya
S
Tsutsumi
Hiroyuki
H
Yamamoto
Hideji
H
Harano
Kazunobu
K
D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry*
D012997:Solvents; D014867:Water; C417940:gallocatechin gallate; D002392:Catechin; C062669:epicatechin gallate; C045651:epigallocatechin gallate