Molecular Capture and Conformational Change of Diketopiperazines Containing Proline Residues by Epigallocatechin-3-<i>O</i>-gallate in Water

The addition of an aqueous solution diketopiperazine cyclo(Pro-Xxx) (Xxx: amino acid residue) to (?)-epigallocatechin-3-O-gallate (EGCg) led precipitation the complex EGCg and cyclo(Pro-Xxx). molecular capture abilities using were evaluated by ratio amount included in precipitates with that total used. Stronger hydrophobicity side chain residue a higher ability. Furthermore, ability decreased when had hydrophilic hydroxyl group. When cyclo(Pro-Xxx), excluding cyclo(D-Pro-L-Ala), was taken into hydrophobic space formed three aromatic A, B, B? rings EGCg, complex, their conformation maintained space. Based on nuclear Overhauser effect (NOE) measurement, 3-position methyl group cyclo(D-Pro-L-Ala) D2O axial, whereas cyclo(L-Pro-L-Ala) equatorial. 2 : its changed from axial position equatorial due steric hindrance EGCg.