• Journal of Microbiology and Biotechnology
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• 제21권8호
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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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• 제9권6호
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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.

• 생약학회지
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• 제29권3호
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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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• 제4권4호
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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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• 제52권1호
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• pp.15-20
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• 2009

포플러는 naringenin, kaempferol, myricetin, apigenin, luteolin, rhamnetin, quercetin과 같은 플라보노이드를 가지고 있다. 이러한 플라보노이드들은 여러 가지 효소에 의해 naringenin으로부터 합성된다. 그러나, 포플러에서는 플라보노이드 합성에 관여하는 효소들의 연구가 거의 이루어지지 않았다. 포플러에서 flavone synthase I 유전자를 RT-PCR방법을 이용하여 클로닝하였다. PFNS I-1 유전자의 기질 특성을 알아보기 위하여 대장균에 과발현하여 glutathione S-transferase 친화 크로마토그래피를 이용하여 정제하였다. 정제한 PFNS I-1 재조합 단백질은 flavanone인 2S-naringenin기질을 이용하여 flavone인 apigenin을 생성함을 알 수 있었다. 또한 cofactor인 oxoglutarate, $FeSO_4$, ascorbate, catalase가 PFNS I-1의 반응성에 중대한 영향을 미치는 것을 알 수 있었다. 이상의 결과를 종합해 볼 때 PFNS I-1 유전자는 flavone synthase I을 암호화하는 유전자임을 확인하였다.

• Journal of Plant Biotechnology
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• 제46권4호
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• pp.338-345
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• 2019

본 연구에서는 개똥쑥 차를 이용한 가공식품 및 천연소재를 개발하고자 물과 다양한 농도의 에탄올로 추출하여 페놀 및 플라보노이드 성분을 분석하였고 항산화 및 항효소 활성을 비교하였다. 개똥쑥 차 추출물은 용매에 따라 총 페놀과 플라보노이드 함량에 유의적인 차이를 보였고 이를 통해 추출요인으로서 에탄올 농도가 중요한 역할을 하는 것으로 확인되었다. 또한 HPLC로 분석된 페놀산과 플라보노이드 정량분석 결과 구성 성분의 차이가 있었으며 이에 따라 항산화 및 항효소 활성에도 영향을 주었다. 개똥쑥 차 이용 측면에서 에탄올 농도 조절을 통해 목적에 맞는 용매 선택을 제안하는 바이다.

• BMB Reports
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• 제42권1호
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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 ($0.2-1.8\;{\mu}M$).

• 한국자원식물학회지
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• 제30권6호
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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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• 제23권2호
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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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• 제31권8호
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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.