Aromatase; Synthetic and natural flavonoid

The effect of α-naphthoflavone (α-NF) on vascular function was studied in isolated ring segments of the rat thoracic aorta and in primary cultures of human umbilical vein endothelial cells (HUVECs). α-NF induced concentration-dependent relaxation of the phenylephrine-precontracted aorta endothelium-dependently and -independently at lower and higher concentrations, respectively. The cGMP, but not cAMP, content was increased significantly in α-NF-treated aorta. Pretreatment with N ω-nitro-L-arginine methyl ester (L-NAME) or methylene blue attenuated both α-NF induced vasorelaxation and the increase of cGMP content significantly. The increase of cGMP content induced by α-NF was also inhibited by chelating extracellular Ca2+ with EGTA. These results suggest that the endothelium-dependent vasorelaxation induced by α-NF is mediated most probably through Ca2+-dependent activation of NO synthase and guanylyl cyclase. In HUVECs, α-NF induced concentration-dependent formation of NO and Ca2+ influx. α-NF-induced NO formation was abolished by removal of extracellular Ca2+ and by pretreatment with the Ca2+ channel blockers SKF 96365 and Ni2+, but not by the L-type Ca2+ channel blocker verapamil. The Ca2+ influx, as measured by 45Ca2+ uptake, induced by α-NF was also inhibited by SKF 96365 and Ni2+. Our data imply that α-NF, at lower concentrations, induces endothelium-dependent vasorelaxation by promoting extracellular Ca2+ influx in endothelium and the activation of the NO-cGMP pathway[2].

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease. The literature suggests that the aryl hydrocarbon receptor (AHR) may be a key player in the pathogenesis of NAFLD, and it can modulate the synthesis of cytochrome P450 1A1 (CYP1A1) and tumor necrosis factor-α (TNF-α). Previous studies have shown that CYP1A1 is a key enzyme of oxidative stress, TNF-α is involved in the formation of insulin resistance (IR), oxidative stress and insulin resistance are the key factors for the formation of NAFLD. Therefore, it can be said that AHR may participate in contributing to NAFLD by regulating CYP1A1 and TNF-α. Alpha-naphthoflavone (ANF) is an effective AHR inhibitor. The present study was designed to explore the hepatoprotective effect of ANF in high fat diet (HFD)-induced NAFLD mice and oleic acid (OA)-treated HepG2 hepatocytes. Mice were fed HFD to induce NAFLD, HepG2 cells were exposed to OA to induce hepatocyte injury, and ANF significantly reduced mouse and cellular liver damage compared to the HFD-induced NAFLD and OA-treated HepG2 hepatocytes. ANF treatment reduces liver damage by reducing ROS and IR, the data show that ANF inhibits the expression of AHR, CYP1A1 and TNF-α in NAFLD. Taken together, these findings show that ANF alleviate NAFLD via regulation of AHR/CYP1A1 and AHR/TNF-α pathways, which may have potential for further development as novel therapeutic agents for NAFLD[4].

Biochemical analysis[4]
According to the manufacturer's instructions. Detection of aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride (TG) and total cholesterol (TC), catalase (CAT), glutathione (GSH), malondialdehyde (MDA) and superoxide dismutase (SOD) enzyme activity using a commercial assay kit.

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Eleven flavonoid compounds were compared with aminoglutethimide (AG), a pharmaceutical aromatase inhibitor, for their abilities to inhibit aromatase enzyme activity in a human preadipocyte cell culture system. Flavonoids exerting no effect on aromatase activity were catechin, daidzein, equol, genistein, beta-naphthoflavone (BNF), quercetin and rutin. The synthetic flavonoid, alpha-naphthoflavone (ANF), was the most potent aromatase inhibitor, with an I50 value of 0.5 microM. Three naturally-occurring flavonoids, chrysin, flavone, and genistein 4'-methyl ether (Biochanin A) showed I50 values of 4.6, 68, and 113 microM, respectively, while AG showed an I50 value of 7.4 microM. Kinetic analyses showed that both AG and the flavonoids acted as competitive inhibitors of aromatase. The Ki values, indicating the effectiveness of inhibition, were 0.2, 2.4, 2.4, 22, and 49 microM, for ANF, AG, chrysin, flavone, and Biochanin A, respectively. Chrysin, the most potent of the naturally-occurring flavonoids, was similar in potency and effectiveness to AG, a pharmaceutical aromatase inhibitor used clinically in cases of estrogen-dependent carcinoma. These data suggest that flavonoid inhibition of peripheral aromatase activity may contribute to the observed cancer-preventive hormonal effects of plant-based diets[1].

Cell culture and cell treatment[4]
Human hepatocellular carcinoma cell line HepG2 (ATCC, US) was cultured in DMEM medium supplemented with 10% fetal bovine serum (FBS) and 1% penicillin-streptomycin solution. The culture was maintained at 37 °C in a humidified 5% CO2 incubator. To induce excessive lipid accumulation in an in vitro hepatic steatosis model, The cells were divided into 6 groups: (1) control group (C), (2) model control group (M), (3) model control group containing α-Naphthoflavone/ANF (5 μM) (ANF5) (5), (4) model control group ANF (10 μM) (ANF10), (5) model control group containing ANF (20 μM), (6) model control group containing ANF (40 μM) (ANF40), except for the control group, the remaining groups of cells were exposed in medium, and the medium was supplemented with 0.1 mM oleic acid for 48 h. ANF was dissolved in dimethyl sulfoxide (DMSO) and cells were incubated with different concentrations of ANF (0/5/10/20/40 μM) during the last 24 h of the 48 h treatment.

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MTT assay[4]
HepG2 cells (1 × 104cells/mL) were seeded in 96-well plates, and inhibition experiments were carried out in the presence of 5 μM, 10 μM, 20 μM, 40 μM α-Naphthoflavone/ANF and 0.1 mM oleic acid. Cells were incubated in the incubator for 48 h before detection.

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Human papilloma viruses 16 and 18 express E6 and E7 oncoproteins. E6 activates and redirects E6-associated protein (E6AP), an E3 ubiquitin ligase. E6AP interacts with Ube2l3, an E2 ubiquitin conjugating enzyme protein (also known as UbcH7), to promote p53 ubiquitination and degradation by the 26S proteasome. Therefore, blocking E6-mediated p53 degradation might be an alternative treatment for cervical cancer. In addition, activation of the aryl hydrocarbon receptor (AHR) induces Ube2l3 expression, resulting in p53 ubiquitination and degradation. The aim of the present study was to determine whether inhibition of AHR in HeLa cells resulted in an increase in p53 and apoptosis along with a decrease in cell proliferation. The results demonstrate that two AHR antagonists, α-naphthoflavone (α-NF) and resveratrol, decreased cell proliferation, arrested cells in the gap 1/synthesis (G1/S) phases, and increased p53 levels and apoptosis. However, knocking out the Ahr gene did not abrogate the effects of α-NF and resveratrol. Moreover, Ahr-null cells presented similar cell proliferation rates and apoptosis levels when compared to control HeLa cells. Taken together, the results indicate that α-NF's and resveratrol's cytostatic and cytotoxic actions, respectively, occur through an AHR-independent mechanism, and that AHR is not required for HeLa cell proliferation[3].

Male C57 mice (18–20 g, 6–8 weeks) were housed in plastic cages, casual food and water, and maintained at room temperature (25 ± 2 °C) under a 12 h light/dark cycle. After one week of adaptation, animals were randomized into 4 groups (6 in each group): (1) normal control group (C), (2) high-fat diet control group (M), (3) high-fat diet containing 80 mg/kg/day α-Naphthoflavone/ANF (ANF80), (4) high-fat diet containing 160 mg/kg/day ANF (ANF160). Control mice were fed a normal diet (fat 10% calories, protein 20% calories, carbohydrate 70% calories; 3.5 Kcal/g diet), and the other 3 groups of mice fed a high-fat diet (fat 42% calories), protein 15% calories, carbohydrate calories 43%; diet 4.5 Kcal/g). The total feeding duration is 12 weeks. The normal control group was fed a normal diet and the remaining 3 groups were fed a high-fat diet. Three groups of mice fed high-fat diets were given different ANF doses (0, 80, 160 mg/kg/day) by gavage in the last four weeks of feeding. After 12 weeks, the mice were euthanized and tissue samples and blood were collected for further analysis.[4]

[1]. Flavonoid inhibition of aromatase enzyme activity in human preadipocytes. J Steroid Biochem Mol Biol. 1993 Sep;46(3):381-8.

[2]. Alpha-naphthoflavone induces vasorelaxation through the induction of extracellular calcium influx and NO formation in endothelium. Naunyn Schmiedebergs Arch Pharmacol. 2003 Nov;368(5):377-85.

[3]. Apoptosis induction and inhibition of HeLa cell proliferation by alpha-naphthoflavone and resveratrol are aryl hydrocarbon receptor-independent. Chem Biol Interact. 2018 Feb 1;281:98-105.

[4]. Alpha-naphthoflavone attenuates non-alcoholic fatty liver disease in oleic acid-treated HepG2 hepatocytes and in high fat diet-fed mice. Biomed Pharmacother. 2019 Oct;118:109287.

Alpha-naphthoflavone is an extended flavonoid resulting from the formal fusion of a benzene ring with the h side of flavone. A synthetic compound, it is an inhibitor of aromatase (EC 1.14.14.14). It has a role as an EC 1.14.14.14 (aromatase) inhibitor, an aryl hydrocarbon receptor antagonist and an aryl hydrocarbon receptor agonist. It is an organic heterotricyclic compound, an extended flavonoid and a naphtho-gamma-pyrone.
alpha-Naphthoflavone has been reported in Rhaponticum repens with data available.

C19H12O2

272.2974

272.083

604-59-1

11790

White to light yellow solid powder

1.3±0.1 g/cm3

460.9±45.0 °C at 760 mmHg

153-157 °C(lit.)

215.8±22.3 °C

0.0±1.1 mmHg at 25°C

1.695

4.79

0

2

1

21

433

0

VFMMPHCGEFXGIP-UHFFFAOYSA-N

InChI=1S/C19H12O2/c20-17-12-18(14-7-2-1-3-8-14)21-19-15-9-5-4-6-13(15)10-11-16(17)19/h1-12H

2-phenylbenzo[h]chromen-4-one

alpha-Naphthoflavone; 7,8-Benzoflavone; 604-59-1; 2-Phenyl-4H-benzo[h]chromen-4-one; alpha-Naphthylflavone; 2-phenylbenzo[h]chromen-4-one; Benzo(h)flavone; 4H-Naphtho[1,2-b]pyran-4-one, 2-phenyl-;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

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

DMSO : ~25 mg/mL (~91.81 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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