Inhibition of catalase by tea catechins in free and cellular state: a biophysical approach

Essential Oils of Tunisian Tetraclinis articulata (Vahl) Mast.: Chemical and Biological Insights

Tetraclinis articulata (Vahl) Mast. is native to the Mediterranean area and belongs to Cupressaceae family. The aim of this study were: i) to determine the chemical composition of essential oils (EOs) of T. articulata obtained from its stems, leaves, and cones using GC coupled to GC/MS; II) to evaluate their antioxidant activity using non enzymatic (DPPH, ABTS and FRAP) and enzymatic methods (catalase activity); III) to evaluated their anti-enzymatic activity on enzyme involved in metabolism and Central Nervous System using spectrophotometric assays. α-Pinene, limonene, and bornyl acetate were the main components of the three EOs. Moreover, the EO from cones showed the best antioxidant activity and was also to increase of catalase activity. All EOs were active against α-amylase in similar way; the EO leaves was more active against α-glucosidase and the EO from cones was more active against cholinesterase. The EOs demonstrated significant inhibition of the mature biofilm of Gram-negative and Gram-positive strains. This highlight the potential uses of T. articulata EOs in the fields of health and agriculture.

Experimental and Theoretical Approaches to Monitor the Behavior of Bovine Liver Catalase in Interaction with a Binuclear Bismuth Complex

Here, the antioxidant potency of a binuclear Bi(III) complex {[Bi2(μ-ox)(dipic)2(H2O)2 (taa)2].H2O, where ox2- = oxalato, dipic2- = pyridine 2,6-dicarboxylato, and taa = thiourea} was evaluated using the •DPPH assay. It was demonstrated that the Bi complex exhibited a high ability to inhibit DPPH free radicals. The binding mechanism of the complex with bovine liver catalase (BLC) was also investigated, revealing structural and activity changes in the enzyme in the presence of the complex. The catalase activity in the decomposition of hydrogen peroxide increased in the presence of the Bi complex, reaching 39.8% higher than its initial activity at a concentration of 7.77 × 10-6 M. The complex exhibited a relatively high affinity for BLC, with K b values of 3.98, 0.13, and 0.09 × 105 M-1 at 303, 310, and 317 K, respectively. The mechanisms involved in the interaction were hydrogen bonding and van der Waals interactions, as validated through molecular docking simulations. Synchronous fluorescence showed that tryptophan was more affected by enzyme-complex interactions than tyrosine. In addition, a cell viability test using the MTT method revealed that at its highest concentration, the Bi complex caused a decrease in the number of cells below 50% compared to the control, while cisplatin showed negative effects at all concentrations. These findings suggest that the Bi complex has the potential to be developed as a promising candidate for BLC-related therapeutic target therapy.

Tracking the binding site of anticancer drug fluxoridin with Fe-related proteins to achieve intelligent drug delivery

In cancer cells that need a lot of iron for growth and metastasis, halo-transferrin (TF-containing iron) enters the cell with the help of the transferrin receptor 1 (TFR1) protein. If the anticancer drug can bind to the iron site by interacting with apo-transferrin (iron-free FT), it can enter the cancer cell by the same mechanism. Two iron-related proteins, Bovine liver catalase (BLC) and apo-Transferrin (TF), that are important in cancer patients were selected and their interaction with the anti-cancer drug Floxuridine (FUDR) was investigated. Here, the protective role of FUDR was evaluated by several variables such as drug concentration, interaction time, and temperature-induced degradation of enzyme function. The results showed that the protective effect of the FUDR is greater in high concentrations (in 5 × 10-5 M:1.78 % and 2.59 % after 24 and 48 h). The interaction of the FUDR with both proteins can reduce the intensity of the fluorescence emission by a static mechanism. The binding strength of the FUDR with both proteins was almost similar and with the order of 104 M-1 (Kb = 3.90 ± 0.41 × 104 M-1 for BLC-FUDR and 5.01 ± 0.36 × 104 M-1 for TF-FUDR at 310 K). The thermodynamic calculations (in agreement with the docking results) indicated that FUDR-protein complex formation was exothermic and the main binding forces in the binding process were van der Waals interactions and hydrogen bonds. Both fluorophores tryptophan (Trp) and tyrosine (Tyr) of both proteins had significant roles in fluorescence quenching and the interaction process, the polarity of their microenvironment changed. CD results showed that the secondary structure changes of TF are slightly more than BLC. Molecular docking showed that the binding of the FUDR to TF is very close to the Fe-specific site and is placed in the cavity among the wrapping domain, N-Terminal arm, and β-barrel in BLC.

Hydrophobic quercetin encapsulated hemoglobin nanoparticles: formulation and spectroscopic characterization

Various natural proteins are finding application in drug delivery for their high biodegradability and biocompatibility. Albumins are well explored and now focus is shifting to other proteins like hemoglobin (Hb) with unique structural properties. In the present study Hb is allowed to denature at pH 5.0 and model hydrophobic drug quercetin (Q) is encapsulated via self-assembly and hydrophobic interactions. Fluorimetric titrations record highest binding between Hb and Q at pH 5.0, rendering significant structural changes in Hb as captured in CD spectra. A decrease in fluorescence life time of tryptophan residues from 3.31 ns in Hb to 2.89 ns in presence of Q at pH 5.0; surmises efficient binding of Q at the hydrophobic core housing tryptophan. Peak shifts in Fourier transform infrared spectroscopy spectra of Hb-Q compared to Hb evidence significant interactions between them at pH 5.0. Significant spectral changes in soret band region of Hb on addition of Q at pH 5.0 envisages unfolding of porphyrin ring and binding influence of Q. Efficient formation of Hb-Q nanoparticles (NPs) at pH 5.0 is established by DLS, SEM and TEM.Communicated by Ramaswamy H. Sarma.

Catalases in the pathogenesis of Sporothrix schenckii research

Pathogenic fungal infection success depends on the ability to escape the immune response. Most strategies for fungal infection control are focused on the inhibition of virulence factors and increasing the effectiveness of antifungal drugs. Nevertheless, little attention has been focused on their physiological resistance to the host immune system. Hints may be found in pathogenic fungi that also inhabit the soil. In nature, the saprophyte lifestyle of fungi is also associated with predators that can induce oxidative stress upon cell damage. The natural sources of nutrients for fungi are linked to cellulose degradation, which in turn generates reactive oxygen species (ROS). Overall, the antioxidant arsenal needed to thrive both in free-living and pathogenic lifestyles in fungi is fundamental for success. In this review, we present recent findings regarding catalases and oxidative stress in fungi and how these can be in close relationship with pathogenesis. Additionally, special focus is placed on catalases of Sporothrix schenckii as a pathogenic model with a dual lifestyle. It is assumed that catalase expression is activated upon exposure to H₂O₂, but there are reports where this is not always the case. Additionally, it may be relevant to consider the role of catalases in S. schenckii survival in the saprophytic lifestyle and why their study can assess their involvement in the survival and therefore, in the virulence phenotype of different species of Sporothrix and when each of the three catalases are required. Also, studying antioxidant mechanisms in other isolates of pathogenic and free-living fungi may be linked to the virulence phenotype and be potential therapeutic and diagnostic targets. Thus, the rationale for this review to place focus on fungal catalases and their role in pathogenesis in addition to counteracting the effect of immune system reactive oxygen species. Fungi that thrive in soil and have mammal hosts could shed light on the importance of these enzymes in the two types of lifestyles. We look forward to encouraging more research in a myriad of areas on catalase biology with a focus on basic and applied objectives and placing these enzymes as virulence determinants.

Systems Network Pharmacology-Based Prediction and Analysis of Potential Targets and Pharmacological Mechanism of Actinidia chinensis Planch. Root Extract for Application in Hepatocellular Carcinoma

Purpose

Traditional Chinese medicine (TCM) sometimes plays a crucial role in advanced cancer treatment. Despite the significant therapeutic efficacy in hepatocellular carcinoma (HCC) that Actinidia chinensis Planch root extract (acRoots) has proven, its complex composition and underlying mechanism have not been fully elucidated. Therefore, this study analyzed the multiple chemical compounds in acRoots and their targets via network pharmacology and bioinformatics analysis, with the overarching goal of revealing the potential mechanisms of the anti-HCC effect.

Methods

The main ingredients contained in acRoots were initially screened from the traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP), and the candidate bioactive ingredient targets were identified using DrugBank and the UniProt public databases. Second, the biological processes of the targets of active molecules filtered from the ingredients of acRoots were evaluated using gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Third, weighted gene coexpression network analysis (WGCNA) was performed to identify gene coexpression modules associated with HCC. The hub genes of acRoots in HCC were defined via contrasting the above module eigengenes with candidate target genes of acRoots. Furthermore, the target-pathway network was analyzed to explore the mechanism for anti-HCC effect of hub genes. Kaplan–Meier plotter database analysis was performed to validate the hub genes of acRoots correlation with prognostic values in HCC. In order to verify the results of the network pharmacological analysis, we performed a molecular docking approach on the active ingredients and key targets using the Discovery Studio software. The viability of SMMC-7721 and HL-7702 cells was determined by Cell counting kit-8 (CCK-8) after being treated with different concentrations of (+)-catechin (0, 50, 100, 150, 200, and 250 g/ml) for 24, 48, and 72 hours, respectively. Finally, qRT-PCR and Western blot involving human hepatocarcinoma cells were utilized to verify the impact of (+)-catechin on the hub genes associated with prognosis.

Results

6 out of 26 active ingredients extracted from TCMSP were deemed as the core ingredients of acRoots. 175 bioactive-ingredient targets of acRoots were obtained and a bioactive-ingredient targets network was established correspondingly. The biological processes (BP) of target genes mainly involved processes, such as toxic substance and wounding. The results of KEGG pathways indicated that the target genes were mainly enriched in pathways in cancer, AGE-RAGE signaling pathway in diabetic complications, IL-17 signaling pathway, and other pathways. Also, the two hub genes (i.e., ESR1 and CAT) were closely associated with the prognosis of HCC patients. As a consequence, we predicated a series of signaling pathways, including estrogen signaling pathway and longevity regulation pathway, through which acRoots could facilitate the treatment for HCC. The molecular docking experiment ascertained that ESR1 and CAT had an effective binding force with (+)-catechin, one of the core ingredients of acRoots. Furthermore, (+)-catechin inhibited SMMC-7721 cell growth in a dose-dependent manner and a time-dependent manner. Finally, we suggest that the expression level of ESR1 and CAT is positively related to the (+)-catechin concentrations in in-vitro experiments.

Conclusion

The bioactive ingredients of acRoots, including quercetin, (+)-catechin, beta-sitosterol, and aloe-emodin, have synergistic interactions in reinforcing the anticancer effect in HCC. Evidently, acRoots took effect by regulating multitargets and multipathways through its active ingredients. Further, (+)-catechin, the possible paramount anti-HCC active ingredient in acRoots, helped improve the prognosis of HCC patients by increasing the expression of ESR1 and CAT. Additionally, the findings yielded provide a conceptual guidance for the clinical treatment of HCC and the methods adopted are potentially applicable in the future comprehensive analysis of the underlying mechanisms of TCMs.

Free radical-scavenging composite gelatin methacryloyl hydrogels for cell encapsulation

Gelatin methacryloyl (GelMA) hydrogels have been widely used for cell encapsulation in tissue engineering due to their cell adhesiveness and biocompatibility. However, free radicals generated during gelation decrease the viability of the encapsulated cells by increasing intracellular oxidative stress, so appropriate strategies for scavenging free radicals need to be developed. To meet that need, we developed composite GelMA hydrogels incorporating nanofiber particles (EF) coated with epigallocatechin-gallate (EGCG). The GelMA composite hydrogels were successfully fabricated and had a storage modulus of about 5 kPa, which is similar to that of pristine GelMA hydrogel, and the drastic free radical scavenging activity of EGCG was highly preserved after gelation. In addition, human adipose-derived stem cells encapsulated within our composite hydrogels had better viability (about 1.5 times) and decreased intracellular oxidative stress (about 0.3 times) compared with cells within the pristine GelMA hydrogel. We obtained similar results with human dermal fibroblasts and human umbilical vein endothelial cells, indicating that our composite hydrogels are suitable for various cell types. Furthermore, we found that the ability of the encapsulated cells to spread and migrate increased by 5 times within the composite hydrogels. Collectively, our results demonstrate that incorporating EF into GelMA hydrogels is a promising way to enhance cell viability by reducing free-radical-derived cellular damage when fabricating 3D tissue ex vivo. STATEMENT OF SIGNIFICANCE: Gelatin methacryloyl (GelMA) hydrogels have been widely applied to various tissue engineering applications because of their biocompatibility and cell interactivity. However, free radicals generated during the GelMA hydrogel fabrication decrease the viability of encapsulated cells by elevating intracellular oxidative stress. Here, we demonstrate radical scavenging GelMA hydrogels incorporating epigallocatechin-gallate (EGCG)-coated nanofiber particles (EF). The composite GelMA hydrogels are successfully fabricated, maintaining their mechanical properties, and the viability of encapsulated human adipose-derived stem cells is greatly improved after the gelation, indicating that our composite GelMA hydrogel alleviates damages from free radicals. Collectively, the incorporation of EF within GelMA hydrogels may be a promising way to enhance the viability of encapsulated cells, which could be applied to 3D tissue fabrication.

A combined in vitro-in silico approach for the discovery of novel endogenous enzymatic and ctDNA sequence of bioactive molecules from aerial and root parts of Centaurea sulphurea as antioxidant's agents

The excess free radicals not neutralized by the antioxidant defenses damage the essential macromolecules of our cells, causing abnormalities in the expression of genes and membrane receptors, cell proliferation or death, immune disorders, mutagenesis, deposits of proteins or lipofuschin in tissues. The first objective of this study was to elucidate the composition of the essential oil of the aerial and root part of Centaurea sulphurea during beginning of the vegetative cycle (March), beginning of the flowering stage (April) and full bloom (May/June) using GC/FID and GC/MS. The second aim was to describe the antioxidant activity using three methods (2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), β-carotene bleaching assay) and bioinformatical study of ctDNA sequence and three endogenous enzymes inhibition. The essential oils obtained from the root during the full bloom period consisted mainly of caryophyllene oxide, aplotaxene and (Z)-phytol. While, the aerial parts were dominated by caryophyllene oxide, verridiflorol and humulene epoxide II. The results showed that essential oil presented an excellent antioxidant activity with IC₅₀ values of 2.06 g/L and 1.29 g/L, for aerial and root parts, compared to butylated hydroxyltoluene (BHT) and Ethylenediaminetetraacetic acid (EDTA) controls and the nicotinamide adenine dinucleotide phosphate (NADPH) co-crystallized inhibitor. The results of the molecular docking revealed that (Z)-phytol (Ligand 39) has an affinity to interact with ctDNA sequence, and three targets Endogenous enzymes. The molecular dynamics study was conducted for the best inhibitors (Z)-phytol. A few key residues were identified at the binding site of receptors. The in-silico assessment of the ADME properties and BOILED-Egg plot reveals that compound (Z)-phytol (L39) is permeable to the blood brain barrier and have high lipophilicity and high coefficient of skin permeability in the intestines with good bioavailability. The ADMET analysis also showed that this oxygenated diterpene is safer to replace the synthetic drugs with side effects. Further testing is needed to assess its effectiveness in reducing oxidative stress for use in the pharmaceutical industry.Communicated by Ramaswamy H. Sarma.

(-)-Epigallocatechin-3-Gallate Diminishes Intra-and Extracellular Amyloid-Induced Cytotoxic Effects on Cholinergic-like Neurons from Familial Alzheimer's Disease PSEN1 E280A

Alzheimer’s disease (AD) is a complex neurodegenerative disease characterized by functional disruption, death of cholinergic neurons (ChNs) because of intracellular and extracellular Aβ aggregates, and hyperphosphorylation of protein TAU (p-TAU). To date, there are no efficient therapies against AD. Therefore, new therapies for its treatment are in need. The goal of this investigation was to evaluate the effect of the polyphenol epigallocatechin-3-gallate (EGCG) on cholinergic-like neurons (ChLNs) bearing the mutation E280A in PRESENILIN 1 (PSEN1 E280A). To this aim, wild-type (WT) and PSEN1 E280A ChLNs were exposed to EGCG (5–50 μM) for 4 days. Untreated or treated neurons were assessed for biochemical and functional analysis. We found that EGCG (50 μM) significantly inhibited the aggregation of (i)sAPPβf, blocked p-TAU, increased ∆Ψm, decreased oxidation of DJ-1 at residue Cys106-SH, and inhibited the activation of transcription factor c-JUN and P53, PUMA, and CASPASE-3 in mutant ChLNs compared to WT. Although EGCG did not reduce (e)Aβ42, the polyphenol reversed Ca²⁺ influx dysregulation as a response to acetylcholine (ACh) stimuli in PSEN1 E280A ChLNs, inhibited the activation of transcription factor NF-κB, and reduced the secretion of pro-inflammatory IL-6 in wild-type astrocyte-like cells (ALCs) when exposed to mutant ChLNs culture supernatant. Taken together, our findings suggest that the EGCG might be a promising therapeutic approach for the treatment of FAD.

Epigallocatechin-3-Gallate Promotes the in vitro Maturation and Embryo Development Following IVF of Porcine Oocytes

Purpose

Epigallocatechin-3-gallate (EGCG) is a major ingredient of catechin polyphenols and exerts protective effects because of its strong antioxidant properties. As far as we know, there is still a lack of systematic research on the effects of EGCG on the in vitro maturation (IVM) and in vitro fertilization (IVF) of porcine oocytes. The present study aimed to determine the effects of EGCG on the IVM and IVF of porcine oocytes.

Methods

Porcine oocytes were treated with different concentrations of EGCG (5, 10 and 20 µM), and the cumulus cell expansion, oocyte maturation rate, reactive oxygen species (ROS), glutathione (GSH) and malondialdehyde (MDA) levels, total antioxidant capacity were determined. The mRNA expression levels of oxidative stress- and apoptosis-associated genes were determined by quantitative real-time PCR. The cleavage rate and blastocyst rate of oocytes after 10 μM EGCG treatment during IVM and IVF were also evaluated.

Results

EGCG at 5, 10 and 20 μM significantly promoted cumulus cell expansion, and EGCG at 10 μM increased the oocyte maturation rate. EGCG (10 μM) treatment reduced the ROS and MDA levels, while increased the antioxidant capacity and GSH concentrations in the mature oocytes. The qRT-PCR results showed that EGCG treatment up-regulated the mRNA expression of catalase, glutathione peroxidase and superoxide dismutase in the mature oocytes. In addition, EGCG treatment also decreased the mRNA expression levels of Bax and caspase-3 and increased the Bcl-2 mRNA expression level in the mature oocytes. In addition, the cleavage rate and blastocyst rate of oocytes treated with 10 μM EGCG during IVM and IVF were significantly higher than those of the control group.

Conclusion

Our results suggest that EGCG promotes the in vitro maturation and embryo development following IVF of porcine oocytes. The protective effects of EGCG on the oocytes may be associated with its antioxidant and anti-apoptosis properties.

Caveolin-1 promotes radioresistance in rhabdomyosarcoma through increased oxidative stress protection and DNA repair

The aim of this work was to investigate whether Caveolin-1 (Cav-1), a membrane scaffolding protein widely implicated in cancer, may play a role in radiation response in rhabdomyosarcoma (RMS), a pediatric soft tissue tumor. For this purpose, we employed human RD cells in which Cav-1 expression was stably increased via gene transfection. After radiation treatment, we observed that Cav-1 limited cell cycle arrest in the G2/M phase and enhanced resistance to cell senescence and apoptosis via reduction of p21^Cip1/Waf1, p16^INK4a and Caspase-3 cleavage. After radiotherapy, Cav-1-mediated cell radioresistance was characterized by low accumulation of H2AX foci, as confirmed by Comet assay, marked neutralization of reactive oxygen species (ROS) and enhanced DNA repair via activation of ATM, Ku70/80 complex and DNA-PK. We found that Cav-1-overexpressing RD cells, already under basal conditions, had higher glutathione (GSH) content and greater catalase expression, which conferred protection against acute treatment with hydrogen peroxide. Furthermore, pre-treatment of Cav-1-overexpressing cells with PP2 or LY294002 compounds restored the sensitivity to radiation treatment, indicating a role for Src-kinases and Akt pathways in Cav-1-mediated radioresistance. These findings were confirmed using radioresistant RD and RH30 lines generated by hypofractionated radiotherapy protocol, which showed marked increase of Cav-1, catalase and Akt, and sensitivity to PP2 and LY294002 treatment. In conclusion, these data suggest that concerted activity of Cav-1 and catalase, in cooperation with activation of Src-kinase and Akt pathways, may represent a network of vital mechanisms that allow irradiated RMS cells to evade cell death induced by oxidative stress and DNA damage.

Iron Complexes of Flavonoids-Antioxidant Capacity and Beyond

Flavonoids are common plant natural products able to suppress ROS-related damage and alleviate oxidative stress. One of key mechanisms, involved in this phenomenon is chelation of transition metal ions. From a physiological perspective, iron is the most significant transition metal, because of its abundance in living organisms and ubiquitous involvement in redox processes. The chemical, pharmaceutical, and biological properties of flavonoids can be significantly affected by their interaction with transition metal ions, mainly iron. In this review, we explain the interaction of various flavonoid structures with Fe(II) and Fe(III) ions and critically discuss the influence of chelated ions on the flavonoid biochemical properties. In addition, specific biological effects of their iron metallocomplexes, such as the inhibition of iron-containing enzymes, have been included in this review.

Solid Lipid Microparticles for Oral Delivery of Catalase: Focus on the Protein Structural Integrity and Gastric Protection

Protein inactivation either during the production process or along the gastrointestinal tract is the major problem associated with the development of oral delivery systems for biological drugs. This work presents an evaluation of the structural integrity and the biological activity of a model protein, catalase, after its encapsulation in glyceryl trimyristate-based solid lipid microparticles (SLMs) obtained by the spray congealing technology. Circular dichroism and fluorescence spectroscopies were used to assess the integrity of catalase released from SLMs. The results confirmed that no conformational change occurred during the production process and both the secondary and tertiary structures were retained. Catalase is highly sensitive to temperature and undergoes denaturation above 60 °C; nevertheless, spray congealing allowed the retention of most biological activity due to the loading of the drug at the solid state, markedly reducing the risk of denaturation. Catalase activity after exposure to simulated gastric conditions (considering both acidic pH and the presence of gastric digestive hydrolases) ranged from 35 to 95% depending on the carrier: increasing of both the fatty acid chain length and the degree of substitution of the glyceride enhanced residual enzyme activity. SLMs allowed the protein release in a simulated intestinal environment and were not cytotoxic against HT29 cells. In conclusion, the encapsulation of proteins into SLMs by spray congealing might be a promising strategy for the formulation of nontoxic and inexpensive oral biotherapeutic products.

A review for physiological activities of EGCG and the role in improving fertility in humans/mammals

Epigallocatechin-3-gallate (EGCG) is a secondary metabolite in green tea, which has various physiological activities, including antioxidant, antitumor, and antiviral activities. Studies have shown that EGCG has a preventive effect on infertility by protecting germ cells and oocytes from damage. EGCG functions mainly through the regulation of ROS (reactive oxygen species) levels, which affect the expression of catalase (CAT), superoxide dismutase 1(SOD1), superoxide dismutase 2(SOD2), and glutathione peroxidase (GPx), has positive influence on other enzyme activities in germ cells and oocytes, and actively alters antioxidant activities. These enzymes above can inhibit the activation of extracellular signal-regulated proteins (Erk), induce apoptosis, and control the production of ROS in tissue cells. Here, we present a comprehensive overview of the mechanisms underlying the main physiological activities of EGCG, including antioxidant, antitumor, and antiviral activities, and their potential roles in male and female reproductive systems and fertility. This paper discusses the mechanisms by which EGCG retards the infertility of germ cells and oocytes and provides a supportive recommendation for improving fertility in humans and animals. We hope it will provide useful references for related research in mammalian reproduction.

Redox reactions of heme proteins with flavonoids

Proteins containing heme groups perform a variety of important functions in living organisms. The heme groups are involved in catalyzing oxidation/reduction reactions, in electron transfer, and in binding small molecules, like oxygen or nitric oxide. Flavonoids, low molecular weight plant polyphenols, are ubiquitous components of human diet. They are also components of many plant extracts used in herbal medicine as well as of food supplements. Due to their relatively low reduction potential, flavonoids are prone to oxidation. This paper provides a review of redox reactions of various heme proteins, including catalase, some peroxidases, cytochrome P450, cytochrome c, myoglobin, and hemoglobin with flavonoids. Potential biological significance of these reactions is discussed, in particular when flavonoids are delivered to the body at pharmacological doses.

Interaction of Catechins with Human Erythrocytes

The aim of this study was to characterize the interaction of chosen catechins ((+)-catechin, (−)-epigallocatechin (EGC), and (−)-epigallocatechin gallate (EGCG)) with human erythrocytes and their protective effects against oxidative damage of erythrocytes. Uptake of the catechins by erythrocytes was studied by fluorimetry, their interaction with erythrocyte membrane was probed by changes in erythrocyte osmotic fragility and in membrane fluidity evaluated with spin labels, while protection against oxidative damage was assessed by protection against hemolysis induced by permanganate and protection of erythrocyte membranes against lipid peroxidation and protein thiol group oxidation. Catechin uptake was similar for all the compounds studied. Accumulation of catechins in the erythrocyte membrane was demonstrated by the catechin-induced increase in osmotic resistance and rigidification of the erythrocyte membrane detected by spin labels 5-doxyl stearic acid and 16-doxyl stearic acid. (−)-Epigallocatechin and EGCG inhibited erythrocyte acetylcholinesterase (mixed-type inhibition). Catechins protected erythrocytes against permanganate-induced hemolysis, oxidation of erythrocyte protein thiol groups, as well as membrane lipid peroxidation. These results contribute to the knowledge of the beneficial effects of catechins present in plant-derived food and beverages.

Preclinical Pharmacological Activities of Epigallocatechin-3-gallate in Signaling Pathways: An Update on Cancer

Epigallocatechin gallate (EGCG) is the main bioactive component of catechins predominantly present in svarious types of teas. EGCG is well known for a wide spectrum of biological activity as an anti-oxidative, anti-inflammatory, and anti-tumor agent. The effect of EGCG on cell death mechanisms via the induction of apoptosis, necrosis, and autophagy has been documented. Moreover, its anti-proliferative and chemopreventive action has been demonstrated in many cancer cell lines. It was also involved in the modulation of cyclooxygenase-2, in oxidative stress and inflammation of different cell processes. EGCG has been reported as a promising target for plasma membrane proteins, such as epidermal growth factor receptor (EGFR). In addition, it has been demonstrated a mechanism of action relying on the inhibition of ERK1/2, p38 MAPK, NF-κB, and vascular endothelial growth factor (VEGF). EGCG and its derivatives were used in proteasome inhibition and they were involved in epigenetic mechanisms. In summary, EGCG is the most predominant and bioactive constituent of teas and it has a pivotal role in cancer prevention. Its preclinical pharmacological activities are associated with complex molecular mechanisms that involve numerous signaling pathways.

EGCG regulates CTR1 expression through its pro-oxidative property in non-small-cell lung cancer cells

Copper transporter 1 (CTR1) plays an important role in increasing cisplatin intake. Our previous studies showed that CTR1 expression was upregulated by (-)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol, therefore enhanced cisplatin sensitivity in ovary cancer and non-small-cell lung cancer (NSCLC) cells. In the current study in the non-small-cell lung cancer cells, we uncovered a potential mechanism of EGCG-induced CTR1 through its pro-oxidative property. We found that EGCG increased reactive oxygen species (ROS) generation, while in the presence of ROS scavenger N-acetyl-cysteine (NAC), ROS production was eliminated. Changes of CTR1 expression were consistent with the ROS level. Simultaneously, EGCG downregulated ERK1/2 while upregulated lncRNA nuclear paraspeckle assembly transcript 1 (NEAT1) through ROS to induce CTR1 expression. Besides, in a nude mouse xenografts model, EGCG treatment raised ROS level, expression of CTR1 and NEAT1 in tumor tissue. Also, ERK1/2 and p-ERK1/2 were suppressed as well. Taken together, these results suggested a novel mechanism that EGCG mediated ROS to regulate CTR1 expression through the ERK1/2/NEAT1 signaling pathway, which provided more possibilities for EGCG as a natural agent in adjuvant therapy of lung cancer.

Physicochemical characterization of dual action liposomal formulations: anticancer and antimicrobial

BACKGROUND

Cancer till date remains one of the world's most life threatening disease accompanied by risk of secondary infections. Therefore formulations carrying anticancer drugs which can also decrease the risk of secondary infection are inevitable. Chemotherapeutic drug doxorubicin along with flavonoids quercetin and epigallocatechin gallate (EGCG) is simultaneously loaded on liposomal formulation exploiting the amphiphilic property of the liposomes.

RESULTS

Atomic force microscope imaging reveal the size of liposomal formulation loaded with doxorubicin, quercetin and EGCG to be greater than void liposome confirming the presence of drugs. Liposomal stability is improved by PEGylation; adding to the drug release time in vitro. The charge of phosphatidylcholine is rendered positive by coating the formulation with histone. The average size of the formulation is 342 nm. The encapsulation efficiency of doxorubicin, quercetin and EGCG is found to be 65.8%, 96.8% and 98% respectively. The above formulation demonstrated both anticancer and antimicrobial activity.

CONCLUSION

The formulation will provide dual anticancer and antimicrobial therapy thereby evading secondary infection in cancer patients along with chemotherapy.

Chemo-preventive and therapeutic effect of the dietary flavonoid kaempferol: A comprehensive review

Kaempferol, a natural flavonoid present in several plants, possesses a wide range of therapeutic properties such as antioxidant, anticancer, and anti-inflammatory. It has a significant role in reducing cancer and can act as a therapeutic agent in the treatment of diseases and ailments such as diabetes, obesity, cardiovascular diseases, oxidative stress, asthma, and microbial contamination disorders. Kaempferol acts through different mechanisms: It induces apoptosis (HeLa cervical cancer cells), decreases cell viability (G2/M phase), downregulates phosphoinositide 3-kinase (PI3K)/AKT (protein kinase B) and human T-cell leukemia/lymphoma virus-I (HTLV-I) signaling pathways, suppresses protein expression of epithelial-mesenchymal transition (EMT)-related markers including N-cadherin, E-cadherin, Slug, and Snail, and metastasis-related markers such as matrix metallopeptidase 2 (MMP-2). Accordingly, the aim of the present review is to collect information pertaining to the effective role of kaempferol against various degenerative disorders, summarize the antioxidant, anti-inflammatory, anticancer, antidiabetic, and antiaging effects of kaempferol and to review the progress of recent research and available data on kaempferol as a protective and chemotherapeutic agent against several ailments.

In Vitro and In Silico Studies of the Molecular Interactions of Epigallocatechin-3-O-gallate (EGCG) with Proteins That Explain the Health Benefits of Green Tea

Green tea has been shown to have beneficial effects on many diseases such as cancer, obesity, inflammatory diseases, and neurodegenerative disorders. The major green tea component, epigallocatechin-3-O-gallate (EGCG), has been demonstrated to contribute to these effects through its anti-oxidative and pro-oxidative properties. Furthermore, several lines of evidence have indicated that the binding affinity of EGCG to specific proteins may explain its mechanism of action. This review article aims to reveal how EGCG-protein interactions can explain the mechanism by which green tea/EGCG can exhibit health beneficial effects. We conducted a literature search, using mainly the PubMed database. The results showed that several methods such as dot assays, affinity gel chromatography, surface plasmon resonance, computational docking analyses, and X-ray crystallography have been used for this purpose. These studies have provided evidence to show how EGCG can fit or occupy the position in or near functional sites and induce a conformational change, including a quaternary conformational change in some cases. Active site blocking, steric hindrance by binding of EGCG near an active site or induced conformational change appeared to cause inhibition of enzymatic activity and other biological activities of proteins, which are related to EGCG’s biological oligomer and formation of their toxic aggregates, leading to the prevention of neurodegenerative diseases and amyloidosis. In conclusion, these studies have provided useful information on the action of green tea/catechins and would lead to future studies that will provide further evidence for rational EGCG therapy and use EGCG as a lead compound for drug design.

The antiproliferative activity of di-2-pyridylketone dithiocarbamate is partly attributed to catalase inhibition: detailing the interaction by spectroscopic methods

The bioactivity of drugs is attributed to their interaction with biological molecules, embodied in either their direct or indirect influence on enzyme activity and conformation. Di-2-pyridylketone hydrazine dithiocarbamate (DpdtC) exhibits significant antitumor activity in our preliminary study. We speculated that its activity may partly stem from enzyme inhibition due to strong metal chelating ability. To this end, we assessed its effect on catalase from erythrocytes and found evidence of inhibition, which was further confirmed by ROS determination in vivo. Thus, detailing the interaction between the agent and catalase via spectroscopic methods and molecular docking was required to obtain information on both the dynamics and thermodynamic parameters. The Lineweaver-Burk plot implied an uncompetitive pattern between DpdtC and catalase from beef liver, and IC₅₀ = ∼7 μM. The thermodynamic parameters from fluorescence quenching measurements indicated that DpdtC could bind to catalase with moderate affinity (K_a = approximately 10⁴ M^-1). CD spectra revealed that DpdtC could significantly disrupt the secondary structure of catalase. Docking studies indicated that DpdtC bound to a flexible region of catalase, involving hydrogen bonds and salt bond; this was consistent with thermodynamic results from spectral investigations. Our data clearly showed that catalase inhibition of DpdtC was not due to direct chelation of iron from heme (killing), but through an allosteric effect. Thus, it can be concluded that the antiproliferative activity of DpdtC is partially attributed to its catalase inhibition.

Alterations of mitochondrial electron transport chain and oxidative stress induced by alkaloid-like α-aminonitriles on Aedes aegypti larvae

Aedes aegypti mosquitoes are responsible for dengue, chikungunya, and Zika virus transmission in tropical and subtropical areas around the world. Due to the absence of vaccines or antiviral drugs for human treatment, the majority of control strategies are targeted at Ae. aegypti elimination. Our research on mosquito control insecticidal agents has previously shown that the alkaloid girgensohnine and its analogues (α-aminonitriles) present in vitro acetylcholinesterase inhibition and in vivo insecticidal activity against Ae. aegypti. However, acetylcholinesterase inhibition may not be the only mechanism of action behind these effects. On this basis, the principal aim of this study was to elucidate the possible action mode of four α-aminonitriles on Ae. aegypti by studying other important enzymatic targets, such as mitochondrial electron transport chain complexes, catalase, and superoxide dismutase, key oxidative stress enzymes. Mitochondria were isolated from Ae. aegypti larvae by differential centrifugation, stored at -70°C, and fragmented using ultrasound for 10min. The effects of α-aminonitriles (1 to 4) over enzymatic activities were evaluated using concentrations of 8nM, 2μM, 8μM, and 40μM. Results indicated that α-aminonitriles caused significant NADH dehydrogenase and succinate oxidase inhibition (~44% at the highest concentration tested). Succinate dehydrogenase and cytochrome c oxidase activities were found to increase (162% and 106% at 40μM, respectively). It was also observed that these compounds produced catalase inhibition and thus prevented H₂O₂ reduction, which induced the formation of reactive oxygen species (ROS). Moreover, NBT assay showed that compounds 3 and 4 (with 2-(pyrrolidin-1-yl) acetonitrile as substituent) increased by approximately 50% the O₂^●- concentration in the mitochondrial respiratory chain. It was concluded that the tested compounds act as complex I inhibitors by blocking electron transport and causing electron leak, possibly between complex I and III. Furthermore, α-aminonitriles inhibited catalase activity; compounds 1 and 2 (with piperidine fragment) inhibited glutathione reductase activity and further promoted the accumulation of ROS, which probably induced oxidative stress.

Inhibition of cancer antioxidant defense by natural compounds

All classic, non-surgical anticancer approaches like chemotherapy, radiotherapy or photodynamic therapy kill cancer cells by inducing severe oxidative stress. Even tough chemo- and radiotherapy are still a gold standard in cancer treatment, the identification of non-toxic compounds that enhance their selectivity, would allow for lowering their doses, reduce side effects and risk of second cancers. Many natural products have the ability to sensitize cancer cells to oxidative stress induced by chemo- and radiotherapy by limiting antioxidant capacity of cancer cells. Blocking antioxidant defense in tumors decreases their ability to balance oxidative insult and results in cell death. Though one should bear in mind that the same natural compound often exerts both anti-oxidant and pro-oxidant properties, depending on concentration used, cell type, exposure time and environmental conditions. Here we present a comprehensive overview of natural products that inhibit major antioxidant defense mechanisms in cancer cells and discuss their potential in clinical application.

Catalase inhibition an anti cancer property of flavonoids: A kinetic and structural evaluation

Flavonoids are dietary polyphenols that present abundantly in fruits and vegetables. Flavonoids have inhibitory effects on enzymes and catalase is one among them. Catalase is a common enzyme ubiquitously found in all living organisms exposed to oxygen. It catalyzes the decomposition of hydrogen peroxide to water and oxygen (2H₂O₂→2H₂O+O₂)_. Inhibition of pure and cellular catalase from K562 cells by flavonoids was similar and exhibited the following efficacy; Myrecetin>Quercetin>Kaempferol and Quercetin>Luteolin>Apigenin demonstrating structure activity relationship. Circular Dichroism (CD) spectra have shown distinct loss in α-helical structure of the catalase on interaction with the flavonoids. All flavonoids inhibited the catalase activity by uncompetitive mechanism. The K_m and V_max values of pure catalase were observed to be 294mM^-1 and 0.222mM^-1s^-1 respectively and on inhibition with myrecetin the values decreased to a minimum of 23mM^-1 and 0.014mM^-1s^-1 respectively. Inhibition of catalase will directly results in increased production of Reactive Oxygen Species (ROS) and pro-oxidant property of flavonoids. This inhibition was reversed in presence of Cu²⁺ ions because of the chelating affect of flavonoids.

Characterization of Active Anthocyanin Degradation in the Petals of Rosa chinensis and Brunfelsia calycina Reveals the Effect of Gallated Catechins on Pigment Maintenance

Anthocyanin degradation decreases ornamental or nutritional values of horticultural products. To investigate factors that may influence colour change in flower development, anthocyanin degradation was compared between the flowers of Brunfelsia calycina and Rosa chinensis, which show rapid and slow degradation, respectively. In-gel activity assays, high performance liquid chromatography (HPLC) analysis of tannins, enzyme kinetics measurement and immune-detection of anthocyanin degradation related-perioxidases (PODs) were carried out for the comparison. Rose petals possessed significantly lower anthocyanin degradation-related POD activities than Brunfelsia petals, which may be related to the high tannin contents. Epicatechin gallate (ECG) and gallocatechin gallate (GCG) were detected in rose as 161.3 ± 12.34 and 273.56 ± 41.23 μg/g FW (Fresh Weight) respectively, while not detected in Brunfelsia. ECG and GCG inhibited the activities of the Brunfelsia POD with half maximal inhibitory concentrations (IC50s) as 21.5 and 29.7 μM respectively, and increased the colour intensities of the anthocyanins. Catechin and epicatechin did not inhibit the POD activity, while serving as POD substrates, with Km (the Michaelis constant) as 0.48 and 1.23 mM. Similar protein levels of the anthocyanin degradation-related 40-kDa PODs were detected in Brunfelsia and rose. In summary, high amount of tannins, particularly ECG and GCG, in red rose petals may inhibit the degradation-related enzymes, leading to the maintenance of anthocyanins in vivo.

Development of an assay to assess genotoxicity by particulate matter extract

The current study describes a method for assessing the oxidative potential of common environmental stressors (ambient air particulate matter), using a plasmid relaxation assay where the extract caused single-strand breaks, easily visualised through electrophoresis. This assay utilises a miniscule amount (11 µg) of particulate matter (PM) extract compared to other, cell-based methods (~3,000 µg). The negative impact of air pollution on human health has been extensively recognised. Among the air pollutants, PM plays an eminent role, as reflected in the broad scientific interest. PM toxicity highly depends on its composition (metals and organic compounds), which in turn has been linked to multiple health effects (such as cardiorespiratory diseases and cancer) through multiple toxicity mechanisms; the induction of oxidative stress is considered a major mechanism among these. In this study, the PM levels, oxidative potential, cytotoxicity and genotoxicity of PM in the region of Larissa, Greece were examined using the plasmid relaxation assay. Finally, coffee extracts from different varieties, derived from both green and roasted seeds, were examined for their ability to inhibit PM-induced DNA damage. These extracts also exerted an inhibitory effect on xanthine oxidase and catalase, but had no effect against superoxide dismutase. Overall, this study highlights the importance of assays for assessing the oxidative potential of widespread environmental stressors (PM), as well as the antioxidant capacity of beverages and food items, with the highlight being the development of a plasmid relaxation assay to assess the genotoxicity caused by PM using only a miniscule amount.

Application of isothermal titration calorimetry as a tool to study natural product interactions

The study of molecular interactions of natural products by isothermal titration calorimetry (ITC) is a potent tool to get new insights of the underpinning driving forces.

Gold-conjugated green tea nanoparticles for enhanced anti-tumor activities and hepatoprotection--synthesis, characterization and in vitro evaluation

Green tea (GT)-based chemoprevention has shown promising results in various cancer models. However, the effective dose may not be far from the toxic dose because of inefficient systemic delivery and limited bio-availability of GT polyphenols. We have used GT polyphenols to successfully reduce gold to corresponding gold nanoparticles (NPs) in a single step; a process that fulfils all criteria of green nanotechnology as no "man-made" chemical other than gold acids are used. GT and (-) - epigallocatechin-3-gallate (EGCG) conjugated gold NPs (diameters <50 nm), showed remarkable stability, significantly rapid cellular uptake and excellent in vitro anti-oxidant activities. These NPs were observed to be selectively toxic towards cancer cells (Ehrlich's Ascites Carcinoma and MCF-7) while showing absolutely no lethality towards normal primary mouse hepatocytes. In cancer cells, NPs altered the redox status and limited Nrf2 activation by almost 50%. These NPs significantly decreased nuclear translocation of NF-κB, coupled with decreased phosphorylation of IĸB and down-regulation of NF-κB-dependent anti-apoptotic proteins Bcl2 and Akt in a dose-dependent manner, triggering onset of apoptosis. Culturing normal hepatocytes with tumor-conditioned media prompted apoptosis by increasing reactive oxygen species (ROS) and depleting the anti-oxidant defense mechanism of hepatocytes. Pre-treatment with NPs protected hepatocytes from tumor-induced cellular damage by scavenging excess ROS, increasing the levels of reduced glutathione and anti-oxidant enzymes. There was evidence of decreased Bax/Bcl2 ratio and active Caspase 3 levels in these hepatocytes, indicating apoptosis escape. Nanoformulations of GT-based polyphenols might serve as an operative platform for effective delivery, increased bio-availability, enhanced effects and minimal chemotherapy-associated toxicities.