title: Crystallographic evidence for β-cyclodextrin inclusion complexation facilitating the improvement of antioxidant activity of tea (+)-catechin and (-)-epicatechin.
abstract: Single-crystal X-ray analysis to 0.6Å resolution using synchrotron radiation of the inclusion complexes of β-cyclodextrin (β-CD) with (+)-catechin (CA) and (-)-epicatechin (EC) has been carried out to gain atomistic insight into how the inclusion complexation helps to improve tea catechin antioxidant activity. The β-CD-CA complex crystallizes in the monoclinic P21 space group, whereas the β-CD-EC complex crystallizes in both the monoclinic P21 and triclinic P1 space groups. In comparing the inclusion structures, the β-CD-EC dimeric structure having higher numbers of OH⋯O hydrogen bonds combined with π⋯π interactions is associated with its greater interaction energy, as derived from DFT/B3LYP single-point energy calculations. Detailed structural analysis of the CA, EC conformation and inclusion geometry reveals that the interplay of the intermolecular OH⋯O hydrogen bond stabilized catechol moiety and the protection of OH groups in the β-CD cavity plays a key role in the improvement of antioxidant capacity upon inclusion complexation.
authors.affiliation: Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand. Electronic address: athammar@chula.ac.th.
authors.forename: Thammarat
authors.initials: T
authors.lastname: Aree
authors.affiliation: Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Rangsit University, Pathum Thani 12000, Thailand.
authors.forename: Suchada
authors.initials: S
authors.lastname: Jongrungruangchok
mesh_terms: D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology*; D002236:Carbohydrate Conformation; D002392:Catechin / Q000737:chemistry; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D013329:Structure-Activity Relationship; D013662:Tea / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D013662:Tea; D047392:beta-Cyclodextrins; D002392:Catechin; C031215:betadex
keywords: (+)-Catechin; (+)-Catechin (PubChem CID: 107957); (−)-Epicatechin; (−)-Epicatechin (PubChem CID: 72276); Antioxidant activity; DPPH (PubChem CID: 2735032); Ethanol (PubChem CID: 702); Inclusion complex; X-ray analysis; β-Cyclodextrin; β-Cyclodextrin (PubChem CID: 444041)