Quercetin Metabolites Up-Regulate the Antioxidant Response in Osteoblasts Isolated From Fetal Rat Calvaria

Therapeutic Potential of Quercetin as an Antioxidant for Bone-Muscle-Tendon Regeneration and Aging

Quercetin (QC), a naturally occurring bioflavonoid found in various fruits and vegetables, possesses many potential health benefits, primarily attributed to its robust antioxidant properties. The generation of oxidative stress in bone cells is a key modulator of their physiological behavior. Moreover, oxidative stress status influences the pathophysiology of mineralized tissues. Increasing scientific evidence demonstrates that manipulating the redox balance in bone cells might be an effective technique for developing bone disease therapies. The QC antioxidant abilities in skeletal muscle significantly enhance muscle regeneration and reduce muscle atrophy. In addition, QC has been shown to have protective effects against oxidative stress, inflammation, apoptosis, and matrix degradation in tendons, helping to maintain the structural integrity and functionality of tendons. Thus, the antioxidant properties of QC might be crucial for addressing age-related musculoskeletal disorders like osteoporosis, sarcopenia, and tendon-related inflammatory conditions. Understanding how QC influences redox signaling pathways involved in musculoskeletal disorders, including their effect on bone, muscle, and tendon differentiation, might provide insights into the diverse advantages of QC in promoting tissue regeneration and preventing cellular damage. Therefore, this study reviewed the intricate relationship among oxidative stress, inflammation, and tissue repair, affected by the antioxidative abilities of QC, in age-related musculoskeletal tissues to improve the overall health of bones, muscles, and tendons of the skeletal system. Also, reviewing the ongoing clinical trials of QC for musculoskeletal systems is encouraging. Given the positive effect of QC on musculoskeletal health, further scientific investigations and controlled human intervention studies are necessary to explore the therapeutic potential to its optimum strength.

New perspectives on the therapeutic potential of quercetin in non-communicable diseases: Targeting Nrf2 to counteract oxidative stress and inflammation

Non-communicable diseases (NCDs), including cardiovascular diseases, cancer, metabolic diseases, and skeletal diseases, pose significant challenges to public health worldwide. The complex pathogenesis of these diseases is closely linked to oxidative stress and inflammatory damage. Nuclear factor erythroid 2-related factor 2 (Nrf2), a critical transcription factor, plays an important role in regulating antioxidant and anti-inflammatory responses to protect the cells from oxidative damage and inflammation-mediated injury. Therefore, Nrf2-targeting therapies hold promise for preventing and treating NCDs. Quercetin (Que) is a widely available flavonoid that has significant antioxidant and anti-inflammatory properties. It modulates the Nrf2 signaling pathway to ameliorate oxidative stress and inflammation. Que modulates mitochondrial function, apoptosis, autophagy, and cell damage biomarkers to regulate oxidative stress and inflammation, highlighting its efficacy as a therapeutic agent against NCDs. Here, we discussed, for the first time, the close association between NCD pathogenesis and the Nrf2 signaling pathway, involved in neurodegenerative diseases (NDDs), cardiovascular disease, cancers, organ damage, and bone damage. Furthermore, we reviewed the availability, pharmacokinetics, pharmaceutics, and therapeutic applications of Que in treating NCDs. In addition, we focused on the challenges and prospects for its clinical use. Que represents a promising candidate for the treatment of NCDs due to its Nrf2-targeting properties.

Pharmacological and mechanistic aspects of quercetin in osteoporosis

Osteoporosis (OP) is a bone disease associated with increasing age. Currently, the most common medications used to treat OP are anabolic agents, anti-resorptive agents, and medications with other mechanisms of action. However, many of these medications have unfavorable adverse effects or are not intended for long-term use, potentially exerting a severe negative impact on a patient's life and career and placing a heavy burden on families and society. There is an urgent need to find new drugs that can replace these and have fewer adverse effects. Quercetin (Que) is a common flavonol in nature. Numerous studies have examined the therapeutic applications of Que. However, a comprehensive review of the anti-osteoporotic effects of Que has not yet been conducted. This review aimed to describe the recent studies on the anti-osteoporotic effects of Que, including its biological, pharmacological, pharmacokinetic, and toxicological properties. The outcomes demonstrated that Que could enhance OP by increasing osteoblast differentiation and activity and reducing osteoclast differentiation and activity via the pathways of Wnt/β-catenin, BMP/SMAD/RUNX2, OPG/RANKL/RANK, ERK/JNK, oxidative stress, apoptosis, and transcription factors. Thus, Que is a promising novel drug for the treatment of OP.

Bioactivity of the Ethanol Extract of Clove (Syzygium aromaticum) as Antitoxin

Toxic compounds can induce the formation of free radicals (reactive oxygen species (ROS)) which can trigger damage and decrease cell viability. Clove (Syzygium aromaticum) contains phenolic compounds that are useful as antioxidants which can reduce ROS toxicity. However, little is known about the antitoxin activity of clove extract. Therefore, this study is aimed at determining the effect of ethanolic clove extract as an antitoxin agent against malachite green (MG) mutagen using the yeast Saccharomyces cerevisiae as a model. The methods used to analyze the ability of ethanolic clove extract as antitoxin were decolorization assay and cell viability test towards MG. The phenol contents of leaf and bud extract were 441.28 and 394.73 mg GAE g-1 extract, respectively. Clove leaf extract has strong antioxidant activity in vitro (IC50 9.29 ppm for 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 29.57 for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)). Liquid chromatography quadrupole-mass spectrometry (LC-MS/MS) analysis showed the presence of 4-O-caffeoylquinic acid and several other bioactive compounds, in which these compounds had bioactivity against toxic compound. The addition of extract reduced the ability of S. cerevisiae to decolorize malachite green but increased cell viability. Based on the data, clove leaf extract shows the potential antitoxin activity. This research should facilitate a preliminary study to investigate the antitoxin agent derived from cloves leaf extract. Further research to analyze the antitoxin mechanism of this extract in yeast model is interesting to do to provide a comprehensive insight into the potential antitoxin agents of clove leaf extract.

Research progress in physiological effects of resistant substances of Urtica dioica L. on animal performance and feed conversion

Several members of family Urticaceae are mainly found in the temperate and subtropical zones of the Northern Hemisphere and are important medicinal plants. Among them, Urtica dioica L. (Urticaceae) is an annual or perennial herb that has been used for feeding and medicinal purposes since long time and is the most exploited species of Urticaceae. Recently, it has received attention to be used as animal feed, as its fresh leaves fed to animals in moderate, dried, and other forms. This review details the advantages of U. dioica as an alternative feed in terms of germplasm specificity, nutritional composition, and feed application status. Its roots, stems, leaves, and seeds are rich in active ingredients. It has also been found to have anticancer effects through antioxidant action and promotion of apoptosis of cancer cells. In shady conditions, U. dioica is highly adaptable while under stressful conditions of drought; it also reduces light absorption and ensures carbon assimilation through light energy conversion efficiency. Therefore, it can be added to animal diets as a suitable feed to reduce costs and improve economic efficiency. This paper investigates the feasibility of using U. dioica as a feed and systematically presents the progress of research and exploitation of U. dioica.

Research on the Mechanism of Liuwei Dihuang Decoction for Osteoporosis Based on Systematic Biological Strategies

Background

Osteoporosis is an important health problem worldwide. Liuwei Dihuang Decoction (LDD) and its main ingredients may have a good clinical effect on osteoporosis. Meanwhile, its mechanism for treating osteoporosis needs to be further revealed in order to provide a basis for future drug development.

Methods

A systematic biological methodology was utilized to construct and analyze the LDD-osteoporosis network. After that, the human transcription data of LDD intervention in patients with osteoporosis and protein arrays data of LDD intervention in osteoporosis rats were collected. The human transcription data analysis, protein arrays data analysis, and molecular docking were performed to validate the findings of the prediction network (LDD-osteoporosis PPI network). Finally, animal experiments were conducted to verify the prediction results of systematic pharmacology.

Results

(1) LDD-osteoporosis PPI network shows the potential compounds, potential targets (such as ALB, IGF1, SRC, and ESR1), clusters, biological processes (such as positive regulation of calmodulin 1-monooxygenase activity, estrogen metabolism, and endothelial cell proliferation), and signaling and Reactome pathways (such as JAK-STAT signaling pathway, osteoclast differentiation, and degradation of the extracellular matrix) of LDD intervention in osteoporosis. (2) Human transcriptomics data and protein arrays data validated the findings of the LDD-osteoporosis PPI network. (3) The animal experiments showed that LDD can improve bone mineral density (BMD), increase serum estradiol (E2) and alkaline phosphatase (ALP) levels, and upregulate Wnt3a and β-catenin mRNA expression (P < 0.05). (4) Molecular docking results showed that alisol A, dioscin, loganin, oleanolic acid, pachymic acid, and ursolic acid may stably bind to JAK2, ESR1, and CTNNB1.

Conclusion

LDD may have a therapeutic effect on osteoporosis through regulating the targets (such as ALB, IGF1, SRC, and ESR1), biological processes (such as positive regulation of calmodulin 1-monooxygenase activity, estrogen metabolism, and endothelial cell proliferation), and pathways (such as JAK-STAT signaling pathway, osteoclast differentiation, and degradation of the extracellular matrix) found in this research.

Comparison of metabolism and biological properties among positional isomers of quercetin glucuronide in LPS- and RANKL-challenged RAW264.7 cells

The major quercetin metabolite, quercetin-3-glucuronide, exerts various biological activities, including anti-inflammatory effects. This study aimed to evaluate the metabolic profiles and biological properties of the positional isomers of quercetin monoglucuronides (Q3G, Q7G, Q3'G, and Q4'G) in activated macrophages. In addition to quercetin aglycone, Q7G was more cytotoxic than the other quercetin monoglucuronides (QGs), which corresponded to its lower stability under neutral pH conditions. Q3G was most effective in inhibiting both LPS-dependent induction of IL-6 and RANKL-dependent activation of tartrate-resistant acid phosphatase; however, Q3'G and Q4'G may also help exert biological activities without potential cytotoxicity. The deconjugation efficacy to generate quercetin aglycone differed among QGs, with the highest efficacy in Q3G. These results suggest that the chemical or biological properties and metabolic profiles may depend on the stability of QGs to generate quercetin aglycone using β-glucuronidase.

Traditional Chinese Medicine Compound-Loaded Materials in Bone Regeneration

Bone is a dynamic organ that has the ability to repair minor injuries via regeneration. However, large bone defects with limited regeneration are debilitating conditions in patients and cause a substantial clinical burden. Bone tissue engineering (BTE) is an alternative method that mainly involves three factors: scaffolds, biologically active factors, and cells with osteogenic potential. However, active factors such as bone morphogenetic protein-2 (BMP-2) are costly and show an unstable release. Previous studies have shown that compounds of traditional Chinese medicines (TCMs) can effectively promote regeneration of bone defects when administered locally and systemically. However, due to the low bioavailability of these compounds, many recent studies have combined TCM compounds with materials to enhance drug bioavailability and bone regeneration. Hence, the article comprehensively reviewed the local application of TCM compounds to the materials in the bone regeneration in vitro and in vivo. The compounds included icariin, naringin, quercetin, curcumin, berberine, resveratrol, ginsenosides, and salvianolic acids. These findings will contribute to the potential use of TCM compound-loaded materials in BTE.

Revisiting the Oxidation of Flavonoids: Loss, Conservation or Enhancement of Their Antioxidant Properties

Flavonoids display a broad range of health-promoting bioactivities. Among these, their capacity to act as antioxidants has remained most prominent. The canonical reactive oxygen species (ROS)-scavenging mode of the antioxidant action of flavonoids relies on the high susceptibility of their phenolic moieties to undergo oxidation. As a consequence, upon reaction with ROS, the antioxidant capacity of flavonoids is severely compromised. Other phenol-compromising reactions, such as those involved in the biotransformation of flavonoids, can also markedly affect their antioxidant properties. In recent years, however, increasing evidence has indicated that, at least for some flavonoids, the oxidation of such residues can in fact markedly enhance their original antioxidant properties. In such apparent paradoxical cases, the antioxidant activity arises from the pro-oxidant and/or electrophilic character of some of their oxidation-derived metabolites and is exerted by activating the Nrf2–Keap1 pathway, which upregulates the cell’s endogenous antioxidant capacity, and/or, by preventing the activation of the pro-oxidant and pro-inflammatory NF-κB pathway. This review focuses on the effects that the oxidative and/or non-oxidative modification of the phenolic groups of flavonoids may have on the ability of the resulting metabolites to promote direct and/or indirect antioxidant actions. Considering the case of a metabolite resulting from the oxidation of quercetin, we offer a comprehensive description of the evidence that increasingly supports the concept that, in the case of certain flavonoids, the oxidation of phenolics emerges as a mechanism that markedly amplifies their original antioxidant properties. An overlooked topic of great phytomedicine potential is thus unraveled.

Flavonoids: Classification, Function, and Molecular Mechanisms Involved in Bone Remodelling

Flavonoids are polyphenolic compounds spotted in various fruits, vegetables, barks, tea plants, and stems and many more natural commodities. They have a multitude of applications through their anti-inflammatory, anti-oxidative, anti-carcinogenic properties, along with the ability to assist in the stimulation of bone formation. Bone, a rigid connective body tissue made up of cells embedded in a mineralised matrix is maintained by an assemblage of pathways assisting osteoblastogenesis and osteoclastogenesis. These have a significant impact on a plethora of bone diseases. The homeostasis between osteoblast and osteoclast formation decides the integrity and structure of the bone. The flavonoids discussed here are quercetin, kaempferol, icariin, myricetin, naringin, daidzein, luteolin, genistein, hesperidin, apigenin and several other flavonoids. The effects these flavonoids have on the mitogen activated protein kinase (MAPK), nuclear factor kappa β (NF-kβ), Wnt/β-catenin and bone morphogenetic protein 2/SMAD (BMP2/SMAD) signalling pathways, and apoptotic pathways lead to impacts on bone remodelling. In addition, these polyphenols regulate angiogenesis, decrease the levels of inflammatory cytokines and play a crucial role in scavenging reactive oxygen species (ROS). Considering these important effects of flavonoids, they may be regarded as a promising agent in treating bone-related ailments in the future.

Kaempferide enhances antioxidant capacity to promote osteogenesis through FoxO1/β-catenin signaling pathway

BACKGROUND

Forkhead box O1 (FoxO1)/β-catenin signaling pathway is a main oxidative defense pathway, which plays essential roles in the regulation of osteoporosis (OP). The natural products possess quality therapeutic effects and few side effects. It is used as a novel strategy in the treatment of OP. However, there is no systematic study in the natural antioxidant drug based on the FoxO1/β-catenin signaling pathway. This paper aims to discover pro-osteogenesis natural antioxidants for the prevention and treatment of OP.

METHODS

Systems pharmacology; combined with reverse drug targeting, systems-ADME process, network analysis and molecular docking, was used to screen natural antioxidants based on the FoxO1/β-catenin signaling pathway. Then in vitro experiments were performed to evaluate the osteogenesis effects of screened natural antioxidants.

RESULTS

Kaempferide was screened as the most potential antioxidant to improve osteogenesis by the regulation of the FoxO1/β-catenin signaling pathway. In vitro experiments showed that kaempferide significantly increased the expression of antioxidant genes and promoted osteogenic differentiation. Furthermore, kaempferide also improved the osteogenic differentiation inhibited by H2O2 through the enhancement of antioxidant capacity. Notably, kaempferide promoted cell antioxidant capacity by the increased nuclear translocation of FoxO1 and β-catenin.

CONCLUSIONS

These findings suggest that kaempferide is the natural antioxidant to promote osteogenesis effectively through the FoxO1/β-catenin signaling pathway. Natural antioxidant therapy maybe a promising strategy for the prevention and treatment of OP.

Quercetin Decreased Alveolar Bone Loss and Apoptosis in Experimentally Induced Periodontitis Model in Wistar Rats

BACKGROUND

Quercetin is a flavonoid which has potent anti-inflammatory, antibacterial, and antioxidant effect. Purpose of this study was to evaluate effects of quercetin on alveolar bone loss and histopathological changes in ligature-induced periodontitis in rats.

METHODS

Wistar rats were divided into four experimental groups: non-ligated control (C, n=8) group; periodontitis (P, n=8) group; ligature and low dose quercetin group (75 mg/kg/day quercetin, Q75 group, n=8); ligature and high dose quercetin group (150 mg/kg/day quercetin, Q150 group, n=8). Silk ligatures were placed at gingival margin of lower first molars of mandibular right quadrant. Study duration was 15 days, and animals were sacrificed end of this period. Changes in alveolar bone levels were clinically measured and tissues were immunohistochemically examined, matrix metalloproteinase 8 (MMP 8), inducible nitric oxide synthase (iNOS), tissue inhibitor of metalloproteinase 1 (TIMP 1), Cysteine-aspartic proteases 3 (Caspase 3), and tartrate-resistant acid phosphatase (TRAP) positive osteoclast cells, osteoblast, and neutrophil counts were also determined.

RESULTS AND DISCUSSION

Alveolar bone loss was highest in P group, and differences among P, Q75, and Q150 groups were significant. Both doses of quercetin decreased TRAP+ osteoclast cells and increased osteoblast cells. Inflammation in P group was also higher than those of C, Q75, and Q150 groups indicating anti-inflammatory effect of quercetin. iNOS, MMP-8, and caspase-3 levels were highest, and TIMP-1 expression was lowest in P group; differences were statistically significant.

CONCLUSION

Within limits of this study, it can be suggested that quercetin administration may reduce alveolar bone loss by increasing osteoblastic activity, decreasing osteoclastic activity, apoptosis, and inflammation in an experimental model of periodontitis.

Quercetin as an Agent for Protecting the Bone: A Review of the Current Evidence

Quercetin is a flavonoid abundantly found in fruits and vegetables. It possesses a wide spectrum of biological activities, thus suggesting a role in disease prevention and health promotion. The present review aimed to uncover the bone-sparing effects of quercetin and its mechanism of action. Animal studies have found that the action of quercetin on bone is largely protective, with a small number of studies reporting negative outcomes. Quercetin was shown to inhibit RANKL-mediated osteoclastogenesis, osteoblast apoptosis, oxidative stress and inflammatory response while promoting osteogenesis, angiogenesis, antioxidant expression, adipocyte apoptosis and osteoclast apoptosis. The possible underlying mechanisms involved are regulation of Wnt, NF-κB, Nrf2, SMAD-dependent, and intrinsic and extrinsic apoptotic pathways. On the other hand, quercetin was shown to exert complex and competing actions on the MAPK signalling pathway to orchestrate bone metabolism, resulting in both stimulatory and inhibitory effects on bone in parallel. The overall interaction is believed to result in a positive effect on bone. Considering the important contributions of quercetin in regulating bone homeostasis, it may be considered an economical and promising agent for improving bone health. The documented preclinical findings await further validation from human clinical trials.

Effect of Daily Ingestion of Quercetin-Rich Onion Powder for 12 Weeks on Visceral Fat: A Randomised, Double-Blind, Placebo-Controlled, Parallel-Group Study

Quercetin, which is frequently found in vegetables such as onion, is widely found to have biological activities such as visceral fat reduction. Therefore, we performed this randomised double-blind placebo-controlled parallel-group study and analysed the effects of daily intake of quercetin-rich onion on visceral fat for 12 weeks. Seventy healthy Japanese subjects whose body mass index (BMI) was ≥23 and <30 were recruited and randomly assigned to either the quercetin-rich onion group or placebo group. The subjects ingested 9 g of onion powder per day for 12 weeks. We conducted medical interviews, hematological and biological tests; measured body composition and vital signs; and analysed the Food Frequency Questionnaire weeks 0, 4, 8, and 12. Abdominal fat area was measured using computed tomography scanning at weeks 0 and 12. No significant differences in visceral fat area (VFA) were observed between the two groups. However, in subjects whose high-density lipoprotein cholesterol was lower, VFA was significantly lower in the quercetin-rich onion group. In addition, alanine aminotransferase was significantly lower in the quercetin-rich onion group than in the placebo group. Thus, the results suggest that quercetin-rich onion may be beneficial for preventing obesity and improving liver function.

Theoretical Study of the Antioxidant Activity of Quercetin Oxidation Products

It was recently shown that, when tested in cellular systems, quercetin oxidized products (Qox) have significantly better antioxidant activity than quercetin (Q) itself. The main Qox identified in the experiments are either 2,5,7,3',4'-pentahydroxy-3,4-flavandione (Fl) or its tautomer, 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (Bf). We have now performed a theoretical evaluation of different physicochemical properties using density functional theory (DFT) calculations on Q and its main Qox species. The most stable structures (for Q and Qox) were identified after a structural search on their potential energy surface. Since proton affinities (PAs) are much lower than the bond dissociation enthalpies (BDEs) of phenolic hydrogens, we consider that direct antioxidant activity in these species is mainly due to the sequential proton loss electron transfer (SPLET) mechanism. Moreover, our kinetic studies, according to transition state theory, show that Q is more favored by this mechanism. However, Qox have lower PAs than Q, suggesting that antioxidant activity by the SPLET mechanism should be a result of a balance between proclivity to transfer protons (which favors Qox) and the reaction kinetics of the conjugated base in the sequential electron transfer mechanism (which favors Q). Therefore, our results support the idea that Q is a better direct antioxidant than its oxidized derivatives due to its kinetically favored SPLET reactions. Moreover, our molecular docking calculations indicate a stabilizing interaction between either Q or Qox and the kelch-like ECH-associated protein-1 (Keap1), in the nuclear factor erythroid 2-related factor 2 (Nrf2)-binding site. This should favor the release of the Nrf2 factor, the master regulator of anti-oxidative responses, promoting the expression of the antioxidant responsive element (ARE)-dependent genes. Interestingly, the computed Keap1-metabolite interaction energy is most favored for the Bf compound, which in turn is the most stable oxidized tautomer, according to their computed energies. These results provide further support for the hypothesis that Qox species may be better indirect antioxidants than Q, reducing reactive oxygen species in animal cells by activating endogenous antioxidants.

Quercetin improve ischemia/reperfusion-induced cardiomyocyte apoptosis in vitro and in vivo study via SIRT1/PGC-1α signaling

AIM

To evaluate the effects of quercetin to improve ischemia/reperfusion-induced cardiomyocyte apoptosis in vitro and in vivo study.

METHODS

The cells were divided into five groups: model control (MC) group was ischemia/reperfusion (I/R) model group; DL group was treated with 25 mL/L quercetin based on MC group; DM group was treated with 50 ml/L quercetin based on MC group; DH group was treated with 100 mL/L quercetin based on MC group; Meto group was treated with metoprolol based on MC group. In the in vivo study, the rats were divided into five groups: MC group was I/R model group; DL group was treated with 25 mg/kg quercetin; DM group was treated with 50 mg/kg quercetin; DM group was treated with 100 mg/kg quercetin; Meto group was treated with Meto as positive drug.

RESULTS

The cell apoptosis rates of quercetin treated groups (DL, DM, and DH groups) were significantly suppressed compared with the MC group. The silent information regulatory factor 1 (SIRT1), peroxisome proliferators-activated receptor-γ coactivator-1α (PGC-1α), and Bcl-2 proteins expression of quercetin treated were significantly upregulation compared with MC group (P < 0.05, respectively), and Bax protein expression of quercetin treated group was significantly downregulation compared with MC group ( P < 0.05, respectively). In the vivo study, the myocardial pathological morphology of quercetin treated groups was improved. The cell apoptosis number of quercetin treated group were significantly suppressed compared with MC group by terminal deoxynucleotidyl transferase dUTP nick end labeling assay ( P < 0.05, respectively). SIRT1, PGC-1a, Bcl-2, and Bax proteins expressions of quercetin treated groups were significant differences compared with MC group in myocardial tissue ( P < 0.05, respectively).

CONCLUSION

Quercetin had improved the myocardial ischemia/reperfusion-induced cardiomyocyte apoptosis via SIRT1/PGC-1α signaling.

Quercetin potentiates the concurrent hyper-accumulation of cellular biomass and lipids in Chlorella vulgaris

Provision of chemical modulators has emerged as an effective strategy to govern cell growth and development. Here, the impact of flavonoid quercetin on algal growth, lipid accumulation and transcriptional patterns was investigated in the green microalga Chlorella vulgaris. These results demonstrated that quercetin (15 μg/l) significantly enhanced the cellular biomass and photosynthetic efficiency, with up to 2.5-fold in the biomass in the stationary phase. Lipidomic analyses revealed that lipid content was increased by 1.8-fold. Furthermore, the functional mechanism of quercetin on the molecular level was dissected by transcriptomic analysis. Results revealed that quercetin upregulated the expression pattern of key genes involved in cellular signaling mechanisms such as phosphatidylinositol 4-kinase α, thus consequently enhanced cell growth. Altogether, the data present in this study demonstrate the dramatic role of quercetin on enhancing microalgal biomass and lipid accumulation by unprecedented regulation, of key metabolic nodes, for the first time and provide a novel insight into microalgal metabolism and regulation.

Quercetin Oxidation Paradoxically Enhances its Antioxidant and Cytoprotective Properties

Quercetin oxidation is generally believed to ultimately result in the loss of its antioxidant properties. To test this assertion, quercetin oxidation was induced, and after each of its major metabolites was identified and isolated by HPLC-DAD-ESI-MS/MS, the antioxidant (dichlorodihydrofluorescein oxidation-inhibiting) and cytoprotective (LDH leakage-preventing) properties were evaluated in Hs68 and Caco2 cells exposed to indomethacin. Compared to quercetin, the whole mixture of metabolites (Q_OX) displayed a 20-fold greater potency. After resolution of Q_OX into 12 major peaks, only one (peak 8), identified as 2,5,7,3',4'-pentahydroxy-3,4-flavandione or its 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone tautomer, could account for the antioxidant and cytoprotective effects afforded Q_OX. Peak 8 exerted such effects at a 50 nM concentration, revealing a potency 200-fold higher than that of quercetin. The effects of peak 8 were seen regardless of whether it was added to the cells 40 min before or simultaneously with the oxygen-reactive species-generating agent, suggesting an intracellular ability to trigger early antioxidant responses. Thus, the present study is the first to reveal that in regard to the intracellular actions of quercetin, attention should be extended toward some of its oxidation products.

The flavonoid quercetin inhibits titanium dioxide (TiO2)-induced chronic arthritis in mice

Titanium dioxide (TiO₂) is a common component of orthopedic prosthesis. However, prosthesis wear releases TiO₂, which induces inflammation and osteolysis in peri-prosthetic tissues. Quercetin is a flavonoid widely present in human diet, which presents biological activities such as antinociceptive, anti-inflammatory and antioxidant effects. Therefore, the effect of intraperitoneal treatment with quercetin in TiO₂-induced arthritis model was evaluated. In the first set of experiments, mice received injection of TiO₂ (0.1-3 mg/knee joint) and articular mechanical hyperalgesia, edema and histopathology analysis were performed in a 30 days protocol. The dose of 3 mg of TiO₂ showed the most harmful effect, and was chosen to the following experiments. Subsequently, mice received 3 mg of TiO₂ followed by post-treatment with quercetin during 30 days. Quercetin (10-100 mg/kg) inhibited in a dose-dependent manner TiO₂-induced knee joint mechanical hyperalgesia, edema and leukocyte recruitment and did not induce damage in major organs such as liver, kidney and stomach. The dose of 30 mg/kg was chosen for the subsequent analysis, and reduced histopathological changes such as leukocyte infiltration, vascular proliferation and synovial hyperplasia (pannus formation) on day 30 after TiO₂ challenge. The protective analgesic and anti-inflammatory mechanisms of quercetin included the inhibition of TiO₂-induced neutrophil and macrophage recruitment, proteoglycan degradation, oxidative stress, cytokine production (TNF-α, IL-1β, IL-6, and IL-10), COX-2 mRNA expression, and bone resorption as well as activation of Nrf2/HO-1 signaling pathway. These results demonstrate the potential therapeutic applicability of the dietary flavonoid quercetin to reduce pain and inflammatory damages associated with prosthesis wear process-induced arthritis.

Tyrosol and its metabolites as antioxidative and anti-inflammatory molecules in human endothelial cells

Novel biological activities for tyrosol metabolites on human endothelial cells.

Quercetin-3-O-β-D-Glucuronide Suppresses Lipopolysaccharide-Induced JNK and ERK Phosphorylation in LPS-Challenged RAW264.7 Cells

Quercetin, a flavonol, has been reported to exhibit a wide range of biological properties including anti-oxidant and anti-inflammatory activities. However, pharmacological properties of quercetin-3-O-β-D-glucuronide (QG), a glycoside derivative of quercetin, have not been extensively examined. The objective of this study is to elucidate the anti-inflammatory property and underlying mechanism of QG in lipopolysaccharide (LPS)-challenged RAW264.7 macrophage cells in comparison with quercetin. QG significantly suppressed LPS-induced extracellular secretion of pro-inflammatory mediators such as nitric oxide (NO) and PGE₂, and pro-inflammatory protein expressions of iNOS and COX-2. To elucidate the underlying mechanism of the anti-inflammatory property of QG, involvement of MAPK signaling pathways was examined. QG significantly attenuated LPS-induced activation of JNK and ERK in concentration-dependent manners with a negligible effect on p38. In conclusion, the present study demonstrates QG exerts anti-inflammatory activity through the suppression of JNK and ERK signaling pathways in LPS-challenged RAW264.7 macrophage cells.

Therapeutic Potential of Polyphenols from Epilobium Angustifolium (Fireweed)

Epilobium angustifolium is a medicinal plant used around the world in traditional medicine for the treatment of many disorders and ailments. Experimental studies have demonstrated that Epilobium extracts possess a broad range of pharmacological and therapeutic effects, including antioxidant, anti-proliferative, anti-inflammatory, antibacterial, and anti-aging properties. Flavonoids and ellagitannins, such as oenothein B, are among the compounds considered to be the primary biologically active components in Epilobium extracts. In this review, we focus on the biological properties and the potential clinical usefulness of oenothein B, flavonoids, and other polyphenols derived from E. angustifolium. Understanding the biochemical properties and therapeutic effects of polyphenols present in E. angustifolium extracts will benefit further development of therapeutic treatments from this plant. Copyright © 2016 John Wiley & Sons, Ltd.

Bu-Shen-Ning-Xin Decoction ameliorated the osteoporotic phenotype of ovariectomized mice without affecting the serum estrogen concentration or uterus

INTRODUCTION

Bu-Shen-Ning-Xin Decoction (BSNXD), a traditional Chinese medicinal composition, has been used as a remedy for postmenopausal osteoporosis, but its effects on bone metabolism and the uterus have not been reported.

PURPOSE

We aimed to determine the respective effects of BSNXD on the bones and the uterus of ovariectomized (OVX) mice to evaluate the efficacy and safety of this herbal formula.

MATERIALS AND METHODS

Postmenopausal osteoporosis animal models that were generated by ovariectomy were treated with BSNXD. Dual-energy X-ray absorptiometry was performed to analyze the bone mineral density, and histomorphometric analysis was performed to measure the parameters related to bone metabolism. Calcein labeling was performed to detect bone formation. The uteruses from the mice were weighed, and the histomorphometry was analyzed. Drug-derived serum was prepared to assess the 17-β-estradiol concentration via enzyme immunoassay.

RESULTS

BSNXD administration ameliorated the osteoporotic phenotype of OVX mice, as evidenced by an increase in the bone mineral density and bone volume; these effects could not be abolished by the administration of the aromatase inhibitor letrozole. Moreover, BSNXD had no effect on the serum estrogen concentration or uterus.

CONCLUSION

These results suggest that BSNXD has ameliorating effects on bone loss due to estrogen deprivation without affecting the peripheral blood estrogen concentration or the uterus in OVX mice.