title: Evaluation of non-covalent interactions between serum albumin and green tea catechins by affinity capillary electrophoresis.
abstract: The natural antioxidant-associated biological responses appear contradictory since biologically active dosages registered in vitro experiments are considerably higher if compared to concentrations found in vivo. The recent research indicates that natural antioxidants, including the major catechins of green tea epicatechin (EC), epigallocatechin (EGC), epicatechingallate (ECG) and epigallocatechingallate (EGCG) form non-covalent complexes with albumin, a crucial aspect that may modulate their plasma concentration, tissue delivery and biological activity. Affinity capillary electrophoresis (ACE) was used to characterize the binding of the four catechins to human serum albumin (HSA) and bovine serum albumin (BSA) at near-physiological conditions: 10 mmol/L phosphate buffer, HEPES 50 mmol/L (pH 7.5), temperature 37°C. The studied flavonoids displayed affinities toward the albumin with binding constants in the range 10(3)-10(5)M(-1), with a greater affinity of catechins toward HSA than BSA (between 3 and 3.5 fold higher). We also confirmed that catechins having a galloyl moiety (ECG and EGCG) have a higher binding affinity toward albumin than the catechins lacking the galloyl moiety (EC and EGC), and that for both albumins the order of affinity is EC<EGC<ECG<EGCG. We believe that our work can provide useful information for better understanding the intercurrent relationships between cathechins bioavailability and their elicited biological effects.
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy. Electronic address: azinellu@uniss.it.
authors.forename: Angelo
authors.initials: A
authors.lastname: Zinellu
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Sotgia
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy.
authors.forename: Bastianina
authors.initials: B
authors.lastname: Scanu
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Pisanu
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Giordo
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Cossu
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Posadino
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy.
authors.forename: Ciriaco
authors.initials: C
authors.lastname: Carru
authors.affiliation: Department of Biomedical Sciences - University of Sassari, Sassari, Italy. Electronic address: gpintus@uniss.it.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Pintus
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000032:analysis* / Q000737:chemistry; D002392:Catechin / Q000032:analysis* / Q000737:chemistry; D002417:Cattle; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D012709:Serum Albumin / Q000032:analysis* / Q000737:chemistry; D013662:Tea / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D012709:Serum Albumin; D013662:Tea; D002392:Catechin
keywords: Affinity capillary electrophoresis; Albumin; Binding constant; Green tea, Catechins