• Journal of Microbiology and Biotechnology
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• v.21 no.8
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• pp.854-857
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• 2011

POMT7, which is an O-methyltransferase from poplar, transfers a methyl group to several flavonoids that contain a 7-hydroxyl group. POMT7 has been shown to have a higher affinity toward quercetin, and the reaction product rhamnetin has been shown to inhibit the formation of beta-amyloid. Thus, rhamnetin holds great promise for use in therapeutic applications; however, methods for mass production of this compound are not currently available. In this study, quercetin was biotransformed into rhamnetin using Escherichia coli expressing POMT7, with the goal of developing an approach for mass production of rhamnetin. In order to maximize the production of rhamnetin, POMT7 was subcloned into four different E. coli expression vectors, each of which was maintained in E. coli with a different copy number, and the best expression vector was selected. In addition, the S-adenosylmethionine biosynthesis pathway was engineered for optimal cofactor production. Through the combination of optimized POMT7 expression and cofactor production, the production of rhamnetin was increased up to 111 mg/l, which is approximately 2-fold higher compared with the E. coli strain containing only POMT7.

• Nutrition Research and Practice
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• v.9 no.6
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• pp.586-591
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• 2015

BACKGROUND/OBJECTIVES: Reactive oxygen species (ROS) formation is closely related to miconazole-induced heart dysfunction. Although rhamnetin has antioxidant effects, it remained unknown whether it can protect against miconazole-induced cardiomyocyte apoptosis. Thus, we investigated the effects of rhamnetin on miconazole-stimulated H9c2 cell apoptosis. MATERIALS/METHODS: Cell morphology was observed by inverted microscope and cell viability was determined using a WelCount$^{TM}$ cell proliferation assay kit. Miconazole-induced ROS production was evaluated by fluorescence-activated cell sorting with 6-carboxy-2',7'-dichlorofluoroscein diacetate ($H_2DCF$-DA) stain. Immunoblot analysis was used to determine apurinic/apyrimidinic endonuclease 1 (APE/Ref-1) and cleaved cysteine-aspartic protease (caspase) 3 expression. NADPH oxidase levels were measured using real-time polymerase chain reaction. RESULTS: Miconazole (3 and $10{\mu}M$) induced abnormal morphological changes and cell death in H9c2 cells. Rhamnetin enhanced the viability of miconazole ($3{\mu}M$)-treated cells in a dose-dependent manner. Rhamnetin (1 and $3{\mu}M$) treatment downregulated cleaved caspase 3 and upregulated APE/Ref-1 expression in miconazole-stimulated cells. Additionally, rhamnetin significantly reduced ROS generation. CONCLUSIONS: Our data suggest that rhamnetin may have cytoprotective effects in miconazole-stimulated H9c2 cardiomyocytes via ROS inhibition. This effect most likely occurs through the upregulation of APE/Ref-1 and attenuation of hydrogen peroxide levels.

• Korean Journal of Pharmacognosy
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• v.29 no.3
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• pp.163-168
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• 1998

Seven antioxidative compounds were isolated from chloroform and ethyl acetate extracts of the stem bark of Eucalyptus globulus (Myrtaceae). They were identified as rhamnazin (1), rhamnetin (2), naringenin (3), eriodictyol (4), quercetin (5), taxifolin (6) and dihydrokaempferol-3-rhamnoside (7) on the basis of various spectroscopic analyses. These compounds inhibited lipid peroxidation with $IC_{50}$ values of 0.08-30 ${\mu}g/ml$.

• Natural Product Sciences
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• v.4 no.4
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• pp.221-225
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• 1998

A novel flavonol trisulphate, quercetin 7-methyl ether $3,3',4'-tri-O-KSO_3$ was isolated from the fresh leaves of Tamarix amplexicaulis (Tamaricaceae) along with the known flavonol mono sulphates, quercetin $3-O-KSO_3$ and quercetin 4'-methyl ether $3-O-KSO_3$. Structures were achieved through conventional analytical methods, including electrophoretic analysis and confirmed by FAB-MS and NMR spectroscopy.

• Journal of Applied Biological Chemistry
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• v.52 no.1
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• pp.15-20
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• 2009

Poplar contains various flavonoids including naringenin, kaempferol, myricetin, apigenin, luteolin, rhamnetin, and quercetin. These flavonoids are synthesized from naringenin with various enzymes. However, none of genes from poplar involved in flavonoid biosynthesis have been biochemically characterized. We cloned PFNS I-1 from Populus deltoids by RT-PCR method. The open reading frame of PFNS I-1 consisted of 1,017-bp and it showed high similarity with other FNS genes. The purified recombinant PFNS I-1, expressed in Escherichia coli, catalyzed the reaction from flavanone (naringenin) to flavone (apigenin). The reaction of PFNS I-1 was enhanced by cofactors such as oxoglutarate, $Fe^{2+}$, ascorbate and catalase. Thus, it is concluded that PFNS N-1 encodes a flavone synthase I.

• Journal of Plant Biotechnology
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• v.46 no.4
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• pp.338-345
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• 2019

The selection of a suitable solvent is very important when preparing an extract. However, the effect of ethanol solvent concentration in the extraction of sweet wormwood tea has not been reported. Thus, extracts were prepared from sweet wormwood tea using water and various ethanol concentrations, and the phenolic compounds, antioxidants and anti-enzyme activities of the extracts were analyzed. The phenolic acid and flavonoid components differed according to extraction solvent, which also resulted in different antioxidant and antienzyme activities. In particular, flavonoid rhamnetin was not extracted using 80% and 99.5% ethanol and was highest when 60% ethanol was used for extraction. In the case of chlorogenic acid, the highest extraction efficiency was obtained with 80% ethanol. These results suggest the need for research to increase specific extraction efficiency by targeting major compounds that affect physiological activity.

• BMB Reports
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• v.42 no.1
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• pp.41-46
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• 2009

Post-transcriptional regulation of mRNA stability by Hu proteins is an important mechanism for tumorigenesis. We focused on the molecular interactions between the HuC protein and AU-rich elements (AREs) to find chemical inhibitors of RNA-protein interactions using RNA electrophoretic mobility shift assay with non-radioactive probes. Screening of 52 natural compounds identified 14 candidate compounds that displayed potent inhibitory activity. Six (quercetin, myricetin, (-)-epigallocatechin gallate, ellagic acid, (-)-epicatechin gallate, and rhamnetin) were categorized as phytochemicals, and their $IC_{50}$ values were low ($0.2-1.8\;{\mu}M$).

• Korean Journal of Plant Resources
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• v.30 no.6
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• pp.618-622
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• 2017

Various bioactive substances are found in Loranthus tanakae, including quercetin 3-rhamnoside (1), kaempferol 3-rhamnoside (2), rhamnetin 3-rhamnoside (3), and rhamnocitrin 3-rhamnoside (4), which inhibit tyrosinase. These compounds are mainly found in the EtOAc fraction of L. tanakae extract and demonstrate higher rates of tyrosinase inhibition than ascorbic acid, which was used as a control. Our results suggest that L. tanakae extracts can be utilized in skin whitening cosmetics.

• Archives of Pharmacal Research
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• v.23 no.2
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• pp.147-150
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• 2000

Twelve compounds with lipid peroxidation inhibitory activity were isolated from the stem bark of E. globulus. Their structures were assigned as a new aromatic monoterpene (1) and eleven known compounds, pinoresinol (2), vomifoliol (3), 3,4,5-trimethoxyphenol 1-O-$\beta$-D-(6'-O-galloyl)glucopyranoside (4), methyl gallate (5), rhamnazin (6), rhamnetin (7), eriodictyol (8), quercetin (9), taxifolin (10), engelitin (11), and catechin (12) on the basis of UV, mass, and NMR spectroscopic analyses. These compounds except vomifoliol significantly inhibited lipid peroxidation in rat liver microsome.

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2147-2150
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• 2010

c-Jun N-terminal kinase 1 (JNK1) is involved in apoptosis, cell differentiation and proliferation. It has been reported that a flavonol, quercetin, induces cell apoptosis and JNK inhibition. In order to understand the interactions of quercetin and JNK1, we performed receptor-oriented pharmacophore based in silico screening and determined a binding model of human JNK1 and quercetin at the ATP binding site of JNK1. 5-OH of A-ring and carbonyl oxygen of C-ring of quercetin participated in hydrogen bonding interactions with backbone of E109 and M111. Additionally, 3'-OH of quercetin formed a hydrogen bond with backbone of I32. One hydrophobic interaction is related on the binding of quercetin to JNK1 with I32, N114, and V158. Based on this model, we conducted a docking study with other 8 flavonols to find possible flavonoids inhibitors of JNK1. We proposed that one flavonols, rhamnetin, can be a potent inhibitor of JNK and 5-OH of A-ring and 3'-OH of B-ring of flavonols are the essential features for JNK1 inhibition.