Characteristics of juglone (5-hydroxy-1,4,-naphthoquinone) using voltammetry and spectrophotometric methods

The protective role of 5-hydroxy-1,4-naphthoquinone against the harmful effects of 50 Hz electric field in rat lung tissue

There is strong scientific evidence that the electric field is harmful to life. Exposure to an electric field (EF) can cause lung toxicity and respiratory disorders. In addition, the electric field has been shown to cause tissue damage through inflammation and apoptosis. Juglone (JUG) is one of the powerful antioxidants with anti-apoptotic and anti-inflammatory, various pharmacological properties in the biological system. In this study, we evaluated the efficacy of JUG against the potential adverse effects of electric field on the lung. Twenty-four Wistar albino rats were randomly divided into three groups; control group (Cont), EF group, and EF exposure+JUG-treated group (EJUG). After routine histological procedures, sections stained with hematoxylin-eosin (H&E) showed significant changes in lung tissues in the EF group compared to the Cont group. Significant protective effects were observed in the building volumes and histopathology in the EJUG group. Our immunohistochemical and gene expression results increased the expression of caspase-3 and tumor necrosis factor alpha (TNF-α) in the EF group (p < 0.05). Juglon increased cytokine signal suppressor (SOCS) expression (p < 0.001). These findings were consistent with the antioxidant effect of JUG treatment. We reasoned that exposure to EF damaged rat lung tissues and administration of JUG alleviated the complications caused by 50 Hz EF.

Comparative Methods to Evaluate the Antioxidant Capacity of Propolis: An Attempt to Explain the Differences

Propolis is a natural product produced by bees that contains a complex mixture of compounds, including phenolic compounds and flavonoids. These compounds contribute to its biological activities, such as antioxidant capacity. This study analysed the pollen profile, total phenolic content (TPC), antioxidant properties, and phenolic compound profile of four propolis samples from Portugal. The total phenolic compounds in the samples were determined by six different techniques: four different Folin-Ciocalteu (F-C) methods, spectrophotometry (SPECT), and voltammetry (SWV). Of the six methods, SPECT allowed the highest quantification, while SWV achieved the lowest. The mean TPC values for these methods were 422 ± 98 and 47 ± 11 mg GAE/g sample, respectively. Antioxidant capacity was determined by four different methods: DPPH, FRAP, original ferrocyanide (OFec), and modified ferrocyanide (MFec). The MFec method gave the highest antioxidant capacity for all samples, followed by the DPPH method. The study also investigated the correlation between TPC and antioxidant capacity with the presence of hydroxybenzoic acid (HBA), hydroxycinnamic acid (HCA), and flavonoids (FLAV) in propolis samples. The results showed that the concentrations of specific compounds in propolis samples can significantly impact their antioxidant capacity and TPC quantification. Analysis of the profile of phenolic compounds by the UHPLC-DAD-ESI-MS technique identified chrysin, caffeic acid isoprenyl ester, pinocembrin, galangin, pinobanksin-3-O-acetate, and caffeic acid phenyl ester as the major compounds in the four propolis samples. In conclusion, this study shows the importance of the choice of method for determining TPC and antioxidant activity in samples and the contribution of HBA and HCA content to their quantification.

Sustainable Synthesis, Antiproliferative and Acetylcholinesterase Inhibition of 1,4- and 1,2-Naphthoquinone Derivatives

This work describes the design, sustainable synthesis, evaluation of electrochemical and biological properties against HepG2 cell lines, and AChE enzymes of different substituted derivatives of 1,4- and 1,2-naphthoquinones (NQ). A microwave-assisted protocol was optimized with success for the synthesis of the 2-substituted-1,4-NQ series and extended to the 4-substituted-1,2-NQ family, providing an alternative and more sustainable approach to the synthesis of naphthoquinones. The electrochemical properties were studied by cyclic voltammetry, and the redox potentials related to the molecular structural characteristics and the biological properties. Compounds were tested for their potential anti-cancer activity against a hepatocellular carcinoma cell line, HepG2, using MTT assay, and 1,2-NQ derivatives were found to be more active than their 1,4-NQ homologues (3a-f), with the highest cytotoxic potential found for compound 4a (EC₅₀ = 3 μM). The same trend was found for the inhibitory action against acetylcholinesterase, with 1,2-NQ derivatives showing higher inhibition_50µM than their 1,4-NQ homologues, with 4h being the most potent compound (Inhibition_50µM = 85%). Docking studies were performed for the 1,2-NQ derivatives with the highest inhibitions, showing dual binding interactions with both CAS and PAS sites, while the less active 1,4-NQ derivatives showed interactions with PAS and the mid-gorge region.

Polymeric Forms of Plant Flavonoids Obtained by Enzymatic Reactions

Naringenin is one of the flavonoids originating from citrus fruit. This polyphenol is mainly found in grapefruit, orange and lemon. The antioxidant and antimicrobial properties of flavonoids depend on their structure, including the polymeric form. The aim of this research was to achieve enzymatic polymerization of naringenin and to study the properties of poly(naringenin). The polymerization was performed by methods using two different enzymes, i.e., laccase and horseradish peroxidase (HRP). According to the literature data, naringenin had not been polymerized previously using the enzymatic polymerization method. Therefore, obtaining polymeric naringenin by reaction with enzymes is a scientific novelty. The research methodology included analysis of the structure of poly(naringenin) by NMR, GPC, FTIR and UV-Vis and its morphology by SEM, as well as analysis of its properties, i.e., thermal stability (DSC and TGA), antioxidant activity (ABTS, DPPH, FRAP and CUPRAC) and antimicrobial properties. Naringenin oligomers were obtained as a result of polymerization with two types of enzymes. The polymeric forms of naringenin were more resistant to thermo-oxidation; the final oxidation temperature T_o of naringenin catalyzed by laccase (poly(naringenin)-laccase) was 28.2 °C higher, and poly(naringenin)-HRP 23.6 °C higher than that of the basic flavonoid. Additionally, due to the higher molar mass and associated increase in OH groups in the structure, naringenin catalyzed by laccase (poly(naringenin)-laccase) showed better activity for scavenging ABTS^+• radicals than naringenin catalyzed by HRP (poly(naringenin)-HRP) and naringenin. In addition, poly(naringenin)-laccase at a concentration of 5 mg/mL exhibited better microbial activity against E. coli than monomeric naringenin.

Characteristics of the Polyphenolic Profile and Antioxidant Activity of Cone Extracts from Conifers Determined Using Electrochemical and Spectrophotometric Methods

The aim of the study was to analyze the polyphenolic profile of cone extracts of Douglas fir, Scots pine and Korean fir, and to study their antioxidant activity. The mechanism of electro-oxidation of polyphenols (such as procyanidins and catechins) from cone extracts was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), as well as spectrophotometric methods-ABTS (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate)), DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power ) and CUPRAC (CUPric Reducing Antioxidant Capacity). The scientific novelty of the research is the comprehensive analysis of cone extracts in terms of antioxidant properties. Due to the high polyphenol content, the extracts showed significant ability to reduce oxidative reactions, as well as the ability to scavenge free radicals and transition metal ions. Douglas fir, Scots pine and Korean fir cone extracts can potentially be used as natural stabilizers, preservatives and antimicrobial substances in the food industry and in medications.

Biocomposites of Epoxidized Natural Rubber/Poly(Lactic Acid) Modified with Natural Substances: Influence of Biomolecules on the Aging Properties (Part II)

The aim of this study is to present the possible influence of natural substances on the aging properties of epoxidized natural rubber (ENR) and poly(lactic acid) (PLA) eco-friendly elastic blends. Therefore, the ENR/PLA blends were filled with natural pro-health substances of potentially antioxidative behavior, namely, δ-tocopherol (vitamin E), curcumin, β-carotene and quercetin. In this way, the material biodeterioration potential was maintained and the material’s lifespan was prolonged while subjected to increased temperatures or high-energy UVA irradiation (340 nm). The investigation of the samples’ properties indicated that curcumin and quercetin are the most promising natural additives that may contribute to the delay of ENR/PLA degradation under the above-mentioned conditions. The efficiency of the proposed new natural anti-aging additives was proven with static mechanical analysis, color change investigation, as well as mass loss during a certain aging. The aging coefficient, which compares the mechanical properties before and after the aging process, indicated that the ENR/PLA performance after 200 h of accelerated aging might decrease only by approximately 30% with the blend loaded with quercetin. This finding paves new opportunities for bio-based and green anti-aging systems employed in polymer technology.

Juglone prevents human platelet aggregation through inhibiting Akt and protein disulfide isomerase

BACKGROUND/PURPOSE

Juglone, a natural compound widely found in Juglandaceae plants, has been suggested as a potential drug candidate for treating cancer, inflammation, and diabetic vascular complications. In the present study, the antiplatelet effect and underlying mechanisms of juglone were investigated for the first time.

STUDY DESIGN/METHODS

Human platelet aggregation and activation were measured by turbidimetric aggregometry, flow cytometry, and Western blotting. In vitro antithrombotic activity of juglone was assessed using collagen-coated flow chambers under whole-blood flow conditions. The effect of juglone on protein disulfide isomerase (PDI) activity was determined by the dieosin glutathione disulfide assay.

RESULTS

Juglone (1 - 5 μM) inhibited platelet aggregation and glycoprotein (GP) IIb/IIIa activation caused by various agonists. In a whole blood flow chamber system, juglone reduced thrombus formation on collagen-coated surfaces under arterial shear rates. Juglone abolished intracellular Ca²⁺ elevation and protein kinase C activation caused by collagen, but had no significant effect on that induced by G protein-coupled receptor agonists. In contrast, Akt activation caused by various agonists were inhibited in juglone-treated platelets. Additionally, juglone showed inhibitory effects on both recombinant human PDI and platelet surface PDI at concentrations similar to those needed to prevent platelet aggregation.

CONCLUSION

Juglone exhibits potent in vitro antiplatelet and antithrombotic effects that are associated with inhibition of Akt activation and platelet surface PDI activity.

Novel Solid Dispersions of Naphthoquinone Using Different Polymers for Improvement of Antichagasic Activity

IVS320 (3a,10b-dihydro-1H-cyclopenta[b]naphtho[2,3-d]furan-5,10-dione) is a naphthoquinone that has low solubility in aqueous medium, a physical behavior that limits its biological activities, considering that compounds from this class have several activities. In this work, solid dispersions (SDs) prepared between IVS320 and polymers hydroxypropyl methylcellulose (HPMC), polyethylene glycol (PEG), and polyvinylpyrrolidone (PVP) were developed using physical mixture (PM), kneading (KN), and rotary evaporation (RE) methods. Dispersions were investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TG), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). In addition, in vitro antiparasitic activity in Trypanosoma cruzi Y strains was evaluated. Physical-chemical characterization demonstrated the formation of SDs through the interaction of IVS320 with polymeric matrices. SDs of IVS320-polymer presented a significant potentiation of antichagasic activity, with inhibitory growth around 62% (IVS320-HPMC/RE), 55% (IVS320-PEG/RE), and 85% (IVS320-PVP/RE), while pure IVS320 showed a value of 48% for the highest concentrations evaluated (50 µg/mL).

Antioxidant Properties of Green Coffee Extract

An infusion of green coffee is a commonly consumed beverage, famous for its health-promoting properties. Green coffee owes its properties to the richness of active phytochemicals. The aim of this study was to determine the components of green coffee bean extracts and their properties. The scope of research included gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FTIR) and Ultraviolet-Visible spectroscopy (UV-Vis) spectroscopy; the electrochemical determination of the behavior of green coffee extract; and the determination of antioxidant properties by colorimetric spectroscopic methods (ABTS, DPPH, FRAP and CUPRAC). Water and ethanol extracts from green coffee were characterized by significant antioxidant properties and a high capacity to reduce transition metal ions. Voltammetric tests showed that the solution has good antioxidant properties in view of it contains many polyphenolic compounds that oxidize in the potential range tested.

Polyphenolic Profile and Antioxidant Activity of Juglans regia L. Leaves and Husk Extracts

The aim of this study is to characterize the antioxidant capacity and establish the profile of polyphenolic compounds in walnut extracts (different extracts prepared from walnut leaf and green husks). The correlation between bioingredients of the product tested and their ability to scavenge free radicals and reduce them by chelating various metal ions were examined. Research technology combining TG (thermogravimetry), FTIR (Fourier-transform infrared spectroscopy), high-performance liquid chromatography system (HPLC) with electrochemical methods (cyclic and differential pulse voltammetry) and spectrophotometric methods (ABTS, FRAP, and DPPH assays) was used to rate the potential oxidation-reduction components of walnut extracts. A high affinity for scavenging free radicals ABTS and DPPH was found for natural substances present in leaves and green husks. The walnut is beneficial to health as it contains alpha-linolenic acid in its lipid fraction and, as demonstrated in this study, its husks are rich in polyphenolics with high antioxidant capacity.