• Korean Journal of Pharmacognosy
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• v.27 no.1
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• pp.75-79
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• 1996

Four steroids and one flavonol glycoside were isolated from the ethanol extract of the whole plant of Aconitum pseudolaeve var. erectum. Their structures were identified as ${\beta}-sitost-4-en-3-one$, 22-dihydro-stigmast-4-en-3,6-dione, ${\beta}-sitosterol$, ${\beta}-sitosterol-3-O-{\beta}-D-glucopyranoside$ and $kaempferol-3-O-{\beta}-D-glucopyranoside(astragalin)$ on the basis of spectral data.

• Journal of Microbiology and Biotechnology
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• v.30 no.1
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• pp.11-20
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• 2020

Quercetin and its derivatives are important metabolites that belong to the flavonol class of flavonoids. Quercetin and some of the conjugates have been approved by the FDA for human use. They are widely distributed among plants and have various biological activities, such as being anticancer, antiviral, and antioxidant. Hence, the biosynthesis of novel derivatives is an important field of research. Glycosylation and methylation are two important modification strategies that have long been used and have resulted in many novel metabolites that are not present in natural sources. A strategy for modifying quercetin in E. coli by means of glycosylation, for example, involves overexpressing respective glycosyltransferases (GTs) in the host and metabolic engineering for increasing nucleoside diphosphate sugar (NDP-sugar). Still others have used microorganisms other than E. coli, such as Streptomyces sp., for the biotransformation process. The overall study of the structural activity relationship has revealed that modification of some residues in quercetin decreased one activity but increased others. This review summarizes all of the information mentioned above.

• YAKHAK HOEJI
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• v.32 no.4
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• pp.281-286
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• 1988

For the investigation of medicinal resources in Hydrocotyle species, the studies were conducted to evaluate the pharmaco-constituents in Hydrocotyle japonica MAKINO (Umbelliferae), which is used as folk medicine in Korea. From the methyl alcohol extract of the whole plant, $isorhamnetin-3-O-{\beta}-D-galactoside$ ($C_{22}H_{22}O_{12}{\cdot}1/3H_2O$, bright yellow needle crystal, mp $247{\sim}248^{\circ}C$, $[{\alpha}]_D^{28}^{\circ}=-52.27^{\circ}$ in pyridine), one of three flavonol substances in extrat, was isolated and identified by physicochemical properties and spectroscopic evidences (UV, IR, NMR and MS etc.,) in comparison with authentic sample. This flavonoid was appeared from Hydrocotyle japonica MAKINO through phytochemical approaches at the outset.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.11a
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• pp.66-66
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• 2003

Flavonoids are phenolic compounds widely distributed in wide variety of edible plants including leafy vegetables, fruits, beverages. Quercetin is one of bioflavonoid compounds and has anti-tumor effect by suppressing tumor growth in vitro and in vivo, including multiple biological effects by antioxidant and effective anti-inflammatory agent. The present study investigated whether quercetin can enhance antioxidant enzyme activities (glutathione peroxidase: GPX, superoxide dismutase : SOD, catalase: CAT) and intracellular reactive oxygen intermediate (ROI) levels in the presence of taurine on B16F10 murine melanoma cells. From this result, the antioxidant enzyme activities of quercetin in the presence of taurine was enhanced. In addition, the same treatments decreased intracellular reactive oxygen intermediate levels on B16F10 murine melanoma cells. Taken together, these results demonstrate that the antioxidant effect of quercetin can enhance in the presence of taurine and it might play an important role in anti-tumor effect.

• Molecules and Cells
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• v.25 no.2
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• pp.312-316
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• 2008

Flavanone $3{\beta}$-hydroxylases (F3H) are key enzymes in the synthesis of flavonol and anthocyanin. In this study, three F3H cDNAs from Oryza sativa (OsF3H-1 ~3) were cloned by RT-PCR and expressed in E. coli as gluthatione S-transferase (GST) fusion proteins. The purified recombinant OsF3Hs used flavanone, naringenin and eriodictyol as substrates. The reaction products with naringen and eriodictyol were determined by nuclear magnetic resonance spectroscopy to be dihydrokaempferol and taxifolin, respectively. OsF3H-1 had the highest enzymatic activity whereas the overall expression of OsF3H-2 was highest in all tissues except seeds. Flavanone $3{\beta}$-hydroxylase could be a useful target for flavonoid metabolic engineering in rice.

• Natural Product Sciences
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• v.12 no.3
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• pp.122-124
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• 2006

Three flavonoid glycosides, $kaempferol-3-O-{\alpha}-L-rhamnopyranosyl-(1\;{\rightarrow}\;6)-{\beta}$-D-glucopyranoside$ or kaempferol-3-O-rutinoside (1), $isorhamnetic-3-O-{\alpha}-L-rhamnopyranosyl-(16)-{\beta}-D-glucopyranoside$ or isorhamnetin-3-O-rutinoside (2), and $quercetin-3-O-{\beta}-D-glucopyranosyl-(1 ${\rightarrow}\;2)-{\beta}-L-arabinopyranoside$ 3, the latter one being a new compound, were isolated from the methanolic extract of the aerial parts of Carrichtera annua. Mass spectrometry and 1D and 2D NMR spectroscopy allowed establishing the structure of these compounds.

• YAKHAK HOEJI
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• v.38 no.4
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• pp.469-475
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• 1994

As the continued studies for Korean cultivated rhubarb, MeOH extract of the leaves was fractionated with ether, ethylacetate, and n-butanol. From the ethyl acetate fraction of MeOH extract, one flavone glycoside, apigenin-8-${\beta}$-D-glucopyranoside(vitexin, $C_{21}H_{20}O_{10}$) and from the n-BuOH fraction of MeOH extract, two flavonol glycosids, kaempferol-3-O-(2,6-di-O-rhamnopyranosyl)-${\beta}$-D-galactopyranoside$(C_{33}H_{40}O_{19})$and quercetin-3-O-rutinoside(rutin, $C_{27}H_{30}O_{16}$) were isolated and identified through the physico-chemical properties and spectroscopic evidences(UV, IR, NMR, Mass) respectively.

• YAKHAK HOEJI
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• v.36 no.3
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• pp.205-211
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• 1992

A simple dignostic method using Fast Atom Bombardment mass spectrometry was applied to the characterization of green tea flavonols from the eluates of Sepahadex LH-20 column chromatography. From the ethyl acetate extracts, crude mixture of flavonol fraction(Fr.$1{\sim}4$) were separated by the stepwise gradient elution with 30, 45, and 60% aqueous acetone. Procyanidine B analogues were found to be typical constituents of Fr. 1. Main components of Fr. 2 were catechins and gallo-catechins. Fr. 3 contained mainly ester type compounds, catechin-gallates, gallocatechin-gallates with their analogues. Fr. 4 was contaminated with some phthalate esters.

• Archives of Pharmacal Research
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• v.29 no.3
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• pp.199-202
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• 2006

From the leaves of Goniothalamus tenuifolius, a new natural product namely 3'-hydroxy-3,5,7,4'-tetramethoxyflavone (1) was isolated, along with seven other known compounds (2-8). Each of these isolates was evaluated for free radical scavenging activity on the DPPH decoloration test. The data obtained in this study suggested that the ortho 3',4'-diphenolic structure was essential for the activity of these flavonol derivatives.

• Korean Journal of Pharmacognosy
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• v.26 no.1
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• pp.23-26
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• 1995

6-Hydroxykynurenic acid and ginkgolide B together with flavonol glycosides and biflavonoids were isolated from the yellow leaves of Ginkgo biloba and identified by means of spectroscopic methods. The correctness of $H{\"{o}}lzl's$ ${13}^C-NMR$ assignments for 6-hydroxykynurenic acid was confirmed by HMQC and HMBC techniques. Based on our present findings, it may be considered that the yellow Ginkgo leaves may contribute to be a source of high medicinal values.