Influence of Galloyl Moiety in Interaction of Epicatechin with Bovine Serum Albumin: A Spectroscopic and Thermodynamic Characterization

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.

Salivary α-amylase, serum albumin, and myoglobin protect against DNA-damaging activities of ingested dietary agents in vitro

“…Our study extends prior evidence (Manach et al, 1995; Papadopoulou and Frazier, 2004; Nozaki et al, 2009; Hara et al, 2012; Pal et al, 2012;) that animals have evolved physiological protection against dietary polyphenols and, in particular, PLPs such as EGCG, gallic acid, and pyrogallol. We thus discovered a novel function for saliva in mitigating PLP-induced DNA damage; this is in addition to the known functions of enzymatic activity, moistening, diluting/washing, salivary PRPs binding tannins, and maintenance of tooth integrity through antibacterial activity and specialized interactions with bacterial metabolism in dental plaque (Humphrey and Williamson, 2001).…”

“…Serum albumin and myoglobin also inhibited dietary strand-breaking genotoxic activities. Consistent with a reported interaction between serum albumin and EC (Papadopoulou and Frazier, 2004); Pal et al, 2012, ECG (Pal et al, 2012), and EGCG (Nozaki et al, 2009), albumin might have an important role in providing protection against PLPs to the extent that they enter the blood. Our observations suggest a potential complementary role of dietary myoglobin, from meat consumption by carnivores and omnivores, in limiting DNA damage from dietary PLPs.…”

“…Additionally, tissue proteins, dietary proteins, and albumin in blood might limit DNA damage. Serum albumin, for example, binds quercetin (Manach et al, 1995), EC (Papadopoulou and Frazier, 2004; Pal et al, 2012;), ECG (Pal et al, 2012), and EGCG (Nozaki et al, 2009). …”

Human Serum Albumin Increases the Stability of Green Tea Catechins in Aqueous Physiological Conditions

“…In this context, two major binding regions, namely site-I and site-II, have been reported to be responsible for the ability of HSA to bind aromatic and heterocyclic compounds [ 28 , 29 ]. These domains, which are characterized by the presence of a central cavity formed from six amphiphatic helices, have been recently reported to be the same that are responsible for the binding of HSA with catechins [ 30 ]. It may be possible that by acting through hydrogen bonding and hydrophobic interactions these polyphenolic compounds form reversible non-covalent complexes with HSA.…”

The study on the interaction of Epigallocatechin gallate with bovine serum Albumin

“…For typical hydrophobic interaction, both entropy change (ΔS°) and enthalpy change (ΔH°), are positive, which was different in our results such as ΔS°=14.92 J/mol/K (positive) and ΔH°=-22.67 kJ/mol (negative). The positive entropy observed accounts for hydrophobic interactions and negative enthalpy may play a role in electrostatic interactions, which is also inferred from the decrease in quenching constant with an increase in ionic strength [20]. Docking studies of BSA-EGCG interactions BSA has two Trp residues, for example Trp134 is located on the surface of the molecule, and Trp213 is located within drugbinding site I [21].…”