MEK1; PI3Kγ (Kd = 0.17 μM)

Myricetin(Cannabiscetin) is a flavonoid with antioxidant and anti-tumor properties that can be found in a variety of plants, including grapes, berries, fruits, vegetables, herbs, and other plants. The antioxidant properties of myricetin. High concentrations of myricetin may modify LDL cholesterol in a way that increases uptake by white blood cells, according to in vitro research. [1] According to studies, a high myricetin intake lowers the risk of pancreatic and prostate cancer. [2] [3]

Orthotopic tumor kinases treated with myricetin exhibit regression and reduced proliferation [2]. ADP, arachidonic acid, collagen, PAF, and 14%, 26%, 5%, and 49% of rabbits were found to have tumors localized in rabbits subjected to 150 μM myricetin, respectively [5].

Myricetin (12.5-200 μM) is used to treat pancreatic cancer cells (MIA PaCa-2, Panc-1, or S2-013) or healthy pancreatic ductal cells (PDCs). Dojindo Cell Counting Kit-8 is used to assess cell viability. 1×104 cells are seeded into each well of a 96-well plate, and the cells are left to adhere for the night. Ten microliters of the tetrazolium substrate are added to each well of the plate after myricetin treatments at various concentrations were given for 24 hours. The absorbance at 450 nm is measured after plates have been incubated at 37°C for an hour.

Mice: For 35 days (MIA PaCa-2 model) or 18 days (S2-013 model), mice receive daily intraperitoneal injections of myricetin (30 mg/kg in the MIA PaCa-2 model and 50 mg/kg in the S2-013 model) or a vehicle (DMSO). To track tumor growth, ultrasound measurements are taken on a regular basis. At the conclusion of the in vivo experiment, the tumor volume and size are calculated[2].

Absorption, Distribution and Excretion
... Significant quantities of quercetin and possibly myricetin and kaempferol are absorbed in the gut. A larger fraction probably remains in the lumen, and thus a substantial proportion of the gastrointestinal mucosa is exposed to biologically significant concentrations of these compounds. ...

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Metabolism / Metabolites
Myricetin has known human metabolites that include (2S,3S,4S,5R)-6-[5,7-Dihydroxy-4-oxo-2-(3,4,5-trihydroxyphenyl)chromen-3-yl]oxy-3,4,5-trihydroxyoxane-2-carboxylic acid.

Interactions
... Addition of apigenin, chrysin, fisetin, flavonone, galangin, hesperitin, kaempferol, morin, myricetin, haringenin, or quercetin to human liver microsomes inhibited the hydroxylation of benzo(a)pyrene. In contrast to these results, the addition of flavone, nobiletin, tangeretin, or 7,8-benzoflavone to human liver microsomes caused a many-fold stimulation in the hydroxylation of benzo(a)pyrene, the metabolism of aflatoxin B1 to 2,3-dihydro-2,3-dihydroxyaflatoxin B1, and the metabolic activation of aflatoxin B1 to mutagenic products. ... An examination of the structural features required for the inhibition and stimulation of benzo(a)pyrene hydroxylation indicated that all of the 12 flavonoid inhibitors that were studied possessed hydroxyl groups whereas the flavonoid activators were less polar molecules that lacked hydroxyl groups.
... Myricetin suppresses UVB-induced cyclooxygenase-2 (COX-2) expression in mouse skin epidermal JB6 P+ cells. The activation of activator protein-1 and nuclear factor-kappaB induced by UVB was dose-dependently inhibited by myricetin treatment. Western blot and kinase assay data revealed that myricetin inhibited Fyn kinase activity and subsequently attenuated UVB-induced phosphorylation of mitogen-activated protein kinases. Pull-down assays revealed that myricetin competitively bound with ATP to suppress Fyn kinase activity. Importantly, myricetin exerted similar inhibitory effects compared with 4-amino-5-(4-chloro-phenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, a well-known pharmacologic inhibitor of Fyn. In vivo mouse skin data also revealed that myricetin inhibited Fyn kinase activity directly and subsequently attenuated UVB-induced COX-2 expression. Mouse skin tumorigenesis data clearly showed that pretreatment with myricetin significantly suppressed UVB-induced skin tumor incidence in a dose-dependent manner. Docking data suggest that myricetin is easily docked to the ATP-binding site of Fyn, which is located between the N and C lobes of the kinase domain. Overall, these results indicated that myricetin exerts potent chemopreventive activity mainly by targeting Fyn in skin carcinogenesis.
... Bor-tezomib is a dipeptide boronate proteasome inhibitor that has activity in the treatment of multiple myeloma but is not effective in chronic lymphocytic leukemia (CLL). Although CLL cells are sensitive in vitro to bortezomib-induced apoptosis when cultured in medium, the killing activity was blocked when cultured in 50% fresh autologous plasma. Dietary flavonoids, quercetin and myricetin, which are abundant in plasma, inhibited bortezomib-induced apoptosis of primary CLL and malignant B-cell lines in a dose-dependent manner...
The purpose of this study was to investigate the potential neuroprotective effects of myricetin (flavonoid) and fraxetin (coumarin) on rotenone-induced apoptosis in SH-SY5Y cells, and the possible signal pathway involved in a neuronal cell model of Parkinson's disease. ... Rotenone caused a time- and dose-dependent decrease in cell viability and the degree of LDH release was proportionally to the effects on cell viability. Cells were pretreated with fraxetin, myricetin and N-acetylcysteine at different concentrations for 30 min before exposure to rotenone. Cytotoxicity of rotenone (5 uM) for 16 hr was significantly diminished as well as the release of LDH into the medium, by the effect of fraxetin, myricetin and N-acetylcysteine, with fraxetin (100 uM) and N-acetylcysteine (100 uM) being more effective than myricetin (50 uM)...
The effects of myricetin on either MRP1 or MRP2 mediated vincristine resistance in transfected MDCKII cells were examined. The results obtained show that myricetin can inhibit both MRP1 and MRP2 mediated vincristine efflux in a concentration dependent manner. The IC50 values for cellular vincristine transport inhibition by myricetin were 30.5+/-1.7 uM for MRP1 and 24.6+/-1.3 uM for MRP2 containing MDCKII cells. Cell proliferation analysis showed that the MDCKII control cells are very sensitive towards vincristine toxicity with an IC50 value of 1.1+/-0.1 uM. The MDCKII MRP1 and MRP2 cells are less sensitive towards vincristine toxicity with IC50 values of 33.1+/-1.9 and 22.2+/-1.4 uM, respectively. In both the MRP1 and MRP2 cells, exposure to 25 uM myricetin enhances the sensitivity of the cells towards vincristine toxicity to IC50 values of 7.6+/-0.5 and 5.8+/-0.5 uM, respectively. The increase of sensitivity represents a reversal of the resistance towards vincristine as a result of MRP1 and MRP2 inhibition...

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Non-Human Toxicity Values
LD50 Mouse intraperitoneal 1410 mg/kg

[1]. Semwal DK, et al. Myricetin: A Dietary Molecule with Diverse Biological Activities. Nutrients. 2016 Feb 16;8(2):90.
[2]. Phillips PA, et al. Myricetin induces pancreatic cancer cell death via the induction of apoptosis and inhibition of thephosphatidylinositol 3-kinase (PI3K) signaling pathway. Cancer Lett. 2011 Sep 28;308(2):181-8.
[3]. Xu Y, et al. Myricetin induces apoptosis via endoplasmic reticulum stress and DNA double-strand breaks in human ovarian cancer cells. Mol Med Rep. 2016 Mar;13(3):2094-100.
[4]. Jinwal UK, et al. Chemical Manipulation of Hsp70 ATPase Activity Regulates Tau Stability. J Neurosci. 2009 Sep 30;29(39):12079-88.
[5]. Tzeng SH, et al. Inhibition of platelet aggregation by some flavonoids. Thromb Res. 1991 Oct 1;64(1):91-100

Myricetin is a hexahydroxyflavone that is flavone substituted by hydroxy groups at positions 3, 3', 4', 5, 5' and 7. It has been isolated from the leaves of Myrica rubra and other plants. It has a role as a cyclooxygenase 1 inhibitor, an antineoplastic agent, an antioxidant, a plant metabolite, a food component, a hypoglycemic agent and a geroprotector. It is a hexahydroxyflavone and a 7-hydroxyflavonol. It is a conjugate acid of a myricetin(1-).
Myricetin has been reported in Caragana frutex, Camellia sinensis, and other organisms with data available.
Myricetin is a metabolite found in or produced by Saccharomyces cerevisiae.
See also: Quercetin (subclass of).

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Mechanism of Action
Dietary polyphenols are a diverse and complex group of compounds that are linked to human health. Many of their effects have been attributed to the ability to poison (i.e., enhance DNA cleavage by) topoisomerase II. Polyphenols act against the enzyme by at least two different mechanisms. Some compounds are traditional, redox-independent topoisomerase II poisons, interacting with the enzyme in a noncovalent manner. Conversely, others enhance DNA cleavage in a redox-dependent manner that requires covalent adduction to topoisomerase II. Unfortunately, the structural elements that dictate the mechanism by which polyphenols poison topoisomerase II have not been identified. To resolve this issue, the activities of two classes of polyphenols against human topoisomerase IIalpha were examined. The first class was a catechin series, including (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC). The second was a flavonol series, including myricetin, quercetin, and kaempferol. Compounds were categorized into four distinct groups: EGCG and EGC were redox-dependent topoisomerase II poisons, kaempferol and quercetin were traditional poisons, myricetin utilized both mechanisms, and ECG and EC displayed no significant activity. On the basis of these findings, a set of rules is proposed that predicts the mechanism of bioflavonoid action against topoisomerase II. The first rule centers on the B ring. While the C4'-OH is critical for the compound to act as a traditional poison, the addition of -OH groups at C3' and C5' increases the redox activity of the B ring and allows the compound to act as a redox-dependent poison. The second rule centers on the C ring. The structure of the C ring in the flavonols is aromatic and planar and includes a C4-keto group that allows the formation of a proposed pseudo ring with the C5-OH. Disruption of these elements abrogates enzyme binding and precludes the ability to function as a traditional topoisomerase II poison.
Selected flavonoids were tested for their ability to inhibit the catalytic activity of DNA topoisomerase (topo) I and II. Myricetin, quercetin, fisetin, and morin were found to inhibit both enzymes, while phloretin, kaempferol, and 4',6,7-trihydroxyisoflavone inhibited topo II without inhibiting topo I. Flavonoids demonstrating potent topo I and II inhibition required hydroxyl group substitution at the C-3, C-7, C-3', and C-4' positions and also required a keto group at C-4. Additional B-ring hydroxylation enhanced flavonoid topo I inhibitory action. A C-2, C-3 double bond was also required, but when the A ring is opened, the requirement for the double bond was eliminated. Genistein has been previously reported to stabilize the covalent topo II-DNA cleavage complex and thus function as a topo II poison. All flavonoids were tested for their ability to stabilize the cleavage complex between topo I or topo II and DNA. None of the agents stabilized the topo I-DNA cleavage complex, but prunetin, quercetin, kaempferol, and apigenin stabilized the topo II DNA-complex. Competition experiments have shown that genistein-induced topo II-mediated DNA cleavage can be inhibited by myricetin, suggesting that both types of inhibitors (antagonists and poisons) interact with the same functional domain of their target enzyme...
... myricetin (3, 3', 4', 5, 5', 7-hexahydroxyflavone) ... could directly bind to JAK1/STAT3 molecules to inhibit cell transformation in epidermal growth factor (EGF)-activated mouse JB6 P(+) cells. Colony assay revealed that myricetin had the strongest inhibitory effect on cell transformation among three flavonols including myricetin, quercetin and kaempferol. Molecular data revealed that myricetin inhibited DNA- binding and transcriptional activity of STAT3. Furthermore, myricetin inhibited the phosphorylation of STAT3 at Tyr705 and Ser727. Cellular signaling analyses revealed that EGF could induce the phosphorylation of Janus Kinase (JAK) 1, but not JAK2. Myricetin inhibited the phosphorylation of JAK1 and increased the autophosphorylation of EGF receptor (EGFR). Moreover, ex vivo and in vitro pull-down assay revealed that myricetin bound to JAK1 and STAT3, but not EGFR. Affinity data further demonstrated that myricetin had a higher affinity for JAK1 than STAT3. Thus, ... myricetin might directly target JAK1 to block cell transformation in mouse JB6 cells.
Abnormal expression of cyclooxygenase-2 (COX-2) has been implicated in the development of cancer. ... Here /it is reported/ that 3,3',4',5,5',7-hexahydroxyflavone (myricetin), one of the major flavonols in red wine, inhibits 12-O-tetradecanoylphorbol-13-acetate (phorbol ester)-induced COX-2 expression in JB6 P+ mouse epidermal (JB6 P+) cells by suppressing activation of nuclear factor kappa B (NF-kappaB). Myricetin at 10 and 20 uM inhibited phorbol ester-induced upregulation of COX-2 protein, while resveratrol at the same concentration did not exert significant effects. The phorbol ester-induced production of prostaglandin E 2 was also attenuated by myricetin treatment. Myricetin inhibited both COX-2 and NF-kappaB transactivation in phorbol ester-treated JB6 P+ cells, as determined using a luciferase assay. Myricetin blocked the phorbol ester-stimulated DNA binding activity of NF-kappaB, as determined using an electrophoretic mobility shift assay. Moreover, TPCK (N-tosyl-l-phenylalanine chloromethyl ketone), a NF-kappaB inhibitor, significantly attenuated COX-2 expression and NF-kappaB promoter activity in phorbol ester-treated JB6 P+ cells. In addition, red wine extract inhibited phorbol ester-induced COX-2 expression and NF-kappaB transactivation in JB6 P+ cells. Collectively, these data suggest that myricetin contributes to the chemopreventive effects of red wine through inhibition of COX-2 expression by blocking the activation of NF-kappaB.
For more Mechanism of Action (Complete) data for MYRICETIN (6 total), please visit the HSDB record page.

C15H10O8

318.24

318.037

C, 56.61; H, 3.17; O, 40.22

529-44-2

Dihydromyricetin;27200-12-0;Myricetin-13C3

5281672

Yellow needles from dilute alcohol

1.9±0.1 g/cm3

747.6±60.0 °C at 760 mmHg

>300 °C(lit.)

285.9±26.4 °C

0.0±2.6 mmHg at 25°C

1.864

2.11

6

8

1

23

506

0

O1C2=C([H])C(=C([H])C(=C2C(C(=C1C1C([H])=C(C(=C(C=1[H])O[H])O[H])O[H])O[H])=O)O[H])O[H]

IKMDFBPHZNJCSN-UHFFFAOYSA-N

InChI=1S/C15H10O8/c16-6-3-7(17)11-10(4-6)23-15(14(22)13(11)21)5-1-8(18)12(20)9(19)2-5/h1-4,16-20,22H

3,5,7-trihydroxy-2-(3,4,5-trihydroxyphenyl)chromen-4-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.08 mg/mL (6.54 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (6.54 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: 4% DMSO +30%PEG 300 +ddH2O: 5mg/mL

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 (Please use freshly prepared in vivo formulations for optimal results.)