• YAKHAK HOEJI
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• v.37 no.4
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• pp.325-330
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• 1993

Four flavonoide glycosides and (-)-Epicatechin were isolated from the aqueous extracts of dried whole part of Lysimachia clethroides Duby(Primulaceae). They were 3-0-Methyl-quercetin-7-0-[$\alpha$-L- rhamnopyranosyl (1-2) glucopyranoside], Quercetin-3-0-$\beta$-D-glucopyranoside, Kaempferol-3-0-$\beta$-D-glucopyranoside, Kaempferol-3-0-[$\alpha$-L-rhamnopyranosyl (1-6)-$\beta$-D-glucopyranoside] and (-)-Epicatechin. 3-0-[$\alpha$-L-rhamnopyranosyl (1-6)-$\beta$-D-glucopyranoside]and (-)-Epicatechin. 3-0-Methyl-quercetin-7-0-[$\alpha$-L-rhamnopyranosyl (1-2)-$\beta$-D-glucopyranoside] and (-)-Epicatechin were first isolated from this plant. Their structures were elucidated by spectral analysis [$^{1}$H-, $^{13}C-$ NMR, $^{1}$H-$^{1}$H-COSY, DEPT-analysis, HMQC(Heteronuclear multiple quantum coherence), FAB-MS].

• Korean Journal of Pharmacognosy
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• v.35 no.2 s.137
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• pp.139-142
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• 2004

One anthraquinone and four flavonoids were isolated from the extract of leaves and twigs of Rhamnus taquetii. By physicochemical and spectral methods, their structures were identified as physcion (1), keampferol (2), rhamnocitrin (3), quercetin (4), and 3-O-methyl quercetin (5).

• Natural Product Sciences
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• v.6 no.3
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• pp.135-138
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• 2000

MeOH extract of Cuscuta chinensis seeds was fractionated with n-hexane, EtOAc and BuOH successively, and antioxidant activities were tested for all fractions using DPPH free radical scavenging method. In the tested fractions, EtOAc fraction showed high antioxidant activity$(EC_{50},\;50\;{\mu}g)$ From the EtOAc fraction, five compounds have been isolated. On the basis of spectral data, these compounds were identified as ${\beta}-sitosterol$, methyl 4-hydroxy-3,5-dimethoxycinnamate, ${\beta}-sitosterol-3-O-{\beta}-D-glucopyranoside$, caffeic acid, quercetin, kaempferol and calycopteretin. Among these compounds, ${\beta}-sitosterol$ and ${\beta}-sitosterol-3-O-{\beta}-D-glucopyranoside$ showed no antioxidant activity. $EC_{50}$ values of methyl 4-hydroxy-3,5-dimethoxycinnamate, caffeic acid, quercetin, kaempferol and calycopteretin were 0.6, 8, 19, 17 and $12\;{\mu}g$, respectively.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.5
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• pp.361-365
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• 2009

Effects of quercetin, a kind of flavonoids, on the vasodilating actions were investigated. Among the mechanisms for quercetin-induced vasodilatation in rat aorta, the involvement with the $Ca^{2+}$ activated $K^+$ ($K_{Ca}$) channel was examined. Pretreatment with NE ($5\;{\mu}M$) or KCl (60 mM) was carried out and then, the modulation by quercetin of the constriction was examined using rat aorta ring strips (3 mm) at $36.5^{\circ}C$. Quercetin (0.1 to $100\;{\mu}M$) relaxed the NE-induced vasoconstrictions in a concentrationdependent manner. NO synthesis (NOS) inhibitor, NG-monomethyl-L-arginine acetate (L-NMMA), at $100\;{\mu}M$ reduced the quercetin ($100\;{\mu}M$)-induced vasodilatation from $97.8{\pm}3.7%$ (n=10) to $78.0{\pm}11.6%$ (n=5, p<0.05). Another NOS inhibitor, L-NG-nitro arginine methyl ester (L-NAME), at $10\;{\mu}M$ also had the similar effect. In the presence of both $100\;{\mu}M$ L-NMMA and $10\;{\mu}M$ indomethacin, the quercetin-induced vasodilatation was further attenuated by $100\;{\mu}M$ tetraethylammonium (TEA, a $K_{Ca}$ channel inhibitor). Also TEA decreased the quercetin-induced vasodilatation in endothelium-denuded rat aorta. Used other $K_{Ca}$ channel inhibitors, the quercetin-induced vasodilatation was attenuated by $0.3\;{\mu}M$ apamin (a SK channel inhibitor), but not by 30 nM charybdotoxin (a BK and IK channel inhibitor). Quercetin caused a concentration-dependent vasodilatation, due to the endotheliumdependent and -independent actions. Also quercetin contributes to the vasodilatation selectively with SK channel on smooth muscle.

• YAKHAK HOEJI
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• v.45 no.3
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• pp.237-244
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• 2001

The herbaceous species of phyllanthus in this genus are used as hyperglycemic, diuretic, and malaria agent in the world. For the phytochemical studies and the investigation of medicinal resources in the Phyllanthus species, Phyllanthus ussuriensis (Euphorbiaceae) were used and the studies of constituents in this plant were carried out. From the aqueous fraction of methanolic extract, one flavonoid (quercetin-3-O-rutinoside), two gallotannins (gallic acid, methyl gallate), and two ellagitannins (corilagin, geraniin) were isolated through fractionation and repeated column chromatography using Amberlite XAD-4, ODS gel, and sephadex LH-20. The structures of these compounds were identified on the basis of spectroscopic evidences.

• Archives of Pharmacal Research
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• v.27 no.3
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• pp.300-304
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• 2004

Five caffeic acid derivatives; methyl ester of caffeoylglycolic acid (1), dimethyl ester of caffeoyltartaric acid (2), dimethyl ester of caffeoyltartronic acid (3), monomethyl ester of caffeoyltartronic acid (4), methyl ester of caffeic acid (5), and some other secondary metabolites including; quercetin, quercetin 3-O-$\beta$-D-glucuronide methyl ester, kaempferol, 3,5,7,4'-O-tetramethylkaempferol, $\beta$-sitosterol glucoside, 2$\alpha$-hydroxyursolic acid and 2,24-dihydroxyursolic acid, have been isolated and characterized. All the isolated compounds were characterized with the help of NMR spectroscopy and mass spectrometry. Structure of compound 3 was also confirmed by a single X-ray crystallographic technique. Isolates were evaluated for anti-oxidant activities and most of the tested compounds were found to be potent in DPPH free radical scavenging ($IC_{50}{\;}={\;}4.56-14.17{\;}{\mu\textrm{g}}/mL$) and superoxide anion scavenging ($IC_{50}{\;}={\;}0.58-7.39{\;}{\mu\textrm{g}}/mL$) assays.

• Archives of Pharmacal Research
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• v.26 no.7
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• pp.535-539
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• 2003

The EtOAc soluble fraction from the stem of Sorghum bicolor showed a strong free radical scavenging activity. Five major compounds were isolated from this fraction. They were identified by spectral data as methyl ferulate (1), methyl p-hydroxycinnamate (2), p-hydroxybenzaldehyde (3), tricin (4), and quercetin 3,4 -dimethyl ether (5). Among these compounds, 1 exhibited a strong, free radical scavenging activity on 1, 1-diphenyl-2-picrylhydrazyl (DPPH) with an $IC_50$ value of 0.7 $\mu$M. We further studied the effects of these isolated compounds on the lipid peroxidation in rat liver microsomes induced by non-enzymatic method. All five compounds showed anti-lipid peroxidation activity ($IC_50$ values of 0.5, 0.4, 0.3 and 0.3 $\mu$ M, respectively).

• Microbiology and Biotechnology Letters
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• v.38 no.3
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• pp.278-282
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• 2010

In this study, the antibacterial activity and component analysis of Persicaria perfoliata extracts were investigated. MIC (Minimum Inhibitory Concentration) values of ethyl acetate fraction from P. perfoliata on Escherichia coli, Propionibacterium acnes, and Staphylococcus aureus were 0.25%, equally. The results showed that the antibacterial activity of the ethyl acetate fraction was the highest in the S. aureus and P. acnes. Ethyl acetate fraction from P. perfoliata extracts showed 5 bands in TLC and 8 peaks in HPLC (320nm). In HPLC chromatogram of ethyl acetate fraction, first main peak 2 (24.99%) and peak 3 (22.65%) were identified as quercetin-3-o-glucuronide and isoquercitrin in the order of elution time. Also, in HPLC chromatogram of deglycosylated fraction, main peak 2 (76.93%) was identified as quercetin in the order of elution time. And these components are very effective as antioxidants. Thus, these results indicate that extract/fractions of P. perfoliata can be applicable to new functional cosmetics for antioxidant, antibacterial activity.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.2
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• pp.162-166
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• 2005

Two flavonoids, 7-O-methyl-3',4'-didehydroxy quercetin (MDQ) and quercetin, isolated from Chinese propolis, which is the generic name for the resinous substance collected by honeybees from various plant sources, were tested for their antioxidant activity and protective effect against radiation-induced DNA damage in mouse lymphocytes. In antioxidant test, both compounds provided a dose-dependent scavenging effect on DPPH radical and a dose-dependent inhibitory effect on lipid peroxidation in mouse liver. Quercetin showed stronger scavenging and inhibitory effect than MDQ, and it also provided strong inhibition on superoxide anion radical generated in xanthine-xanthine oxidase system, but there was no inhibitory ability for MDQ. In comet assay using single cell gel electrophoresis, MDQ and quercetin showed a protective effect against DNA damage caused by gamma irradiation. They reduced DNA damage to 54% (p<0.01) and 53% (p<0.01) at 25 $\mu$mol, respectively. These results suggest that free radical scavenging seems to be associated with their catechol form on the B ring, and radioprotection appears to be a likely mechanism of antioxidant activity by these flavonoids.

• Korean Journal of Pharmacognosy
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• v.37 no.3
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• pp.162-168
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• 2006

The isolation and identification of a new xanthone (6-0-palmitolyl-1,6-dihydroxy-5,7-dimethoxyxanthone) along with n-alkanols, fatty acids, 1,6-dihydroxy-5,7-dimethoxyxanthone, 1,7-dihydroxykanthone, betulinic acid, ${\beta}-sitosterol$, methyl 4-hydroxybenzoate, quercetin, and kaempferol from the aerial parts of Hypericum ascyron was reported. The structures were elucidated by spectroscopic methods, mainly NMR and mass spectrometry.