Validation of stability-indicating LC method, degradation study, and impact on antioxidant and antifungal activities of Eugenia uniflora leaves extract

The aim of this study is to demonstrate the stability-indicating capacity of an analytical method for Eugenia uniflora, enhance understanding of the stability of myricitrin, and assess the effect of degradation of spray-dried extract (SDE) on antioxidant and antifungal activities. Validation of the stability-indicating method was carried out through a forced degradation study of SDE and standard myricitrin. The antioxidant and antifungal activities of SDE were evaluated both before and after degradation. The quantification method described was found to be both accurate and precise in measuring myricitrin levels in SDE from E. uniflora, with excellent selectivity that confirmed its stability-indicating capability. The forced degradation study revealed that the marker myricitrin is sensitive to hydrolysis, but generally stable under other stress conditions. By contrast, the standard myricitrin displayed greater susceptibility to degradation under forced degradation conditions. Analysis of the antioxidant activity of SDE before and after degradation showed a negative impact in this activity due to degradation, while no significant effect was observed on antifungal activity. The method described can be a valuable tool in the quality control of E. uniflora, and the findings can assist in determining the optimal conditions and storage of products derived from this species.

Kinetics of Flavonoid Degradation and Controlled Release from Functionalized Magnetic Nanoparticles

Flavonoids are naturally occurring antioxidants that have been shown to protect cell membranes from oxidative stress and have a potential use in photodynamic cancer treatment. However, they degrade at physiological pH values, which is often neglected in drug release studies. Kinetic study of flavonoid oxidation can help to understand the mechanism of degradation and to correctly analyze flavonoid release data. Additionally, the incorporation of flavonoids into magnetic nanocarriers can be utilized to mitigate degradation and overcome their low solubility, while the release can be controlled using magnetic fields (MFs). An approach that combines alternating least squares (ALS) and multilinear regression to consider flavonoid autoxidation in release studies is presented. This approach can be used in general cases to account for the degradation of unstable drugs released from nanoparticles. The oxidation of quercetin, myricetin (MCE), and myricitrin (MCI) was studied in PBS buffer (pH = 7.4) using UV-vis spectrophotometry. ALS was used to determine the kinetic profiles and characteristic spectra, which were used to analyze UV-vis data of release from functionalized magnetic nanoparticles (MNPs). MNPs were selected for their unique magnetic properties, which can be exploited for both targeted drug delivery and control over the drug release. MNPs were prepared and characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, superconducting quantum interference device magnetometer, and electrophoretic mobility measurements. Autoxidation of all three flavonoids follows a two-step first-order kinetic model. MCE showed the fastest degradation, while the oxidation of MCI was the slowest. The flavonoids were successfully loaded into the prepared MNPs, and the drug release was described by the first-order and Korsmeyer-Peppas models. External MFs were utilized to control the release mechanism and the cumulative mass of the flavonoids released.

Myricitrin promotes osteogenesis and prevents ovariectomy bone mass loss via the PI3K/AKT signalling pathway

This study aimed to explore the effect of myricitrin on osteoblast differentiation in mice immortalised bone marrow mesenchymal stem cells (imBMSCs). Additionally, ovariectomy (OVX) mice were employed to examine the effect of myricitrin on bone trabecular loss in vivo. The effect of myricitrin on the proliferation of imBMSCs was evaluated using a cell counting kit-8 assay. Alizarin red staining, alkaline phosphatase staining were performed to elucidate osteogenesis. Furthermore, qRT-PCR and western blot determined the expression of osteo-specific genes and proteins. To screen for candidate targets, mRNA transcriptome genes were sequenced using bioinformatics analyses. Western blot and molecular docking analysis were used to examine target signalling markers. Moreover, rescue experiments were used to confirm the effect of myricitrin on the osteogenic differentiation of imBMSCs. OVX mice were also used to estimate the delay capability of myricitrin on bone trabecular loss in vivo using western blot, micro-CT, tartaric acid phosphatase (Trap) staining, haematoxylin and eosin staining, Masson staining and immunochemistry. In vitro, myricitrin significantly enhanced osteo-specific genes and protein expression and calcium deposition. Moreover, mRNA transcriptome gene sequencing and molecular docking analysis revealed that this enhancement was accompanied by an upregulation of the PI3K/AKT signalling pathway. Furthermore, copanlisib, a PI3K inhibitor, partially reversed the osteogenesis promotion induced by myricitrin. In vivo, western blot, micro-CT, hematoxylin and eosin staining, Masson staining, Trap staining and immunochemistry revealed that bone trabecular loss rate was significantly alleviated in the myricitrin low- and high-dose groups, with an increased expression of osteopontin, osteoprotegerin, p-PI3K and p-AKT compared to the OVX group. Myricitrin enhances imBMSC osteoblast differentiation and attenuate bone mass loss partly through the upregulation of the PI3K/AKT signalling pathway. Thus, myricitrin has therapeutic potential as an antiosteoporosis drug.

Hepatoprotective role of myricitrin isolated from Mimusops elengi Linn. leaves extract on γ-radiation-induced liver damage in rats: Phyto-biochemical investigations

The hepatoprotective effects of methanol extract of Mimusops elengi Linn. (M. elengi L.) leaves and isolated pure myricitrin (3-, 4-, 5-, 5, 7-five hydroxyflavone-3-O-α-l-rhamnoside) (Myr) were evaluated in male rats exposed to γ-irradiation. The extraction of M. elengi L. leaves was performed using ethyl acetate (EtOAC). Seven groups of rats were used: control group, irradiated (IRR) group (6 Gy of γ-rays in a single dose), vehicle group (oral administration of 0.5% carboxymethyl cellulose for 10 days), EtOAC extract group (100 mg/kg body weight of extract, orally for 10 days), EtOAC + IRR group (administration of extract and exposure to γ-rays on Day 7), Myr group (50 mg/kg body weight Myr, orally for 10 days), and Myr + IRR group (administration of Myr and exposure to γ-rays on Day 7). High-performance liquid chromatography and 1H-nuclear magnetic resonance were used to isolate and characterize the compounds from M. elengi L. leaves. Enzyme-linked immunosorbent assay was used for biochemical analyses. Identified compounds were Myr, myricetin 3-O-galactoside, myricetin 3-O-rahmnopyranoside (1 → 6) glucopyranoside, quercetin, quercitol, gallic acid, α-,β-amyrin, ursolic acid, and lupeol. Serum aspartate transaminase and alanine transaminase activities were significantly increased, while serum protein and albumin levels were significantly decreased after irradiation. Hepatic levels of tumor necrosis factor-α, prostaglandin 2, inducible nitric oxide synthase, interleukin-6 (IL-6), and IL-12 were increased following irradiation. Improvements were observed in most serological parameters after treatment with extract or pure Myr, with histological analyses confirming decreased liver injury in treated rats. Our study demonstrates that pure Myr has a greater hepatoprotective effect than M. elengi leaf extracts against irradiation-induced hepatic inflammation.

Toward the bioactive potential of myricitrin in food production: state-of-the-art green extraction and trends in biosynthesis

Myricitrin is a member of flavonols, natural phenolic compounds extracted from plant resources. It has gained great attention for various biological activities, such as anti-inflammatory, anti-cancer, anti-diabetic, as well as cardio-/neuro-/hepatoprotective activities. These effects have been demonstrated in both in vitro and in vivo models, making myricitrin a favorable candidate for the exploitation of novel functional foods with potential protective or preventive effects against diseases. This review summarized the health benefits of myricitrin and attempted to uncover its action mechanism, expecting to provide a theoretical basis for their application. Despite enormous bioactive potential of myricitrin, low production, high cost, and environmental damage caused by extracting it from plant resources greatly constrain its practical application. Fortunately, innovative, green, and sustainable extraction techniques are emerging to extract myricitrin, which function as alternatives to conventional techniques. Additionally, biosynthesis based on synthetic biology plays an essential role in industrial-scale manufacturing, which has not been reported for myricitrin exclusively. The construction of microbial cell factories is absolutely an appealing and competitive option to produce myricitrin in large-scale manufacturing. Consequently, state-of-the-art green extraction techniques and trends in biosynthesis were reviewed and discussed to endow an innovative perspective for the large-scale production of myricitrin.

Diospyros lotus leaf extract and its main component myricitrin regulate pruritus through the inhibition of astrocyte activation

Diospyros lotus is a deciduous plant native to Asian countries, including Korea, Japan and China, and southeast Europe. In traditional medicine, Diospyros lotus is used as an anticancer, antidiabetic and antipyretic agent. The present study aimed to evaluate the effect of Diospyros lotus leaf extract (DLE) in ameliorating histamine-independent pruritus. Activation of signal transducer and activator of transcription 3 (STAT3) in astrocytes contributes to pruritus. In this study, the effects of DLE and its main component, myricetin (MC), on the activation of STAT3, expression of glial fibrillary acidic protein (GFAP), and production of lipocalin-2 (LCN2) in IL-6-treated astrocytes and chloroquine-injected mice were investigated through western blot, reverse transcription-quantitative PCR, and immunofluorescence staining. DLE and MC inhibited STAT3 activation, GFAP expression and LCN2 release via inositol 1,4,5-trisphosphate receptor type 1 blockade in astrocytes. DLE and MC ameliorated scratching behavior, expression of GFAP, mast cell infiltration and serum IL-6 levels in chloroquine-injected mice. These results suggested that DLE and MC can be used as oral therapeutic agents for the treatment and management of pruritus.

Hyperglycemia-induced oxidative stress in isolated proximal tubules of mouse: the in vitro effects of myricitrin and its solid lipid nanoparticle

CONTEXT

The hyperglycemia (Hyper) induces oxidative stress in kidney tubular cells. Myricitrin (Myr) has an antioxidant effect along with low bioavailability.

OBJECTIVE

The present research investigated the effects of Myr and its solid lipid nanoparticles (SLN) on isolated proximal tubules exposed to the hyperglycemic condition.

MATERIALS AND METHODS

In this experimental study, the proximal tubules of mice were dissected by the microdissection method and the tubules were prepared for experimental or Real Time-PCR measurement.

RESULTS

The malondialdehyde level, transforming growth factor-β, nuclear factor kappa B and Bax genes expression increased in Hyper and decreased in Hyper + Myr and its SLN-treated groups compared to Hyper. Superoxide dismutase, total antioxidant capacity, the viability of proximal tubules and Bcl-2 gene expression decreased in untreated Hyper and increased in all treatment groups compared to Hyper.

CONCLUSION

The hyperglycemia-induced oxidative disorder, inflammation and apoptosis in proximal tubules and that administrating Myr and its SLN improved them.

Evaluation of Semi-Solid-State Fermentation of Elaeocarpus serratus L. Leaves and Black Soymilk by Lactobacillus plantarum on Bioactive Compounds and Antioxidant Capacity

Elaeocarpus serratus L. leaves (EL) containing phenolic compounds and flavonoids, including myricitrin with pharmacological properties, could be valorized as nutritional additive in foods. In this study, the semi-solid-state fermentation of EL and black soymilk (BS) by Lactobacillus plantarum BCRC 10357 was investigated. Without adding EL in MRS medium, the β-glucosidase activity of L. plantarum quickly reduced to 2.33 ± 0.15 U/mL in 36 h of fermentation; by using 3% EL, the stability period of β-glucosidase activity was prolonged as 12.94 ± 0.69 U/mL in 12 h to 13.71 ± 0.94 in 36 h, showing positive response of the bacteria encountering EL. Using L. plantarum to ferment BS with 3% EL, the β-glucosidase activity increased to 23.78 ± 1.34 U/mL in 24 h, and in the fermented product extract (FPE), the content of myricitrin (2297.06 μg/g-FPE) and isoflavone aglycones (daidzein and genistein, 474.47 μg/g-FPE) at 48 h of fermentation were 1.61-fold and 1.95-fold of that before fermentation (at 0 h), respectively. Total flavonoid content, myricitrin, and ferric reducing antioxidant power in FPE using BS and EL were higher than that using EL alone. This study developed the potential fermented product of black soymilk using EL as a nutritional supplement with probiotics.

Myricitrin, a Glycosyloxyflavone in Myrica esculenta Bark Ameliorates Diabetic Nephropathy via Improving Glycemic Status, Reducing Oxidative Stress, and Suppressing Inflammation

The present study evaluated the therapeutic potential of myricitrin (Myr), a glycosyloxyflavone extracted from Myrica esculenta bark, against diabetic nephropathy. Myr exhibited a significant hypoglycemic effect in high fat-fed and a single low-dose streptozotocin-induced type 2 diabetic (T2D) rats. Myr was found to improve glucose uptake by the skeletal muscle via activating IRS-1/PI3K/Akt/GLUT4 signaling in vitro and in vivo. Myr significantly attenuated high glucose (HG)-induced toxicity in NRK cells and in the kidneys of T2D rats. In this study, hyperglycemia caused nephrotoxicity via endorsing oxidative stress and inflammation resulting in the induction of apoptosis, fibrosis, and inflammatory damages. Myr was found to attenuate oxidative stress via scavenging/neutralizing oxidative radicals and improving endogenous redox defense through Nrf-2 activation in both in vitro and in vivo systems. Myr was also found to attenuate diabetes-triggered renal inflammation via suppressing NF-κB activation. Myr inhibited hyperglycemia-induced apoptosis and fibrosis in renal cells evidenced by the changes in the expressions of the apoptotic and fibrotic factors. The molecular docking predicted the interactions between Myr and different signal proteins. An in silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) study predicted the drug-likeness character of Myr. Results suggested the possibility of Myr to be a potential therapeutic agent for diabetic nephropathy in the future.

Phytochemicals with Added Value from Morella and Myrica Species

Terrestrial plants, due to their sessile nature, are highly exposed to environmental pressure and therefore need to produce very effective molecules that enable them to survive all the threats. Myrica and Morella (Myricaceae) are taxonomically close genera, which include species of trees or shrubs with edible fruits that exhibit relevant uses in traditional medicine. For instance, in Chinese or Japanese folk medicine, they are used to treat diarrhea, digestive problems, headache, burns, and skin diseases. A wide array of compounds isolated from different parts of Myrica and/or Morella species possess several biological activities, like anticancer, antidiabetic, anti-obesity, and cardio-/neuro-/hepatoprotective activities, both in vitro and in vivo, with myricanol, myricitrin, quercitrin, and betulin being the most promising. There are still many other compounds isolated from both genera whose biological activities have not been evaluated, which represents an excellent opportunity to discover new applications for those compounds and valorize Morella/Myrica species.

Ethyl acetate extract from Cistus x incanus L. leaves enriched in myricetin and quercetin derivatives, inhibits inflammatory mediators and activates Nrf2/HO-1 pathway in LPS-stimulated RAW 264.7 macrophages

Cistus x incanus L. is a Mediterranean evergreen shrub used in folk medicine for the treatment of inflammatory disorders but the underlying mechanisms are not fully understood. We therefore investigated the anti-inflammatory effects of an ethyl acetate fraction (EAF) from C. x incanus L. leaves on lipopolysaccharide (LPS) activated RAW 264.7 macrophages. HPLC analysis revealed myricetin and quercetin derivatives to be the major compounds in EAF; EAF up to 1 µM of total phenolic content, was not cytotoxic and inhibited the mRNA expression of interleukin-6 (IL-6) and cyclooxygenase-2 (COX-2) (p < 0.05) and the production of prostaglandins E₂ (PGE₂) (p < 0.05). Meanwhile, EAF triggered the mRNA expression of interleukin-10 (IL-10) and elicited the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), as well as the expression of its main target gene, heme oxygenase-1 (HO-1) (p < 0.05). These data indicate that EAF attenuates experimental inflammation via the inhibition of proinflammatory mediators and at least in part, by the activation of Nrf2/HO-1 pathway. These effects are likely due to myricetin and quercetin derivatives but the role of other, less abundant components cannot be excluded. Further studies to confirm the relevance of our findings in animal models and to highlight the relative contribution of each component to the anti-inflammatory activity of EAF should be conducted.

Myricitrin attenuates memory impairment in a rat model of sepsis-associated encephalopathy via the NLRP3/Bax/Bcl pathway

INTRODUCTION

The present investigation determined the protective effect of myricitrin against sepsis-associated encephalopathy in rats.

MATERIAL AND METHODS

Sepsis was induced by cecal ligation and puncture (CLP); rats were treated with 30 or 100 mg/kg of myricitrin for 5 days prior to the induction of CLP. The effect of myricitrin was observed by determining the neurological function using the open field test and step-down inhibitory avoidance test. Cerebral oedema and the levels of inflammatory and oxidative stress mediators were determined in brain tissues. Moreover, the expression levels of Bcl-2, Bax, IκB-α, nuclear factor κB (NF-κB), caspase-3 and NLRP3 were estimated in brain tissues by Western blotting and the mRNA expression of NF-κB, caspase-3 and NLRP3 in brain tissues was estimated by real-time polymerase chain reaction. An immunofluorescence assay was performed to estimate inflammasome activity.

RESULTS

The results suggest that treatment with myricitrin protects neuronal function in rats with CLP-induced sepsis. Decreases in inflammation and oxidative stress mediators were observed in the brain tissues of the myricitrin-treated group compared to the CLP group. Moreover, treatment with myricitrin ameliorated the altered Bcl-2, Bax, IκB-α, NF-κB, caspase-3 and NLRP3 protein and mRNA expression levels in the brain tissues of septic rats.

CONCLUSIONS

The data reveal that myricitrin ameliorated neuroinflammation and improved memory in rats with CLP-induced sepsis by regulating the NLRP3/Bax/Bcl signalling pathway.

Isolation and characterization of flavonoids from Tapirira guianensis leaves with vasodilatory and myeloperoxidase-inhibitory activities

The aim of this study was to perform the isolation and characterization of vasodilatory flavonoids from Tapirira guianensis Aubl. (Annacardiaceae) leaves. In this context, ethyl acetate fraction (EA fraction) was obtained and subjected to fractionation batches by HSCCC affording: myricetin 3-O-α-L-rhamnopyranoside (myricitrin, 1); quercetin 3-O-(6"-O-galloyl)-β-D-galactopyranoside (2); quercetin 3-O-α-L-arabinofuranoside (avicularin, 3); and quercetin 3-O-α-L-rhamnopyranoside (quercitrin, 4). Myricitrin (1) induced a relaxation of 56.07 ± 13.04% at 300 μM (P < 0.05; n = 5), indicating that this flavonoid contributes to the vasodilatory activity of EA fraction. In addition, all EA fraction flavonoids were evaluated for their capacity of inhibiting myeloperoxidase activity and flavonoid (2) (IC₅₀ 1.0 ± 0.3 µM) was the strongest peroxidase inhibitor. In conclusion, it was possible to verify that myricitrin together with quercetin are mainly responsible for vasodilatory potential, besides flavonoid 2 for myeloperoxidase inhibition. Together these flavonoids seem to be responsible for Tapirira guianensis cardiovascular effects.

The Structural Integrity of the Model Lipid Membrane during Induced Lipid Peroxidation: The Role of Flavonols in the Inhibition of Lipid Peroxidation

The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.

Myricitrin Ameliorates Hyperglycemia, Glucose Intolerance, Hepatic Steatosis, and Inflammation in High-Fat Diet/Streptozotocin-Induced Diabetic Mice

To test the hypothesis that myricitrin (MYR) improves type 2 diabetes, we examined the effect of MYR on hyperglycemia, glucose intolerance, hepatic steatosis, and inflammation in high-fat diet (HFD) and streptozotocin (STZ)-induced type 2 diabetic mice. Male C57BL/6J mice were randomly divided into three groups: non-diabetic, diabetic control, and MYR (0.005%, w/w)-supplemented diabetic groups. Diabetes was induced by HFD and STZ, and MYR was administered orally for 5 weeks. Myricitrin exerted no significant effects on food intake, body weight, fat weight, or plasma lipids levels. However, MYR significantly decreased fasting blood glucose levels, improved glucose intolerance, and increased pancreatic β-cell mass compared to the diabetic control group. Myricitrin administration also markedly increased glucokinase mRNA expression and activity as well as lowered glucose-6-phosphatase and phosphoenolpyruvate carboxykinase mRNA expression and activity in the liver. In addition, liver weight, hepatic triglyceride content, and lipid droplet accumulation were markedly decreased following MYR administration. These changes were seemingly attributable to the suppression of the hepatic lipogenic enzymes—fatty acid synthase and phosphatidate phosphohydrolase. Myricitrin also significantly lowered plasma MCP-1 and TNF-α levels and the mRNA expression of hepatic pro-inflammatory genes. These results suggest that MYR has anti-diabetic potential.

Study on the Material Basis of Neuroprotection of Myrica rubra Bark

Background: Increasing attention has been given to the search for neuroprotective ingredients from natural plants. Myrica rubra bark (MRB) has been used in traditional oriental medicine for over thousand years and has potential neuroprotection. Methods and Results: Ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was used to identify the compounds in MRB extract, and the MTT assay was performed to evaluate the neuroprotection of six major compounds from MRB against glutamate-induced damage in PC12 cells. The result displayed nineteen compounds were identified, and myricitrin and myricanol 11-sulfate were shown to have neuroprotection, which prevented cell apoptosis through alleviating oxidative stress by reducing the levels of reactive oxygen species and methane dicarboxylic aldehyde, as well as by enhancing the activities of superoxide dismutase. Conclusions: Several active compounds from MRB may offer neuroprotection and have the potential for the development of new drugs against central nervous system diseases.

Enhanced Protection of Biological Membranes during Lipid Peroxidation: Study of the Interactions between Flavonoid Loaded Mesoporous Silica Nanoparticles and Model Cell Membranes

Flavonoids, polyphenols with anti-oxidative activity have high potential as novel therapeutics for neurodegenerative disease, but their applicability is rendered by their poor water solubility and chemical instability under physiological conditions. In this study, this is overcome by delivering flavonoids to model cell membranes (unsaturated DOPC) using prepared and characterized biodegradable mesoporous silica nanoparticles, MSNs. Quercetin, myricetin and myricitrin have been investigated in order to determine the relationship between flavonoid structure and protective activity towards oxidative stress, i.e., lipid peroxidation induced by the addition of hydrogen peroxide and/or Cu²⁺ ions. Among investigated flavonoids, quercetin showed the most enhanced and prolonged protective anti-oxidative activity. The nanomechanical (Young modulus) measurement of the MSNs treated DOPC membranes during lipid peroxidation confirmed attenuated membrane damage. By applying a combination of experimental techniques (atomic force microscopy—AFM, force spectroscopy, electrophoretic light scattering—ES and dynamic light scattering—DLS), this work generated detailed knowledge about the effects of flavonoid loaded MSNs on the elasticity of model membranes, especially under oxidative stress conditions. Results from this study will pave the way towards the development of innovative and improved markers for oxidative stress-associated neurological disorders. In addition, the obtained could be extended to designing effective delivery systems of other high potential bioactive molecules with an aim to improve human health in general.

Isolation of Myricitrin and 3,5-di-O-Methyl Gossypetin from Syzygium samarangense and Evaluation of their Involvement in Protecting Keratinocytes against Oxidative Stress via Activation of the Nrf-2 Pathway

The wax apple (Syzygium samarangense) is traditionally employed as an antibacterial and immunostimulant drug in traditional medicine. This plant is rich in different flavonoids and tannins. In this study, we isolated two compounds from S. samarangense leaves: myricitrin and 3,5-di-O-methyl gossypetin. Then, we investigated the mechanisms of action of the two compounds against oxidative stress (induced by sodium arsenite) and inflammation (induced by UV light) on human keratinocytes. We could clearly demonstrate that the pre-treatment of cells with both compounds was able to mitigate the negative effects induced by oxidative stress, as no alteration in reactive oxygen species (ROS) production, glutathione (GSH) level, or protein oxidation was observed. Additionally, both compounds were able to modulate mitogen-activated protein kinase (MAPK) signaling pathways to counteract oxidative stress activation. Finally, we showed that 3,5-di-O-methyl gossypetin exerted its antioxidant activity through the nuclear transcription factor-2 (Nrf-2) pathway, stimulating the expression of antioxidant proteins, such as HO-1 and Mn-SOD-3.

Isolation and Identification of Myricitrin, an Antioxidant Flavonoid, from Daebong Persimmon Peel

In this study, the antioxidant flavonoid, myricitrin, was isolated and identified from Daebong persimmon peel. The persimmon peel extract was successively fractionated with n-hexane, ethyl acetate, and n-butanol. The ethyl acetate fraction had the strongest antioxidant activities among the solvent fractions and was further fractionated by silica gel and octadecylsilane column chromatography, and preparative high performance liquid chromatography. Three antioxidant compounds were finally isolated, and compound 2 was identified as myricitrin by liquid chromatography/mass spectrometry and ¹H and ¹³C nuclear magnetic resonance. Myricitrin had the strongest antioxidant activities by ferric ion reducing antioxidant power and α,α-diphenyl-2-picrylhydrazyl radical scavenging assays. These results suggested that myricitrin was found as a major antioxidant flavonoid responsible for the strong antioxidant activities of Daebong persimmon peels.

Inhibition effects of a natural inhibitor on RANKL downstream cellular signalling cascades cross-talking

Myricitrin is a natural occurring flavonoid glycoside that possesses effects on inhibiting nitric oxide (NO) transmission and preventing inflammatory reaction. Although previous study showed the myricitrin possesses antibone loss effects via reducing the expression of IL-6 and partially suppressing reactive oxygen species (ROS) production. However, the effects of myricitrin on nuclear factor-kappaB ligand (RANKL)-stimulated osteoclastogenesis have not yet been further investigated. The current study was aimed to demonstrating the inhibitory effects of myricitrin on RANKL-stimulated osteoclastogenesis and relevant mechanisms. We found myricitrin significantly suppressed osteoclastogenesis suggesting that it may acts on RANKL/RANK induced downstream signal cross cascading in osteoclast precursors. In that, our Western blotting results showed myricitrin significantly attenuated RNAKL/MAPKs (phosphorylation of p38, ERK, JNK) and AKT signal cascading. Complementing previous study, our results suggesting as a natural inhibitor, myricitrin possesses the potential therapeutic effects on inflammatory osteolysis.

New Pharmacological Approaches Using Polyphenols on the Physiopathology of Neuropathic Pain

Polyphenols constitute a group of a paramount importance within the natural products in the plant kingdom, with an approximate amount of 8000 phenolic structures currently known. Fruits, vegetables, whole grains and several other foods and beverages (as tea, chocolate and wine, for instance) are rich and important sources of polyphenols. The scientific literature provides pre-clinical experimental evidence on the antinociceptive effects of polyphenolic compounds, found in plant extracts, in animal models of neuropathic pain. But not only neuropathic pain is attenuated: in fact, nociceptive pain, caused by stimulation of nerve fibers (either somatic or visceral) responding only to stimuli approaching or exceeding harmful intensity thresholds (nociceptors), and also inflammatory pain, which is associated with tissue damage and infiltration of immune cells, are both reduced and alleviated by polyphenols. In the present work, the antinociceptive effects of polyphenols are reviewed.

Myricitrin Protects Cardiomyocytes from Hypoxia/Reoxygenation Injury: Involvement of Heat Shock Protein 90

Modulation of oxidative stress is therapeutically effective in ischemia/reperfusion (I/R) injury. Myricitrin, a naturally occurring phenolic compound, is a potent antioxidant. However, little is known about its effect on I/R injury to cardiac myocytes. The present study was performed to investigate the potential protective effect of myricitrin against hypoxia/reoxygenation (H/R)-induced H9c2 cardiomyocyte injury and its underlying mechanisms. Myricitrin pretreatment improved cardiomyocyte viability, inhibited ROS generation, maintained the mitochondrial membrane potential, reduced apoptotic cardiomyocytes, decreased the caspase-3 activity, upregulated antiapoptotic proteins and downregulated proapoptotic proteins during H/R injury. Moreover, the potential targets of myricitrin was predicted using Discovery Studio software, and heat shock protein 90 (Hsp90) was identified as the main disease-related target. Further mechanistic investigation revealed that 17-AAG, a pharmacologic inhibitor of Hsp90, significantly blocked the myricitrin-induced cardioprotective effect demonstrated by increased apoptosis and ROS generation. These results suggested that myricitrin provides protection to H9c2 cardiomyocytes against H/R-induced oxidative stress and apoptosis, most likely via increased expression of Hsp90.

Gastrointestinal stability of dihydromyricetin, myricetin, and myricitrin: an in vitro investigation

The gastrointestinal (GI) stability of three flavonoids, dihydromyricetin (DMY), myricetin (MYR), and myricitrin (MYT), was examined in simulated physiological fluids. Several factors that may influence the degradation rate of theses flavonoids were evaluated, including pH and the presence of pepsin and pancreatin enzymes. We found that GI stability followed the order of MYT > DMY > MYR. These flavonoids were stable in simulated gastric fluids and buffer solutions (pH 1.2), but encountered a pseudo-first-order kinetic degradation in simulated intestinal fluids and buffer solutions (pH 6.8). We conclude that it is the pH, rather than the presence of pepsin or pancreatin, which most strongly influences the stability of these three flavonoids. Further study of the stability of the compounds using a pH range (1.0-8.0) indicated potential instability in the duodenum, small intestine, and colon. Therefore, we conclude that the low bioavailability of these flavonoids may be due to their poor stability in the GI tract.

Identification of the metabolites of myricitrin produced by human intestinal bacteria in vitro using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry

OBJECTIVE

To investigate the metabolic routes and metabolites of myricitrin, an important active ingredient of traditional herbal medicine, yielded by the isolated human intestinal bacteria, which have not been reported previously.

METHODS

Fresh human fecal samples were collected from a healthy female volunteer and about 100 different bacterial colonies were isolated. Ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry technique combined with Metabolynx™ software was used for analysis of the metabolic profile of myricitrin by the isolated human intestinal bacteria.

RESULTS

One hundred different bacterial colonies, which developed on plates, were picked up, and four of them were further identified by using the technique of 16S rRNA gene sequencing due to their relatively strong metabolic capacity toward myricitrin. Most of them belong to Escherichia. Parent compound and three metabolites (quercetin-3-O-rhamnoside, myricetin and quercetin) were detected in the isolated bacterial samples compared with blank samples. The metabolic pathways of myricitrin included deglycosylation and dehydroxylation.

CONCLUSIONS

These metabolites suggested that myricitrin was first dehydroxylated to quercetin-3-O-rhamnoside and subsequently deglycosylated to quercetin. Additionally, myricitrin could also be deglycosylated to the aglycon myricetin. Moreover, those metabolites might influence the biological effect of myricitrin in vivo, which led to affect the clinical effects of the medicinal plants and traditional herb medicines.