• Environmental Mutagens and Carcinogens
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• v.19 no.2
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• pp.116-121
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• 1999

Quercetin and its glycosides showed a strong free radical scavenging effect to DPPH radical generation. However, there were not big differences between quercetin aglycone and glycosides under experimental condition of this study. On the other hand, quercetin had pro-oxidant effect in bleomycin-dependent DNA assay. Quercetin aglycone and its glycosides, quercitrin inhibited $H_2$$O_2$- induced DNA damage in CHL cells. They also have an anticlastogenicity toward DNA breakage agent by radical generation like bleomycin. These results indicate that quercetin aglycone and its glycosides are capable of protecting the free radical generation induced by reactive oxygen species like $H_2$$O_2$. The mechanism of inhibition in hydrogen peroxide-induced genotoxicity may be due to their free radical scavenging properties. Therefore, quercetin aglycone and its glycosides may be useful chemopreventive agents by protecting of free radical generation which are involved in carcinogenesis and aging. However, quercetin and its glycosides must also carefully examined for pro-oxidant properties before being proposed for use in vivo.

• Food Science of Animal Resources
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• v.21 no.4
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• pp.389-394
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• 2001

This study was conducted to investigate the flavonoid contents of Korean propolis. The total flavonoids content measured by spectrophotometer of Yecheon, Youngwol, Brazilian, Chinese. Aus- tralian propolis were 6.33, 6.43, 2.44, 6.52 and 8.11mg/g. The p-coumaric acid content of Yecheon and Youngwol propolis were 5.58 and 6.84mg/100g, respectively. Luteolin, however, was not detected both in Yecheon and Youngwol, respectively. the quercetin content of Yecheon and Youngwol propolis revealed between 0.41 to 0.53%, however, overseas propolis was not detected. The t-cinnamic acid of Brazilian propolis was 7.92% and Chinese propolis was 8.74%. And than, the t-cinnamic acid of Chinese propolis was not detected.

• Korean Journal of Pharmacognosy
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• v.30 no.1
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• pp.34-39
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• 1999

To search for less toxic antiherpetic agents, the inhibitory effects of twelve kinds of flavonoids including chrysin, quercetin, quercitrin, rutin, fisetin, gossypin, kaempferol, morin, naringenin, naringin, hesperetin and hesperidin on the plaque formation of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in Vero cells were examined by plaque reduction assay in vitro. Some flavonoids tested in this study showed potent antiherpetic activity, reducing intracellular replication of herpes simplex viruses when Vero cell monolayers were infected and subsequently cultured in medium containing flavonoids. Naringenin showed the most potent antiviral activity against HSV-1 with selectivity index (SI) of 19.1 and hesperetin showed the most potent antiviral activity against HSV-2 with SI of 9.8. These results suggest that some flavonoids may be a potential therapeutic agent for the treatment and prevention of herpes simplex virus infections.

• Korean Journal of Pharmacognosy
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• v.44 no.1
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• pp.16-21
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• 2013

The fruits of Pourthiaea villosa were extracted with methanol and its extract was fractionated with n-hexane, methylene chloride, ethyl acetate and n-butanol. Repeated column chromatography of silica gel, sephadex LH-20 and HPLC led to the isolation of nine phenolic compounds from ethyl acetate soluble fraction. The chemical structures were elucidated as kaemferol-3-O-${\beta}$-D-glucopyranoside (astragalin) (1), isorhamnetin-3-O-${\beta}$-D-glucopyranoside (2), kaempferol-3-O-${\beta}$-D-xylopyranosyl($1{\rightarrow}2$)-${\alpha}$-L-rhamnopyranoside (3), caffeic acid (4), quercetin-3-O-${\beta}$-D-xylopyranosyl($1{\rightarrow}2$)-a-L-rhamnopyranoside (5), quercetin-3-O-${\beta}$-D-xylopyranosyl($1{\rightarrow}2$)-${\beta}$-D-glucopyranoside (6), quercetin-3-O-${\beta}$-D-xylopyranosyl($1{\rightarrow}2$)-${\beta}$-D-galactopyranoside (7), quercetin-3-O-${\alpha}$-L-rhamnopyranoside (quercitrin) (8), and kaempferol-3-O-${\alpha}$-L-rhamnopyranoside (afzelin) (9) by spectroscopic techniques. These compounds were isolated from this plant for the first time.

• Natural Product Sciences
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• v.20 no.3
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• pp.191-195
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• 2014

The n-BuOH soluble fraction of the whole plant of Persicaria thungergii showed acetylcholinesterase inhibitory activity. Four flavonoid glycosides and a flavonoid were isolated from this fraction, and identified as quercitrin (1), luteolin-4'-O-${\beta}$-D-glucopyranoside (2), quercetin (3), quercetin-3-O-glucuronide (4), and isorahmnetin-3-O-glucuronid (5), by chromatographed and spectral data, respectively. All isolated compounds were showed acetylcholinesterase inhibitory activity, with $IC_{50}$ values of 243.1, 10.5, 39.1, 8.2 and $23.2{\mu}M$, respectively.

• Natural Product Sciences
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• v.12 no.4
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• pp.210-213
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• 2006

A 4,5-dioxoaporphine type alkaloid, cepharadione B (1), a phenolic acid, protocatechuic acid (2), and flavonols, quercetin (3), afzelin (4), and quercitrin (5), were isolated from the EtOAc-soluble extract of the whole plants of Houttuynia cordata. All the isolates (1-5) were subjected to in vitro bioassays to evaluate advanced glycation end products (AGEs) formation and rat lens aldose reductase (RLAR) inhibitory activity. The three flavonols 3-5 exhibited a significant inhibitory activity on AGEs formation with $IC_{50}$ values of 66.9, 58.9, and $32.3{\mu}M$, respectively. While the two flavonol rhamnosides 4 and 5 showed a remarkable inhibitory activity against RLAR with $IC_{50}$ values of 0.81 and $0.16{\mu}M$, respectively.

• Archives of Pharmacal Research
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• v.28 no.5
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• pp.529-533
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• 2005

In the course of searching for hepatoprotective agents from natural products, six compounds were isolated from the MeOH extract of the leaves of Juglans sinensis, as guid ed by their DPPH free radical scavenging activity. The structures were determined as juglanoside B (1), quercetin 3-O-${\alpha}$-L-arabinofuranoside (avicularin, 2), quercetin 3-O-${\alpha}$-L-arabinopyranoside (guaijaverin,3), quercetin 3-O-${\alpha}$-L-rhamnopyranoside (quercitrin,4), (+)-catechin (5) and quercetin 3-O-${\beta}$- D-galactopyranoside (hyperin,6). Compounds 2-6 showed significant DPPH free radical scavenging effects. An evaluation for the hepatoprotective activity of the isolated compounds on drug-induced cytotoxicity was conducted, and compounds 1, 2, and 5 showed protective effects against nitrofurantoin-induced cytotoxicity, and compound 5 also exhibited a moderate protective effect on amiodarone-induced cytotoxicity in Hep G2 cells.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.4
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• pp.682-686
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• 1998

To use onion(Allium cepa L.) residue as raw materials of food products, contents and stability of quercetin-related substance in onion were investigated. The amount of quercetin-related substance of onion was richer in the inedible portion(317.99mg%) than the edible protion(4.10mg%). Total quercetin-related substances of juice and residue from fresh onions were 2.26mg% and 1.57mg%, respectively, but they were changed to 1.50mg% and 2.96mg% by heating at 8$0^{\circ}C$ for 10min. Quercetin was found to be stable at 20$0^{\circ}C$ for 60 min, but it was unstable to light. When it was illuminated with 30W, the content was decreased and reached to 80~85% of the original content after 48 hours. Quercetin was not affected by pH, but quercitrin and rutin were unstable below pH 5.

• Food Science and Preservation
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• v.4 no.2
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• pp.181-187
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• 1997

New HPLC method was developed for determination of some flavonoids such as naringin, hesperidin, neohesperidin, rutin, quercitrin, naringenin, hesperetin and apigenin and their contents in citrus juice and citrus peel from citrus varieties Brown in Cheju. Detection was at 280nm and reverse phase ${\mu}$-Bondapak C-18 column was used. Water/methanol/acetic acid as the mobile phase was better than water/acetonitrile/acetic acid. Flavonoids were more stable in 20% n,n-dimethylformamide in methanol(20% DMF) than methanol and pH 12 adjusted by 1N-sodium hydroxide solution. Standard flavonoid solutions were injected three times consecutively and the reproduciability was 0.236 to 3.550%, Correlation coefficient of the calibration curve was 0.9946 to 0.9999. The exiraction efficiency of hesperidin from citrus peel was evaluated with different extraction method such as reflux, ultra-sonicating method, using three solvents (aqueous solutions with pH12 adjusted by 1N-sodium hydroxide, methanol and 20% DMF), respectively. The reflux for 4 hour in 20% DMF was the most efficient of the tested methods and solvents, and recovery percentage were 78.0∼130.0%. Flavonoids were determined in citrus juice. Naringin was 68.2mg/100$m\ell$ in Natsudaidai, Hesperidin were 85.6mg/100$m\ell$ in Sankyool and Neohesperidin was 25.3mg/100$m\ell$ in Dangyooja. Flavonoids were determined in citrus peel. Naringin was 110mg/g in Dangyooja, Hesperidin was 242mg/g in Hungjin and Neohesperidin was 87.9mg/g in Dangyooja.

• Natural Product Sciences
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• v.22 no.1
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• pp.64-69
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• 2016

A method for simultaneously identifying antioxidative compounds was developed using time-based LC-MS coupled with DPPH assay regardless of the time consuming process. The methanolic extract of Polygonum aviculare (Polygonaceae) showed significant DPPH radical scavenging activity. Time-based DPPH assay for simultaneous identification of active compounds from the extracts of P. aviculare was used. Major peaks of ethyl acetate fraction of P. aviculare showed high DPPH radical scavenging activity. A simple phenolic compound (1) and six flavonoids (2-7) were isolated from the ethyl acetate fraction of P. aviculare by silica gel and sephadex LH-20 column chromatography. The structures of seven compounds were determined to be protocatechuic acid (1), catechin (2), myricitrin (3), epicatechin-3-O-gallate (4), avicularin (5), quercitrin (6), and juglanin (7) based on the analysis of the $^1H$-NMR, $^{13}C$-NMR and ESI-MS data. All compounds exhibited significant antioxidant activity on DPPH assay and active compounds were well correlated with predicted one.