Comparison of Antioxidant Properties of a Conjugate of Taxifolin with Glyoxylic Acid and Selected Flavonoids

Menadione Contribution to the In Vitro Radical Scavenging Potential of Phytochemicals Naringenin and Lignin

Vitamin K3 (menadione), classified as a pro-vitamin, is a synthetic form of the fat-soluble family of vitamin K compounds. The combination of the vitamin with other molecules sharing structural and/or functional similarities, such as naturally occurring polyphenols, vitamins, or biopolymers, could potentiate mutual improvement of their antioxidant activity. The aim of the present study was to evaluate the role and contribution of vitamin K3 to the in vitro radical scavenging capacity of double and triple combinations with the phytochemicals naringenin and lignin, as well as assess possible intermolecular interactions between the bioactive compounds. Comparative analyses of the DPPH and ABTS radical scavenging activity of the pure substances vitamin K3, naringenin, and lignin; the two-component systems lignin/vitamin K3 and vitamin K3/naringenin; and the triple combination vitamin K3/flavonoid/lignin were carried out. The experimental results demonstrated increased DPPH and ABTS activities of the vitamin in combination with lignin compared to those of the two pure substances, i.e., a synergistic effect was observed. The registered significant increases in the radical scavenging activity of the triple combination determined via both methods are indicative of a remarkable potentiation effect, i.e., higher antioxidant potential exceeding the additive activity of the three pure substances.

Effects of taxifolin on aspirin-induced gastric damage in rats: macroscopic and biochemical evaluation

Taxifolin (dihydroquercetin) is a flavanonol isolated from various plants and has antioxidant effects. The aim of our study was to macroscopically and biochemically investigate the effects of taxifolin on aspirin-induced oxidative gastric damage in rats and to evaluate them by comparison with those of famotidine. Rats were divided into four drug administration groups: a healthy control group, an aspirin-only group (ASG), a taxifolin + aspirin group (TASG), and a famotidine + aspirin group (FASG). The results revealed that in light of the results that we obtained, 50 mg/kg taxifolin had anti-ulcer effects. At this dose, taxifolin was able to bring COX-1 activities to a level close to those seen in healthy rats with appropriate macroscopic, oxidant/antioxidant, and biochemical parameters. Based on these results, it can be said that taxifolin may be successfully used as a more potent alternative to famotidine, which is the currently accepted treatment for aspirin-induced ulcers.

A Comparative Study of the Inhibitory Effect of Some Flavonoids and a Conjugate of Taxifolin with Glyoxylic Acid on the Oxidative Burst of Neutrophils

During the storage, processing, and digestion of flavonoid-rich foods and beverages, a condensation of flavonoids with toxic carbonyl compounds occurs. The effect of the resulting products on cells remains largely unknown. The aim of the present study was to evaluate the effects of quercetin, taxifolin, catechin, eriodictyol, hesperetin, naringenin, and a condensation product of taxifolin with glyoxylic acid on the oxidative burst of neutrophils. It was found that the flavonoids and the condensation product inhibited the total production of ROS. Flavonoids decreased both the intra and extracellular ROS production. The condensation product had no effect on intracellular ROS production but effectively inhibited the extracellular production of ROS. Thus, the condensation of flavonoids with toxic carbonyl compounds may lead to the formation of compounds exhibiting potent inhibitory effects on the oxidative burst of neutrophils. The data also suggest that, during these reactions, the influence of a fraction of flavonoids and their polyphenolic derivatives on cellular functions may change. On the whole, the results of the study provide a better understanding of the effects of polyphenols on human health. In addition, these results reveal the structure-activity relationship of these polyphenols and may be useful in a search for new therapeutic agents against diseases associated with oxidative stress.

Improving the Stability and Effectiveness of Immunotropic Squalene Nanoemulsion by Adding Turpentine Oil

Turpentine oil, owing to the presence of 7-50 terpenes, has analgesic, anti-inflammatory, immunomodulatory, antibacterial, anticoagulant, antioxidant, and antitumor properties, which are important for medical emulsion preparation. The addition of turpentine oil to squalene emulsions can increase their effectiveness, thereby reducing the concentration of expensive and possibly deficient squalene, and increasing its stability and shelf life. In this study, squalene emulsions were obtained by adding various concentrations of turpentine oil via high-pressure homogenization, and the safety and effectiveness of the obtained emulsions were studied in vitro and in vivo. All emulsions showed high safety profiles, regardless of the concentration of turpentine oil used. However, these emulsions exhibited dose-dependent effects in terms of both efficiency and storage stability, and the squalene emulsion with 1.0% turpentine oil had the most pronounced adjuvant and cytokine-stimulating activity as well as the most pronounced stability indicators when stored at room temperature. Thus, it can be concluded that the squalene emulsion with 1% turpentine oil is a stable, monomodal, and reliably safe ultradispersed emulsion and may have pleiotropic effects with pronounced immunopotentiating properties.

Interaction between Dietary Fibre and Bioactive Compounds in Plant By-Products: Impact on Bioaccessibility and Bioavailability

In Europe, around 31 million tonnes of food by-products are generated during primary production and trade. The management of these by-products may cause a negative impact, both at the economic and environmental levels, for both industry and society. In this regard, taking into consideration that these by-products retain the dietary fibre compositions and the bioactive compounds of the starting materials, plant food agro-industries have an interest in taking advantage of them, from a nutritional point of view. Therefore, this review evaluates the role of dietary fibre and bioactive compounds in these by-products as well as the potential interactions of both components and their implications for health, since the bioactive compounds associated with fibre may reach the colon, where they can be metabolised into postbiotic compounds, providing important health benefits (prebiotic, antioxidant, anti-inflammatory, etc.). Consequently, this aspect, on which there are few studies, is very relevant and must be considered in the revaluation of by-products to obtain new ingredients for food processing with improved nutritional and technological properties.

Recent Advances in Natural Polyphenol Research

Polyphenols are secondary metabolites produced by plants, which contribute to the plant's defense against abiotic stress conditions (e.g., UV radiation and precipitation), the aggression of herbivores, and plant pathogens. Epidemiological studies suggest that long-term consumption of plant polyphenols protects against cardiovascular disease, cancer, osteoporosis, diabetes, and neurodegenerative diseases. Their structural diversity has fascinated and confronted analytical chemists on how to carry out unambiguous identification, exhaustive recovery from plants and organic waste, and define their nutritional and biological potential. The food, cosmetic, and pharmaceutical industries employ polyphenols from fruits and vegetables to produce additives, additional foods, and supplements. In some cases, nanocarriers have been used to protect polyphenols during food processing, to solve the issues related to low water solubility, to transport them to the site of action, and improve their bioavailability. This review summarizes the structure-bioactivity relationships, processing parameters that impact polyphenol stability and bioavailability, the research progress in nanocarrier delivery, and the most innovative methodologies for the exhaustive recovery of polyphenols from plant and agri-waste materials.

Development of Lepidium sativum Extracts/PVA Electrospun Nanofibers as Wound Healing Dressing

Lepidium sativum L. (Garden cress/Hab El Rashad) (Ls), family Brassicaceae, has considerable importance in traditional medicine worldwide because of its antioxidant and anti-inflammatory activities. Ls fruits were used in Ayurvedic medicines as a useful drug for injuries, skin, and eye diseases. The aim of this study was to examine the effectiveness of the total ethanol extract (TEE) and polysaccharide (Poly) of Ls seeds loaded on poly(vinyl alcohol) (PVA) nanofibers (NFs) as a wound healing dressing and to correlate the activity with the constituents of each. TEE and Poly were phytochemically analyzed qualitatively and quantitatively. Qualitative analysis proved the presence of phenolic acids, flavonoids, tannins, sterols, triterpenes, and mucilage. Meanwhile, quantitative determinations were carried out spectrophotometrically for total phenolic and total flavonoid contents. High-performance liquid chromatography (HPLC) for TEE identified 15 phenolic acids and flavonoid compounds, with gallic acid and catechin as the majors. Separation, purification, and identification of the major compounds were achieved through a Puriflash system, column Sephadex LH20, and spectroscopic data (¹H, ¹³C NMR, and UV). Eight compounds (gallic acid, catechin, rutin, kaempferol-3-O-rutinoside, quercetin-3-O-rhamnoside, kaempferol-3-O-rhamnoside, quercetin, and kaempferol) were obtained. Gas-liquid chromatography (GLC) analysis for Poly identified 11 compounds, with galactose being the main. The antioxidant activity for both extracts was measured by three different methods based on different mechanisms: 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing ability of plasma (FRAP), and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS). TEE has the highest effectiveness as an antioxidant agent with IC₅₀ 82.6 ± 8.35 μg/mL for DPPH and 772.47 and 758.92 μM Trolox equivalent/mg extract for FRAP and ABTS, respectively. The PVA nanofibers (NFs) for each sample were fabricated by electrospinning. The fabricated NFs were characterized by SEM and Fourier transform infrared spectroscopy (FTIR); the results revealed successful encapsulation of TEE and Poly in the prepared NFs. Moreover, the swelling index of TEE in the prepared NFs shows that it is the most appropriate for use as a wound dressing. Cytotoxicity studies indicated a high cell viability with IC₅₀ 216 μg/mL and 1750 μg/mL for TEE and Poly, respectively. Moreover, the results revealed that nanofibers possess higher cell viability compared to solutions with the same sample quantities: 9-folds for TEE and 4-folds for Poly of amount 400 μg. The in vitro wound healing test showed that the TEE nanofibers performed better than Poly nanofibers in accelerating wound healing, with 90% for TEE, more than that for the Poly extract (82%), after 48 h. These findings implied that the incorporation of TEE in PVA nanofibers was more efficient than incorporation of Poly in improving the biological activity in wound healing. In conclusion, the TEE and polysaccharides of L. sativum L seed are ideal candidates for nanofibrous wound dressings. Furthermore, the contents of phenolic acids and flavonoids in TEE, which have potential antioxidant activity, make the TEE of L. sativum more favorable for wound healing dressing.

The effect of flavonoids on the reduction of cupric ions, the copper-driven Fenton reaction and copper-triggered haemolysis

Flavonoids are considered beneficial, but they may exhibit pro-oxidative effects likely due to metal reducing properties. For the first time, 24 structurally related flavonoids were compared for copper reduction, and modulation of the copper-triggered Fenton reaction and lysis of erythrocytes. The vast majority of flavonoids reduced cupric ions; their behaviour ranged from progressive gradual reduction through bell-shaped, neutral, to a blockade of spontaneous reduction. Similarly, different behaviours were observed with the Fenton reaction. Flavone was the only flavonoid that potentiated copper-triggered haemolysis (155 ± 81 % at twice the amount of Cu²⁺), while 18 flavonoids were at least partly protective in some concentrations. Only 5-hydroxyflavone did not reduce Cu²⁺ and behaved as an antioxidant in both assays (reduction of 60 ± 10 % and 88 ± 1%, respectively, at an equimolar ratio with Cu²⁺). In conclusion, relatively subtle structural differences resulted in very different anti/prooxidant behaviour depending on the model.

(±)-Catechin—A Mass-Spectrometry-Based Exploration Coordination Complex Formation with FeII and FeIII

Catechin is an extensively investigated plant flavan-3-ol with a beneficial impact on human health that is often associated with antioxidant activities and iron coordination complex formation. The aim of this study was to explore these properties with FeII and FeIII using a combination of nanoelectrospray-mass spectrometry, differential pulse voltammetry, site-specific deoxyribose degradation assay, FeII autoxidation assay, and brine shrimp mortality assay. Catechin primarily favored coordination complex formation with Fe ions of the stoichiometry catechin:Fe in the ratio of 1:1 or 2:1. In the detected Fe–catechin coordination complexes, FeII prevailed. Differential pulse voltammetry, the site-specific deoxyribose degradation, and FeII autoxidation assays proved that coordination complex formation affected catechin’s antioxidant effects. In situ formed Fe–catechin coordination complexes showed no toxic activities in the brine shrimp mortality assay. In summary, catechin has properties for the possible treatment of pathological processes associated with ageing and degeneration, such as Alzheimer’s and Parkinson’s diseases.

Isolation, identification, and activity evaluation of antioxidant components from Inula viscosa: A bioguided approach

Oxidative stress is linked to several invasive diseases which causes significant clinical and economic impact, therefore, there is a need to develop new antioxidants. The natural products could play an important role in overcoming the current need. In the present work, the antioxidant bioassay-guided fractionation of the ethanolic extract of Inula viscosa leaves (Asteraceae) was performed using DPPH and ABTS assays affording three known compounds, which were successfully characterized as ilicic acid (1), taxifolin (2) and quercetin (3) based on 1D, 2D NMR. Compounds 2 and 3 were identified as the most active, displaying similar or higher potency against ABTS (value 41.27 for quercetin and 142.58 for taxifolin) and similar activity against DPPH (value 41.27 for quercetin and 142.58 for taxifolin) than the well-known reference, ascorbic acid (value 65.36 for quercetin and 58.43 for taxifolin) but less potency than the standard gallic acid. The discussion of SAR of the antioxidant potential revealed that the type of natural product is crucial for the activity and the substitution pattern on the flavonoid skeleton modulate the antioxidant profile. Our findings show that I. viscosa leaves may be a natural source of antioxidants and once again the role of flavonoids health benefits is more strongly endorsed.

Plicosepalus acacia Extract and Its Major Constituents, Methyl Gallate and Quercetin, Potentiate Therapeutic Angiogenesis in Diabetic Hind Limb Ischemia: HPTLC Quantification and LC-MS/MS Metabolic Profiling

Plicosepalus acacia (Fam. Loranthaceae) has been reported to possess hypoglycemic, antioxidant, antimicrobial, and anti-inflammatory effects. Liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) analysis revealed the presence of a high content of polyphenolic compounds that are attributed to the therapeutic effects of the crude extract. In addition, methyl gallate and quercetin were detected as major phytomedicinal agents at concentrations of 1.7% and 0.062 g%, respectively, using high-performance thin layer chromatography (HPTLC). The present study investigated the effect of the P. acacia extract and its isolated compounds, methyl gallate and quercetin, on hind limb ischemia induced in type 1 diabetic rats. Histopathological examination revealed that treatment with P. acacia extract, methyl gallate, and quercetin decreased degenerative changes and inflammation in the ischemic muscle. Further biochemical assessment of the hind limb tissue showed decreased oxidative stress, increased levels of nitric oxide and endothelial nitric oxide synthase (eNOS), and enhancement of the levels of heme oxygenase-1 (HO-1) and vascular endothelial growth factor (VEGF) in the groups treated with methyl gallate and quercetin. Expression levels of hypoxia inducible factor-1 alpha (HIF-1α), VEGF, fibroblast growth factor-2 (FGF-2), and miR-146a were upregulated in the muscle tissue of methyl gallate- and quercetin-treated groups along with downregulation of nuclear factor kappa B (NF-κB). In conclusion, P. acacia extract and its isolated compounds, methyl gallate and quercetin, mediated therapeutic angiogenesis in diabetic hind limb ischemia.