title: Enhancement of antioxidant activity of green tea epicatechins in β-cyclodextrin cavity: Single-crystal X-ray analysis, DFT calculation and DPPH assay.
abstract: Green tea catechins are potent antioxidant for prevention of various free radical-related diseases. Their antioxidant properties can be improved by encapsulation in cyclodextrins (CDs). Four inclusion complexes of β-CD with (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG) have been investigated using single-crystal X-ray diffraction analysis combined with full geometry optimization by DFT/B3LYP calculation and the DPPH assay, aiming to deepen the understanding on their structure-antioxidant activity relationship. Scrutinizing the inclusion structures and conformational changes of the four encapsulated epicatechins reveals the common host-guest stabilization scheme and the epicatechin conformational flexibility facilitating the enhancement of activity. Thermodynamic stability order derived from DFT calculation in vacuum fairly agrees with the order of improved antioxidant capacity deduced from the DPPH assay, β-CD-EGCG>β-CD-ECG>β-CD-EGC≈β-CD-EC.
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; D001713:Biphenyl Compounds / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry* / Q000494:pharmacology*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D010851:Picrates / Q000737:chemistry*; D011789:Quantum Theory; D013329:Structure-Activity Relationship; D013662:Tea / Q000737:chemistry*; D013816:Thermodynamics; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D002396:Catechols; D010851:Picrates; D013662:Tea; D047392:beta-Cyclodextrins; C004931:1,1-diphenyl-2-picrylhydrazyl; C031215:betadex; C034221:catechol
keywords: (–)-Epicatechin (PubChem CID: 72276); (–)-Epicatechin gallate (PubChem CID: 107905); (–)-Epigallocatechin (PubChem CID: 72277); (–)-Epigallocatechin gallate; (–)-Epigallocatechin gallate (PubChem CID: 65064); Antioxidant activity; DFT calculation; DPPH (PubChem CID: 2735032); DPPH assay; Ethanol (PubChem CID: 702); X-ray analysis; β-Cyclodextrin (PubChem CID: 444041); β-cyclodextrin