Flavonoids in Health and Disease

The Potential of Plant Extracts Used in Cosmetic Product Applications-Antioxidants Delivery and Mechanism of Actions

Natural ingredients have been used in skincare products for thousands of years. The current focus is on novel natural bioactivities that shield the skin from UV rays and free radicals, among other damaging elements, while enhancing skin health. Free radicals significantly contribute to skin damage and hasten ageing by interfering with defence and restorative processes. Plants contain natural chemicals that can scavenge free radicals and have antioxidant capabilities. Plant materials are becoming increasingly popular as natural antioxidants related to the expanding interest in plant chemistry. This review focuses on the significance of medicinal plants in skin health and ageing and their potential as a source of antioxidant substances such as vitamins, polyphenols, stilbenes, flavonoids, and methylxanthines.

Total synthesis/semi-synthesis of natural isopentenyl flavonoids with inhibitory activity on NLRP3 inflammasome

Inflammation is the body's defense response to stimuli. When the homeostatic balance is disturbed, disease may result. Flavonoids have clear anti-inflammatory effects and the isopentenyl group significantly enhances the pharmacological activity of flavonoids. Therefore, isopentenyl flavonoids have the potential to serve as lead compounds for the development of anti-inflammatory drugs. Throughout this research, eight natural compounds were synthesized, including 5,7-dihydroxy-4'-methoxy-8-prenylflavonoid (1), 4'-O-Methylatalantoflavone (2), Kushenol W (3) and Racemoflavone (5), which were totally synthesized for the first time. Additionally, three flavonols: Licoflavonol (6), 3,5,7,3',4'-pentahydroxy-6-prenylflavonol (7) and Macarangin (8), can be one-step synthesized by direct C-isopentenylation. In the process, an economical and efficient C-isopentenylation method was also simultaneously explored that could facilitate the efficient synthesis of natural products. These compounds were evaluated for their potential anti-inflammatory activities via the NLRP3 signaling pathway. Notably, Macarangin (8) manifested the most potent inhibitory effect. The SAR (Structure-Activity Relationships) also showed the introduction of the isopentenyl group was determined to enhance these effects, whereas simple flavonoid frameworks or cyclization of isopentenyl groups all diminished anti-inflammatory activity.

Designing plant flavonoids: harnessing transcriptional regulation and enzyme variation to enhance yield and diversity

Plant synthetic biology has emerged as a powerful and promising approach to enhance the production of value-added metabolites in plants. Flavonoids, a class of plant secondary metabolites, offer numerous health benefits and have attracted attention for their potential use in plant-based products. However, achieving high yields of specific flavonoids remains challenging due to the complex and diverse metabolic pathways involved in their biosynthesis. In recent years, synthetic biology approaches leveraging transcription factors and enzyme diversity have demonstrated promise in enhancing flavonoid yields and expanding their production repertoire. This review delves into the latest research progress in flavonoid metabolic engineering, encompassing the identification and manipulation of transcription factors and enzymes involved in flavonoid biosynthesis, as well as the deployment of synthetic biology tools for designing metabolic pathways. This review underscores the importance of employing carefully-selected transcription factors to boost plant flavonoid production and harnessing enzyme promiscuity to broaden flavonoid diversity or streamline the biosynthetic steps required for effective metabolic engineering. By harnessing the power of synthetic biology and a deeper understanding of flavonoid biosynthesis, future researchers can potentially transform the landscape of plant-based product development across the food and beverage, pharmaceutical, and cosmetic industries, ultimately benefiting consumers worldwide.

The Interaction between Feed Bioactive Compounds and Chicken Genome

Consumer demand for high quality and safe foods that will have a positive impact on their health has increased in recent years. Today, it is possible to meet those demands by combining the genetic potential of domestic animals and applying different feeding strategies. Nutrigenomics is one of the "omics" sciences that studies the interaction between nutrients and the genome together with their influence on metabolic and physiological processes in the body. While nutrition of domestic animals is solely based on studying the influence of nutrients on animal health and production traits, nutrigenomics integrates the fields of nutrition, genomics, molecular genetics and bioinformatics. By understanding the molecular relationships between different forms and/or concentrations of nutrients in feed and genes, it is possible to answer the question of how small changes in the diet of farm animals can produce a quality product with positive effects on human health. The aim of this article is to describe how the manipulation of adding different nutrients in the feed affects the expression of different genes in chicken and consequently alters their phenotype.

Aging Injury Impairs Structural Properties and Cell Signaling in Human Red Blood Cells; Açaì Berry Is a Keystone

Red blood cell (RBC) deformability is the ability of cells to modulate their shape to ensure transit through narrow capillaries of the microcirculation. A loss of deformability can occur in several pathological conditions, during natural RBC aging through an increase in membrane protein phosphorylation, and/or through the structural rearrangements of cytoskeletal proteins due to oxidative conditions, with a key role played by band 3. Due to the close relationship between aging and oxidative stress, flavonoid-rich foods are good candidates to counteract age-related alterations. This study aims to verify the beneficial role of Açaì extract in a d-Galactose (d-Gal)-induced model of aging in human RBCs. To this end, band 3 phosphorylation and structural rearrangements in membrane cytoskeleton-associated proteins, namely spectrin, ankyrin, and/or protein 4.1, are analyzed in RBCs treated with 100 mM d-Gal for 24 h, with or without pre-incubation with 10 μg/mL Açaì extract for 1 h. Furthermore, RBC deformability is also measured. Tyrosine phosphorylation of band 3, membrane cytoskeleton-associated proteins, and RBC deformability (elongation index) are analyzed using western blotting analysis, FACScan flow cytometry, and ektacytometry, respectively. The present data show that: (i) Açaì berry extract restores the increase in band 3 tyrosine phosphorylation and Syk kinase levels after exposure to 100 mM d-Gal treatment; and (ii) Açaì berry extract partially restores alterations in the distribution of spectrin, ankyrin, and protein 4.1. Interestingly, the significant decrease in membrane RBC deformability associated with d-Gal treatment is alleviated by pre-treatment with Açaì extract. These findings further contribute to clarify mechanisms of natural aging in human RBCs, and propose flavonoid substances as potential natural antioxidants for the treatment and/or prevention of oxidative-stress-related disease risk.

Simultaneous quantification of 3',4'-dimethoxy flavonol-3-O-glucoside and its major metabolite in human plasma by LC-MS/MS and its application to a clinical pharmacokinetic study

Hyperlipidemia is a disease characterized by abnormal blood lipid levels and is the leading risk factor for cardiovascular disease. 3',4'-Dimethoxy flavonol-3-O-glucoside (abbreviated DF3G) is a new lipid-lowering drug created as a flavonoid structural analog. The principal metabolite of DF3G in human plasma is the aglycone glucuronide conjugate M2. The purpose of this study is to use liquid chromatography-tandem mass spectrometry to develop and validate a quantitative analysis method for DF3G and its metabolite M2 in human plasma, and to use the method to investigate the pharmacokinetics of DF3G and M2 in a clinical trial. This method employed DF3G-d₆ as the internal standard, and plasma samples were processed by protein precipitation. Isocratic separation could accurately differentiate DF3G, M2, and DF3G-d₆ from endogenous components in the matrix or other components in the samples, and endogenous components in the matrix had little impact on ionization efficiency. Positive electrospray ionization with multiple reaction monitoring (MRM) transitions of m/z 461.2 → 299.0 for DF3G, m/z 475.1 → 299.1 for M2 and m/z 467.1 → 305.1 for DF3G-d₆ was used for quantification. The DF3G and M2 linear range for plasma were in the range of 4.00/4.00 ng/mL to 4000/4000 ng/mL. Both the analytes and the internal standard were stable regardless of whether they were in solution or plasma samples. The accuracy of the average concentration of the quality control samples was within 15% of the theoretical value, and the RSD was less than 15%. The method is rapid, accurate, straightforward, and precise. It is appropriate for the determination of DF3G and M2 concentrations in human plasma and has been successfully applied to determine the pharmacokinetic analysis in phase I clinical trials.

The role and mechanism of flavonoid herbal natural products in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease of the intestine that presents clinically with abdominal pain, mucopurulent stools, and posterior urgency. The lesions of UC are mainly concentrated in the rectal and colonic mucosa and submucosa. For patients with mild to moderate UC, the best pharmacological treatment includes glucocorticoids, immunosuppressants, antibiotics, and biologics, but the long-term application can have serious toxic side effects. Currently, nearly 40% of UC patients are treated with herbal natural products in combination with traditional medications to reduce the incidence of toxic side effects. Flavonoid herbal natural products are the most widely distributed polyphenols in plants and fruits, which have certain antioxidant and anti-inflammatory activities. Flavonoid herbal natural products have achieved remarkable efficacy in the treatment of UC. The pharmacological mechanisms are related to anti-inflammation, promotion of mucosal healing, maintenance of intestinal immune homeostasis, and regulation of intestinal flora. In this paper, we summarize the flavonoid components of anti-ulcerative colitis and their mechanisms reported in the past 10 years, to provide a basis for rational clinical use and the development of new anti-ulcerative colitis drugs.

A bioactive component of Portulaca Oleracea L., HM-chromanone, improves palmitate-induced insulin resistance by inhibiting mTOR/S6K1 through activation of the AMPK pathway in L6 skeletal muscle cells

Increased free fatty acid levels in the blood are common in obesity and cause insulin resistance associated with type 2 diabetes in the muscles. Previous studies have confirmed the antidiabetic and anti-obesity potential of (E)-5-hydroxy-7-methoxy-3-(2-hydroxybenzyl)-4-chromanone (HM-chromanone). However, it is unknown how HM-chromanone alleviates obesity-related insulin resistance in L6 skeletal muscle cells. Palmitate induced insulin resistance and reduced glucose uptake, whereas HM-chromanone significantly increased glucose uptake. In palmitate-treated L6 skeletal muscle cells, HM-chromanone stimulated liver kinase B1 (LKB1) and 5'-adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. The AMPK inhibitor compound C, and the LKB1 inhibitor radicicol blocked the effects of HM-chromanone. Furthermore, HM-chromanone significantly inhibited mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase 1 (S6K1) activation, but there was no change in protein kinase C θ (PKC θ) expression. When pAMPK was inhibited with compound C, the effect of HM-chromanone on the inhibition of mTOR and S6K1 was significantly diminished. This indicates that HM-chromanone inhibits mTOR and S6K1 activation through pAMPK activation. Inhibition of mTOR and S6K1 by HM-chromanone significantly reduced IRS-1Ser307 and IRS-1Ser632 phosphorylation, leading to insulin resistance. This resulted in an increase in PM-GLUT4 (glucose transporter 4) expression, thereby stimulating glucose uptake in insulin-resistant muscle cells. HM-chromanone can improve palmitate-induced insulin resistance by inhibiting mTOR and S6K1 through activation of the AMPK pathway in L6 skeletal muscle cells. These results show the therapeutic potential of HM-chromanone for improving insulin resistance in type 2 diabetes.

Antioxidant Activity of Quercetin in a H2O2-Induced Oxidative Stress Model in Red Blood Cells: Functional Role of Band 3 Protein

During their lifespan, red blood cells (RBCs) are exposed to a large number of stressors and are therefore considered as a suitable model to investigate cell response to oxidative stress (OS). This study was conducted to evaluate the potential beneficial effects of the natural antioxidant quercetin (Q) on an OS model represented by human RBCs treated with H₂O₂. Markers of OS, including % hemolysis, reactive oxygen species (ROS) production, thiobarbituric acid reactive substances (TBARS) levels, oxidation of protein sulfhydryl groups, CD47 and B3p expression, methemoglobin formation (% MetHb), as well as the anion exchange capability through Band 3 protein (B3p) have been analyzed in RBCs treated for 1 h with 20 mM H₂O₂ with or without pre-treatment for 1 h with 10 μM Q, or in RBCs pre-treated with 20 mM H₂O₂ and then exposed to 10 µM Q. The results show that pre-treatment with Q is more effective than post-treatment to counteract OS in RBCs. In particular, pre-exposure to Q avoided morphological alterations (formation of acanthocytes), prevented H₂O₂-induced OS damage, and restored the abnormal distribution of B3p and CD47 expression. Moreover, H₂O₂ exposure was associated with a decreased rate constant of SO₄²⁻ uptake via B3p, as well as an increased MetHb formation. Both alterations have been attenuated by pre-treatment with 10 μM Q. These results contribute (1) to elucidate OS-related events in human RBCs, (2) propose Q as natural antioxidant to counteract OS-related alterations, and (3) identify B3p as a possible target for the treatment and prevention of OS-related disease conditions or aging-related complications impacting on RBCs physiology.

Açaì (Euterpe oleracea) Extract Protects Human Erythrocytes from Age-Related Oxidative Stress

Aging is a process characterised by a general decline in physiological functions. The high bioavailability of reactive oxygen species (ROS) plays an important role in the aging rate. Due to the close relationship between aging and oxidative stress (OS), functional foods rich in flavonoids are excellent candidates to counteract age-related changes. This study aimed to verify the protective role of Açaì extract in a d-Galactose (d-Gal)-induced model of aging in human erythrocytes. Markers of OS, including ROS production, thiobarbituric acid reactive substances (TBARS) levels, oxidation of protein sulfhydryl groups, as well as the anion exchange capability through Band 3 protein (B3p) and glycated haemoglobin (A1c) have been analysed in erythrocytes treated with d-Gal for 24 h, with or without pre-incubation for 1 h with 0.5–10 µg/mL Açaì extract. Our results show that the extract avoided the formation of acanthocytes and leptocytes observed after exposure to 50 and 100 mM d-Gal, respectively, prevented d-Gal-induced OS damage, and restored alterations in the distribution of B3p and CD47 proteins. Interestingly, d-Gal exposure was associated with an acceleration of the rate constant of SO₄²⁻ uptake through B3p, as well as A1c formation. Both alterations have been attenuated by pre-treatment with the Açaì extract. These findings contribute to clarify the aging mechanisms in human erythrocytes and propose functional foods rich in flavonoids as natural antioxidants for the treatment and prevention of OS-related disease conditions.

In Vitro and In Silico Antioxidant Efficiency of Bio-Potent Secondary Metabolites From Different Taxa of Black Seed-Producing Plants and Their Derived Mycoendophytes

Oxidative stress is involved in the pathophysiology of multiple health complications, and it has become a major focus in targeted research fields. As known, black seeds are rich sources of bio-active compounds and widely used to promote human health due to their excellent medicinal and pharmaceutical properties. The present study investigated the antioxidant potency of various black seeds from plants and their derived mycoendophytes, and determined the total phenolic and flavonoid contents in different extracts, followed by characterization of major constituents by HPLC analysis. Finally, in silico docking determined their binding affinities to target myeloperoxidase enzymes. Ten dominant mycoendophytes were isolated from different black seed plants. Three isolates were then selected based on high antiradical potency and further identified by ITS ribosomal gene sequencing. Those isolated were Aspergillus niger TU 62, Chaetomium madrasense AUMC14830, and Rhizopus oryzae AUMC14823. Nigella sativa seeds and their corresponding endophyte A. niger had the highest content of phenolics in their n-butanol extracts (28.50 and 24.43 mg/g), flavonoids (15.02 and 11.45 mg/g), and antioxidant activities (90.48 and 81.48%), respectively, followed by Dodonaea viscosa and Portulaca oleracea along with their mycoendophytic R. oryzae and C. madrasense. Significant positive correlations were found between total phenolics, flavonoids, and the antioxidant activities of different tested extracts. The n-butanol extracts of both black seeds and their derived mycoendophytes showed reasonable IC50 values (0.81–1.44 mg/ml) compared to the control with significant correlations among their phytochemical contents. Overall, seventeen standard phenolics and flavonoids were used, and the compounds were detected in different degrees of existence and concentration in the examined extracts through HPLC analysis. Moreover, the investigation of the molecular simulation results of detected compounds against the myeloperoxidase enzyme revealed that, as a targeted antioxidant, rutin possessed a high affinity (−15.3184 kcal/mol) as an inhibitor. Taken together, the black seeds and their derived mycoendophytes are promising bio-prospects for the broad industrial sector of antioxidants with several valuable potential pharmaceutical and nutritional applications.

Balancing Damage via Non-Photochemical Quenching, Phenolic Compounds and Photorespiration in Ulva prolifera Induced by Low-Dose and Short-Term UV-B Radiation

The Yellow Sea green tide (YSGT) is the world’s largest transregional macroalgal blooms, and the causative species Ulva prolifera (U. prolifera) suffers from ultraviolet-b radiation (UVBR) during the floating migration process. Previous study confirmed that U. prolifera displayed a wide variety of physiological responses characterized as acclimation to UVBR, while the response mechanisms against low-dose and short-term radiation (LDSTR) are not clear. A study with photosynthetically active radiation (PAR) and UVBR was designed: normal light (NL: 72 μmol photons m⁻² s⁻¹), NL+0.3 (UVBR: 0.3 W·m⁻²), and NL+1.6 (UVBR: 1.6 W·m⁻²). The results showed that high-dose UVBR inhibited photosynthesis in thalli, especially under long-term exposure, while a variety of physiological responses were observed under LDSTR. The inhibition of photosynthesis appeared to be ameliorated by the algae under LDSTR. Further analysis showed that U. prolifera achieved balancing damage by means of non-photochemical quenching (NPQ), accumulation of phenolic compounds coupled with the ASA-GSH cycle involved in the antioxidant process and enhanced photorespiratory metabolism under LDSTR. This study provides new insights into the balancing damage mechanisms of U. prolifera under LDSTR, enabling the thalli to adapt to the light conditions during the long duration and distance involved in floating migration.

Evaluation of Enzyme Inhibitory Activity of Flavonoids by Polydopamine-Modified Hollow Fiber-Immobilized Xanthine Oxidase

In this study, a polydopamine (PDA)-modified hollow fiber-immobilized xanthine oxidase (XOD) was prepared for screening potential XOD inhibitors from flavonoids. Several parameters for the preparation of PDA-modified hollow fiber-immobilized XOD, including the dopamine concentration, modification time, XOD concentration and immobilization time, were optimized. The results show that the optimal conditions for immobilized XOD activity were a dopamine concentration of 2.0 mg/mL in 10.0 mM Tris-HCl buffer (pH 8.5), a modification time of 3.0 h, an XOD concentration of 1000 μg/mL in 10.0 mM phosphate buffer (pH 7.5) and an immobilization time of 3.0 h. Subsequently, the enzymatic reaction conditions such as the pH value and temperature were investigated, and the enzyme kinetics and inhibition parameters were determined. The results indicate that the optimal pH value (7.5) and temperature (37 °C) of the PDA-modified hollow fiber-immobilized XOD were consistent with the free enzyme. Moreover, the PDA-modified hollow fiber-immobilized XOD could still maintain above 50% of its initial immobilized enzyme activity after seven consecutive cycles. The Michaelis–Menten constant (K_m) and the half-maximal inhibitory concentration (IC₅₀) of allopurinol on the immobilized XOD were determined as 0.25 mM and 23.2 μM, respectively. Furthermore, the PDA-modified hollow fiber-immobilized XOD was successfully applied to evaluate the inhibitory activity of eight flavonoids. Quercetin, apigenin, puerarin and epigallocatechin showed a good inhibition effect, and their percentages of inhibition were (79.86 ± 3.50)%, (80.98 ± 0.64)%, (61.15 ± 6.26)% and (54.92 ± 0.41)%, respectively. Finally, molecular docking analysis further verified that these four active compounds could bind to the amino acid residues in the XOD active site. In summary, the PDA-modified hollow fiber-immobilized XOD is an efficient method for the primary screening of XOD inhibitors from natural products.

Lensoside Aβ as an Adjuvant to the Anti-Glioma Potential of Sorafenib

Simple Summary

Flavonoids are plant polyphenolic secondary metabolites, commonly consumed in the human diet. Lensoside Aβ is a quercetin glycoside isolated from the aerial parts of lentil (Lens culinaris) organs. The activity of this secondary metabolite, especially in terms of its anticancer potential, has been poorly studied. Currently, there are no published data about the effect of this flavonoid on gliomas, which are so-far incurable, aggressive neoplasms of the central nervous system with a highly infiltrative character. In this study, we found that lensoside Aβ itself exhibits poor anti-glioma properties but exerts a strongly potentiated effect in combination with sorafenib (inhibitor of Raf kinase) on apoptosis induction in cancer cells. Our results have shown that sorafenib with lensoside Aβ seems to be a promising combination that might be useful in glioma therapy. Additionally, the former observation, pointing to the key role of flavonoids as adjuvants in chemotherapy, is confirmed.

Abstract

Aim: The anti-glioma effect of lensoside Aβ alone and in combination with sorafenib (pro-survival Raf kinase inhibitor) was evaluated for the first time in terms of programmed cell death induction in anaplastic astrocytoma and glioblastoma multiforme cell lines as an experimental model. Apoptosis, autophagy, and necrosis were identified microscopically (fluorescence and scanning microscopes) and confirmed by flow cytometry (mitochondrial membrane potential MMP and cell death). The expression of apoptotic (caspase 3) and autophagic markers (beclin 1) as well as Raf kinase were estimated by immunoblotting. The FTIR method was used to determine the interaction of the studied drugs with lipid and protein groups within cells, while the modes of drug action within the cells were assessed with the FLIM technique. Results: Lensoside Aβ itself does not exhibit anti-glioma activity but significantly enhances the anti-cancer potential of sorafenib, initiating mainly apoptosis of up to 90% of cells. It was correlated with an increased level of active caspase 3, a reduced MMP value, and a lower level of Raf kinase. The interaction with membrane structures led to morphological changes typical of programmed death. Conclusions: Our results indicate that lensoside Aβ plays an important role as an adjuvant in chemotherapy with sorafenib and may be a potential candidate in anti-glioma combination therapy.

Onion Peel: Turning a Food Waste into a Resource

Food waste is a serious problem for food processing industries, especially when it represents a loss of a valuable source of nutrients and phytochemicals. Increasing consumer demand for processed food poses the problem of minimizing waste by conversion into useful products. In this regard, onion (Allium cepa) waste consisting mainly of onion skin is rich in bioactive phenolic compounds. Here, we characterized the flavonoid profiles and biological activities of onion skin wastes of two traditional varieties with protected geographical indication (PGI), the red “Rossa di Tropea” and the coppery “Ramata di Montoro”, typically cultivated in a niche area in southern Italy. The phytochemical profiles of exhaustive extracts, characterized by ultra-high-performance liquid chromatography coupled with ultraviolet (UV) detection and high-resolution mass spectrometry, revealed that flavonols and anthocyanins were the characteristic metabolite classes of onion skins. Quercetin, quercetin glucosides and their dimer and trimer derivatives, and, among anthocyanins, cyanidin 3-glucoside, were the most abundant bioactive compounds. The potential of onion skins was evaluated by testing several biological activities: ABTS/oxygen radical absorbance capacity (ORAC) and in vitro alpha-glucosidase assays were performed to evaluate the antioxidant and anti-diabetic properties of the extracts and of their main compounds, respectively, and proliferative activity was evaluated by MTT assay on human fibroblasts. In the present study, by observing various biological properties of “Rossa di Tropea” and “Ramata di Montoro” onion-dried skins, we clearly indicated that this agricultural waste can provide bioactive molecules for multiple applications, from industrial to nutraceutical and cosmetical sectors.

Evaluation of xanthine oxidase inhibitory activity of flavonoids by an online capillary electrophoresis-based immobilized enzyme microreactor

Xanthine oxidase (XOD) is a key enzyme in the human body to produce uric acid, and its inhibitor can be used for the treatment of hyperuricemia and gout. In this study, an online CE-based XOD immobilized enzyme microreactor (IMER) was developed for the enzyme kinetics assays and inhibitor screening. After 30 consecutive runs, the XOD activity remained about 95.6% of the initial immobilized activity. The Michaelis-Menten constant (K_m ) of the immobilized XOD was determined as 0.39 mM using xanthine as substrate. The half-maximal inhibitory concentration and inhibition constant of the known inhibitor 4-aminopyrazolo[3,4-d]pyrimidine on XOD were determined as 11.9 and 5.2 μM, respectively. Then, the developed method was applied to evaluate the XOD inhibitory activity of 10 flavonoids, which indicated that dihydroquercetin, quercetin, biochanin A, and epicatechin had significant inhibitory effect on XOD. In addition, molecular docking results verified that the binding energy of the flavonoids with enzyme were in line with their inhibitory activity determined by XOD-IMER. Therefore, the developed XOD-IMER is a potential tool for the primary screening of XOD inhibitors from natural products.