Abstract
Catechins, biologically active polyphenols in green tea, exhibit various biological activities, such as anticancer and antiviral activities, arising from interactions with functional proteins. However, the molecular details of these interactions remain unclear. In this study, we investigated the interactions between human serum albumin (HSA) and various catechins, including some with a galloyl group, by means of isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), and docking simulations. Our results indicate that the galloyl group was important for recognition by HSA and was responsible for enthalpic gains derived from a larger buried surface area and more van der Waals contacts. Thus, our thermodynamic and computational analyses suggest that the galloyl group plays important functional roles in the specific binding of catechins to proteins, implying that the biological activities of these compounds may be due in part to the physicochemical characteristics of the galloyl group.
Highlights
Catechins are the major functional components of green tea (Camellia sinensis), and some of these polyphenolic compounds show biological activities, including anticancer and antiviral activities [1, 2], resulting from their interactions with proteins [3,4,5,6,7,8,9]
To focus on the roles of the galloyl group, we analyzed the interaction between human serum albumin (HSA) and Ethyl gallate (EtGa), which was a derivative of the galloyl group (Fig 1C)
Our isothermal titration calorimetry (ITC) results showed that the catechins having the galloyl group (EGCg, epicatechin gallate (ECg), gallocatechin gallate (GCg), and catechin gallate (Cg)) had higher binding affinities than the catechins without a galloyl group (EGC, EC, GC, and C) (S1A Fig, Table 1)
Summary
Catechins are the major functional components of green tea (Camellia sinensis), and some of these polyphenolic compounds show biological activities, including anticancer and antiviral activities [1, 2], resulting from their interactions with proteins [3,4,5,6,7,8,9]. There have been many experimental studies focusing on catechins [5, 8,9,10], the molecular details of the interactions between tea catechins and the proteins involved in their biological activities have not been fully investigated. The main catechins isolated as natural products include (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECg), and (−)-epigallocatechin gallate (EGCg); in addition, various non-natural catechins have been synthesized, including (+)-catechin (C), (−)-gallocatechin (GC), (−)-catechin gallate (Cg), and (−)-gallocatechin gallate (GCg) (Fig 1B) Both the natural and the non-natural catechins have hydroxyl groups (two or three) at the 30-, 40-, and/or 50- positions of the B ring and a hydroxyl group at the 3-position
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