Interaction of Catechins with Human Erythrocytes

(-)-Epigallocatechin gallate as an inhibitor of hemoglobin-catalyzed lipid oxidation: molecular mechanism of action and nutritional application

Hemoglobin (Hb) is effective inducer for lipid oxidation and protein-polyphenol interaction is a well-known phenomenon. The effects of the interaction of (-)-epigallocatechin gallate (EGCG) with Hb on lipid oxidation were rarely elucidated. The detailed interaction between bovine Hb and EGCG was systematically explored by experimental and theoretical approaches, to illustrate the molecular mechanisms by which EGCG influenced the redox states and stability of Hb. EGCG would bind to the central pocket of protein with one binding site to form Hb-EGCG complex. The binding constant for Hb-EGCG complex was 0.34 × 104 M-1 at 277 K, and thermodynamic parameters (ΔH > 0, ΔS > 0 and ΔG < 0) revealed the participation of hydrophobic forces in the binding process. The binding of EGCG would increase the compactness of protein molecule and diminish the crevice near the heme cavity, which was responsible for the reduction of met-Hb to oxy-Hb and inhibition of hemin release from met-Hb. Moreover, EGCG efficiently suppressed Hb-caused lipid oxidation in liposomes and cod muscles, which was possibly attributed to the reduction to oxy-Hb state and declined hemin dissociation from met-Hb. Altogether, our results provide significant insights into the binding of EGCG to redox-active Hb, which represents a novel mechanism for the anti-oxidant capacity of EGCG in human health and is favorable to the applications of natural EGCG in the good quality of Hb-containing products.

Pentaclethra eetveldeana Leaves from Four Congo-Brazzaville Regions: Antioxidant Capacity, Anti-Inflammatory Activity and Proportional Accumulation of Phytochemicals

Oxidative stress and inflammation play a key role in the occurrence of neurodegenerative diseases. Traditionally, Pentaclethra eetveldeana leaves are used in dementia treatment. Therefore, this study aimed to evaluate the antioxidant and anti-inflammatory activities as well as the phytochemical composition of Pentaclethra eetveldeana leaves from four Congo-Brazzaville regions. The 1.2-diphenyl-1-picrylhydrazyl radical-scavenging, β-carotene bleaching and molybdenum reduction assays were used to assess the antioxidant activity. The protein denaturation and erythrocyte membrane stabilization tests were used to analyze the anti-inflammatory activity. Phytochemical screening, the quantification of polyphenols by spectrophotometry, as well as the determination of extraction yields were carried out. It was found that the extracts reduced molybdenum; furthermore, compared to ascorbic acid, they showed better antiradical activity and inhibited lipid peroxidation. Moreover, globally, the membrane-stabilizing power of the aqueous extracts was superior or comparable to diclofenac, while the same extracts were less effective for the inhibition of denaturation. All of the aqueous extracts contained polyphenols, saponins, alkaloids, anthraquinones, reducing sugar and cardiotonic glycosides. The total polyphenols, tannins and proanthocyanidins are produced proportionally from one region to another. Finally, the leaves from Brazzaville and Boundji contain flavonols, while those from Makoua and Owando contain flavones. Thus, Pentaclethra eetveldeana leaves contribute to traditional dementia treatment through their antioxidant and anti-inflammatory properties.

Capsaicin toxicity to the yeast Saccharomyces cerevisiae is not due to oxidative stress but to disruption of membrane structure

Capsaicin (CAP) is a common food constituent, conferring a pungent taste to red peppers of the genus Capsicum. It has bactericidal and fungicidal activity. The study was aimed to test the hypothesis of whether oxidative stress mediates the toxicity of CAP to the baker's yeast Saccharomyces cerevisiae as a model yeast. CAP showed good antioxidant properties (1.30 and 1.10 mol Trolox equivalents/mol in the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate (ABTS) radical scavenging assay and the Ferric Reducing Antioxidant Power assay, respectively). However, its autoxidation generated hydrogen peroxide. CAP inhibited the growth of S. cerevisiae at concentrations ≥100 μM. Yeast mutants deficient in superoxide dismutase 1 or catalase T were more sensitive to CAP than wild-type yeast. CAP did not augment the ROS level in yeast cells. Standard antioxidants (N-acetylcysteine and ascorbate) did not protect significantly against CAP-induced yeast growth inhibition. Thus, oxidative stress does not mediate the CAP's inhibition of yeast growth. CAP did not decrease mitochondrial membrane potential of the yeast but induced a concentration-dependent decrease in membrane fluidity. These results indicate that the disturbance of membrane properties is the apparent cause of CAP toxicity to the yeast.

Ultrasensitive catechin electrochemical sensor based on uniform ordered mesoporous carbon hollow spheres (MCHSs) advanced carbon-based conductive materials

Fabrication of an electrochemical catechin sensor composed of mesoporous carbon hollow spheres (MCHSs) and its application in actual sample detection. The MCHSs were obtained using a simple one-pot method without a surfactant.

Novel dual-template molecular imprinted electrochemical sensor for simultaneous detection of CA and TPH based on peanut twin-like NiFe2O4/CoFe2O4/NCDs nanospheres: Fabrication, application and DFT theoretical study

Hollow peanut-shaped NiFe₂O₄/CoFe₂O₄ twinned nano-spherical shell composite materials have interconnected electron channels and excellent electrochemical performance, which prompted the use of this unique spatial structure to fabricate efficient electrochemical sensors. In this work, N-doped carbon dots (NCDs) incorporated into magnetic NiFe₂O₄/CoFe₂O₄ nanoparticle shell (NiFe₂O₄/CoFe₂O₄/NCDs) modified glassy carbon electrode (GCE) was applied to construct a dual-template molecularly imprinted polymer (MIP) based electrochemistry sensor (NiFe₂O₄/CoFe₂O₄/NCDs/MIP/GCE) for the simultaneous detection of catechin (CA) and theophylline (TPH). MIP was fabricated by an in-situ electrochemical polymerization strategy based on the theoretical exploration and density functional theory (DFT) computer directional simulation to screen out the optimal functional monomer (L-arginine) and the optimal ratio between the dual template molecules (CA and TPH) and functional monomer. The materials were characterized by SEM, TEM, XRD, XPS, and TGA. Besides, electron binding energy, binding constant, and imprinting factor were investigated. With the optimal conditions, the proposed electrochemical dual detection system showed outstanding analytical performance for the simultaneous sensing of CA and TPH, with an ultralow detection limit (LOD, S/N = 3) of 1.3 nM for CA in 0.01-1 μM (R² = 0.9956) and 1-50 μM (R² = 0.9928), as well as a LOD of 20.0 nM for TPH in the linear range of 0.1-100 μM (R² = 0.9939), respectively. Also, the selectivity and anti-interference performances of the fabricated sensor were performed by differential pulse voltammetry and chronoamperometry, and successfully detected the analyte from tea drinks and human urine samples with the recovery rates ranging from 98.22% to 104.76% and relative standard deviations (RSD) were 1.19%-3.81%, demonstrated the sensor has excellent stability, repeatability, and reproducibility, which paves the way for other platforms to use this nanomaterial for the detection of antioxidant in the filed food safety.

Changes in Human Erythrocyte Membrane Exposed to Aqueous and Ethanolic Extracts from Uncaria tomentosa

Uncaria tomentosa (Willd.) DC is a woody climber species originating from South and Central America that has been used in the therapy of asthma, rheumatism, hypertension, and blood purification. Our previous study showed that U. tomentosa extracts altered human erythrocyte shape, which could be due to incorporation of the compounds contained in extracts into the erythrocyte membrane. The aim of the present study was to determine how the compounds contained in U. tomentosa extracts incorporate into the human erythrocyte membrane. The study has assessed the effect of aqueous and ethanolic extracts from leaves and bark of U. tomentosa on the osmotic resistance of the human erythrocyte, the viscosity of erythrocyte interior, and the fluidity of erythrocyte plasma membrane. Human erythrocytes were incubated with the studied extracts in the concentrations of 100, 250, and 500 µg/mL for 2, 5, and 24 h. All extracts tested caused a decrease in erythrocyte membrane fluidity and increased erythrocyte osmotic sensitivity. The ethanolic extracts from the bark and leaves increased viscosity of the erythrocytes. The largest changes in the studied parameters were observed in the cells incubated with bark ethanolic extract. We consider that the compounds from U. tomentosa extracts mainly build into the outer, hydrophilic monolayer of the erythrocyte membrane, thus protecting the erythrocytes against the adverse effects of oxidative stress.

Role of Haptoglobin as a Marker of Muscular Improvement in Patients with Multiple Sclerosis after Administration of Epigallocatechin Gallate and Increase of Beta-Hydroxybutyrate in the Blood: A Pilot Study

Here, we report on the role of haptoglobin (Hp), whose expression depends on the synthesis of interleukin 6 (IL-6), related to the pathogenesis of multiple sclerosis (MS), as a possible marker of muscle improvement achieved after treatment with the polyphenol epigallocatechin gallate (EGCG) and an increase in the ketone body beta-hydroxybutyrate (BHB) in the blood. After 4 months of intervention with 27 MS patients, we observed that Hp does not significantly increase, alongside a significant decrease in IL-6 and a significant increase in muscle percentage. At the same time, Hp synthesis is considerably and positively correlated with IL-6 both before and after treatment; while this correlation occurs significantly reversed with muscle percentage before treatment, no correlation is evident after the intervention. These results seem to indicate that Hp could be a marker of muscle status and could be a diagnosis tool after therapeutic intervention in MS patients.