Influence of valoneoyl groups on the interactions between Euphorbia tannins and human serum albumin

Abstract

Tannins belonging to plant polyphenols, are large group of compounds with diverse biological activity. Many of them are being studied as potential natural medicine due to their antioxidant, antiviral, antibacterial or anticancer properties. However, so far little is known about the structural and functional relations in protein-tannin interactions, in particularly the role of valoneoyl groups in tannin structure. In this study we first investigated the mechanisms of interaction 1,2-di-O-galloyl-4,6-valoneoyl-β-D-glucose (Tannin 1), 2-O-galloyl-4,6-valoneoylβ-D-glucose (Tannin 2), 3-O-galloyl-1,2-valoneoyl-β-D-glucose (Tannin 3) isolated from Euphorbia plants with human serum albumin (HSA). To get more detailed information about nature of albumin-tannin interactions besides standard Trp fluorescence quenching analysis we used also transmission electron microscopy (TEM), circular dichroism (CD) and fluorescence labelling (ANS dye) techniques. It was shown that all the tannins strongly interacted with HSA and quenched the tryptophan amino acid (Trp) fluorescence but slightly changed protein secondary structure (circular dichroism CD analysis). TEM demonstrated that all used compounds formed complexes with HSA. Tannin 3 most strongly quenched HSA fluorescence and changed protein dynamic as well as had the highest binding constant (12.4 ± 1.1 × 10 13 M −1 s −1 in comparison with 7.0 ± 0.38 × 10 13 M −1 s −1 for tannin 1 and 8.6 ± 1.1 × 10 13 M −1 s −1 for tannin 2). For tannin 1 that was the largest of the studied compounds was observed the weakest influence on the fluorescence parameters, probably due to the effect of steric hindrance limiting interaction with albumin Trp pocket. On the other hand T1 induced the strongest changed secondary structure of HSA in comparison to another studied tannins. Our results demonstrated that all used tannins interact with albumin by complex formation but in the manner depends on chemical structure and flexibility of studied compounds.

Inhibition of interaction between Staphylococcus aureus α-hemolysin and erythrocytes membrane by hydrolysable tannins: structure-related activity study

“…The smallest antihemolytic effect was exhibited by tannins containing a valoneoyl group (T3, T4) that is a limitation factor of the rotational mobility of the aromatic rings 46 . In addition, these tannins have a carboxyl Figure 7.…”

“…The activity of tannins depends on their structure and is determined not only by molecular mass (MM) and the number of hydroxyl and aromatic rings but also on their location in the molecule, which affects their molecular bulk, flexibility and hydrophobicity, and ultimately their biological effect [42][43][44][45][46] .…”

Effect of sodium sulfite, tartaric acid, tannin, and glucose on rheological properties, release of aroma compounds, and color characteristics of red wine

“…Therefore, acidizing red wine is an important step in red wine making to attain the certain levels of acidity with pleasant taste for wide consumers' acceptability. Further, tannin has been reported to promote the stability of red wine by removing metal ions and lowering the content of aldehydes materials (Picariello et al, 2016) besides its bacteriostatic action (Sekowski et al, 2017). On the other hand, glucose as source of energy or substrate material for yeast used in the required fermentation is mainly resolved into ethyl alcohol and water through glycolysis.…”

Insights into the Binding of Dietary Phenolic Compounds to Human Serum Albumin and Food-Drug Interactions

“…Little is known about the structural and functional relationship between plasma proteins and tannins. Sekowski and coworkers demonstrated that hydrolysable tannins interact very strongly with HSA, with an intensity of the interaction that depends not only on the number of hydroxyl groups, but also on the bulk, flexibility and hydrophobicity of the chemical structure [ 55 , 56 ]. Tannins with higher molecular weight bind with stronger interaction to proteins, but also tannin flexibility has to be considered: the more flexible the structure, the more rotational capacity of the molecule and easier access to protein binding pockets [ 55 ].…”

“…Sekowski and coworkers demonstrated that hydrolysable tannins interact very strongly with HSA, with an intensity of the interaction that depends not only on the number of hydroxyl groups, but also on the bulk, flexibility and hydrophobicity of the chemical structure [ 55 , 56 ]. Tannins with higher molecular weight bind with stronger interaction to proteins, but also tannin flexibility has to be considered: the more flexible the structure, the more rotational capacity of the molecule and easier access to protein binding pockets [ 55 ]. Thus, larger and more flexible molecules are capable of changing the secondary structure of albumin through surface interactions, but the presence of valoneoyl structures limit the capacity of tannins to penetrate the hydrophobic tryptophan pocket [ 55 , 56 ].…”