Re-visiting the Antioxidant Activity of Se- and Te- Carbohydrates: A Theoretical Study

Insights into the Interaction between Polyphenols and β-Lactoglobulin through Molecular Docking, MD Simulation, and QM/MM Approaches

In this work, we have explored the interaction of three different polyphenols with the food protein β-lactoglobulin. Antioxidant activities of polyphenols are influenced by complexation with the protein. However, studies have shown that polyphenols after complexation with the protein can be more beneficial due to enhanced antioxidant activities. We have carried out molecular docking, molecular dynamics (MD) simulation, and quantum mechanics/molecular mechanics (QM/MM) studies on the three different protein-polyphenol complexes. We have found from molecular docking studies that apigenin binds in the internal cavity, luteolin binds at the mouth of the cavity, and eriodictyol binds outside the cavity of the protein. Docking studies have also provided binding free energy and inhibition constant values that showed that eriodictyol and apigenin exhibit better binding interactions with the protein than luteolin. For eriodictyol and luteolin, van der Waals, hydrophobic, and hydrogen bonding interactions are the main interacting forces, whereas for apigenin, hydrophobic and van der Waals interactions play major roles. We have calculated the root mean square deviation (RMSD), root mean square fluctuations (RMSF), solvent-accessible surface area (SASA), interaction energies, and hydrogen bonds of the protein-polyphenol complexes. Results show that the protein-eriodictyol complex is more stable than the other complexes. We have performed ONIOM calculations to study the antioxidant properties of the polyphenols. We have found that apigenin and luteolin act as better antioxidants than eriodictyol does on complexation with the protein, which is consistent with the results obtained from MD simulations.

Organoselenium-chitosan derivative: Synthesis via "click" reaction, characterization and antioxidant activity

The derivatization of chitosan (CS) is widely exploited to endow this polysaccharide with enhanced physicochemical and biological properties. Beyond the synthetic route, the nature of the compounds used to functionalize the CS-derivatives exerts a pivotal role in their final properties. Making use of a simple "click" reaction, we synthesized for the first time an organoselenium-CS derivative through a 1,2,3-triazole formation. The product (CS-TSe) was characterized in detail by FTIR, NMR (¹H, ¹³C, and ⁷⁷Se) and UV-Vis techniques, and SEM microscopy. The antioxidant activity of CS-TSe was examined by ABTS⁺ and DPPH (free radical-scavenging) assays. Experimentally, it was demonstrated that CS-TSe has superior antioxidant activity compared with raw CS and "free" organoselenium compound, suggesting a benign and synergistic effect due to the derivatization. In short, the antioxidant property of CS-TSe combined with the other attractive properties of CS and selenium could be useful in the formulation of advanced materials for biomedical and packaging applications.

An Overview of Structural Aspects and Health Beneficial Effects of Antioxidant Oligosaccharides

BACKGROUND

Non-digestible oligosaccharides are versatile sources of chemical diversity, well known for their prebiotic actions, found naturally in plants or produced by chemical or enzymatic synthesis or by hydrolysis of polysaccharides. Compared to polyphenols or even polysaccharides, the antioxidant potential of oligosaccharides is still unexplored. The aim of the present work was to provide an up-to-date, broad and critical contribution on the topic of antioxidant oligosaccharides.

METHODS

The search was performed by crossing the words oligosaccharides and antioxidant. Whenever possible, attempts at establishing correlations between chemical structure and antioxidant activity were undertaken.

RESULTS

The most representative in vitro and in vivo studies were compiled in two tables. Chitooligosaccharides and xylooligosaccharides and their derivatives were the most studied up to now. The antioxidant activities of oligosaccharides depend on the degree of polymerization and the method used for depolymerization. Other factors influencing the antioxidant strength are solubility, monosaccharide composition, the type of glycosidic linkages of the side chains, molecular weight, reducing sugar content, the presence of phenolic groups such as ferulic acid, and the presence of uronic acid, among others. Modification of the antioxidant capacity of oligosaccharides has been achieved by adding diverse organic groups to their structures, thus increasing also the spectrum of potentially useful molecules.

CONCLUSION

A great amount of high-quality evidence has been accumulating during the last decade in support of a meaningful antioxidant activity of oligosaccharides and derivatives. Ingestion of antioxidant oligosaccharides can be visualized as beneficial to human and animal health.