Abstract
The health benefits stemming from green tea are well known, but the exact mechanism of its biological activity is not elucidated. Epicatechin (EC) and epicatechin gallate (ECG) are two dietary catechins ubiquitously present in green tea. Serum albumins functionally carry these catechins through the circulatory system and eliminate reactive oxygen species (ROS) induced injury. In the present study ECG is observed to have higher antioxidant activity; which is attributed to the presence of galloyl moiety. The binding affinity of these catechins to bovine serum albumin (BSA) will govern the efficacy of their biological activity. EC and ECG bind with BSA with binding constants 1.0×106 M−1 and 6.6×107 M−1, respectively. Changes in secondary structure of BSA on interaction with EC and ECG have been identified by circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy. Thermodynamic characterization reveals the binding process to be exothermic, spontaneous and entropy driven. Mixed binding forces (hydrophobic, electrostatic and hydrogen bonding) exist between ECG and BSA. Binding site for EC is primarily site-II in sub-domain IIIA of BSA and for ECG; it is site-I in sub-domain IIA. ECG with its high antioxidant activity accompanied by high affinity for BSA could be a model in drug designing.
Highlights
Diets rich in antioxidants contribute to lower incidence of several major chronic diseases
Higher antioxidant activity combined with higher binding efficacy with bovine serum albumin (BSA) would be effective in efficient transportation and combating reactive oxygen species (ROS) induced stress
Characteristics of the Fluorescence Spectra There are two tryptophans (Trp 134 and Trp 213) in BSA of which Trp 134 is located on the surface and Trp 213 resides in the hydrophobic pocket of the protein molecule [21]
Summary
Diets rich in antioxidants contribute to lower incidence of several major chronic diseases. Epicatechin (EC) and epicatechin gallate (ECG) are ubiquitous antioxidants present in green tea. These catechins have been investigated for various applications stemming from their antioxidant properties, like radioprotective properties [1] and antioxidative effect [2]. These two catechins are considered under the flavan-3-ol group of flavonoids. Other flavonoids present in green tea, are epigallocatechin (EGC) and epigallocatechin gallate (EGCG) [3]. The chemistry of the C-ring as well as the number and distribution of hydroxyl groups and their substitutions determine the antioxidant activity of these flavonoids in general [4,5]
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