title: Influence of the galloyl moiety in tea catechins on binding affinity for human serum albumin.
abstract: The major catechins of green tea extract are (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg). Recent research has indicated that catechins form complexes with human serum albumin (HSA) in blood, and differences in their binding affinity toward HSA are believed to modulate their bioavailability. In this study, we kinetically investigated the interaction between the catechins and HSA immobilized on a quartz-crystal microbalance (QCM). The association constants obtained from the frequency changes of QCM revealed interactions of ECg and EGCg with HSA that are 100 times stronger than those of EC and EGC. Furthermore, comparisons of these catechins by native-gel electrophoresis/blotting with redox-cycling staining revealed that, in a phosphate buffer, ECg and EGCg have a higher binding affinity toward HSA than EC and EGC. These observations indicate that catechins with a galloyl moiety have higher binding affinities toward HSA than catechins lacking a galloyl moiety.
authors.affiliation: Department of Food and Nutritional Sciences, and Global COE Program, University of Shizuoka, Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Minoda
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Katsumata
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Onobori
authors.forename: Taiki
authors.initials: T
authors.lastname: Mori
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Ishii
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D000975:Antioxidants; D002392:Catechin / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*; D013662:Tea / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D012709:Serum Albumin; D013662:Tea; D002392:Catechin; C062669:epicatechin gallate; C045651:epigallocatechin gallate; C057580:gallocatechol