• Food Science and Preservation
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• v.16 no.2
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• pp.230-237
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• 2009

The phenolic contents, antioxidant effects, and acetylcholinesterase inhibitory activities of hot water extracts prepared from various Korean commercial teas(green tea, puer tea, oolong tea, and black tea) were investigated. Total phenolic contents were in the range 72.03-85.62 mg/g. Flavonol contents of hot water extracts from green tea, puer tea, oolong tea, and black tea were 350.96, 254.17, 334.48, and 240.23 mg/100 g, respectively. Catechin contents were 2,920.35 mg/100 g in green tea, 1,016.23 mg/100 g in puer tea, 2,824.22 mg/100 g in oolong tea, and 1,006.51 mg/100 g in black tea. The highest caffeine content was in the green tea extract. All four extracts scavenged $ABTS^{{\cdot}+}$ radicals in a concentration-dependent manner, and the green tea extract was the most potent in this regard. The highest reducing power was observed in the green tea extract. All four extracts exhibited considerable antioxidative activities in linoleic acid autoxidation, $\beta$-carotene bleaching, and acetylcholinesterase inhibition assays; the effects were concentration-dependent and decreased in the order green tea > oolong tea > puer tea > black tea.

• Journal of Food Hygiene and Safety
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• v.13 no.4
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• pp.370-376
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• 1998

The extraction yield of MeOH extract of green teas, oolong tea and black tea were 3 to 5, 4 to 5, and 5 to 7 fold higher than those of EtOH and EtAC extract, respectively. The amount of total catechins of EtAC extract of the black tea, and of the green teas and oolong tea were three- and two-fold higher than that of EtOH or MeOH extract of the corresponding teas, respectively. The antioxidative activities of EtOH, MeOH and EtAc extract were considerably higher than that of BHT and $dl-{\alpha}-tocopherol$ at 200 ppm level. The antioxidative activities of EtOH and MeOH extract at 200 and 500 ppm level, and of EtAc extract at 200 ppm level varied depending on the type of tea as follows : green tea I > green tea II > green tea III > oo-long tea> black tea. The antioxidative activity increased as the content of EGC increased. But the antioxidative activity of MeOH extract at 1000 ppm level, and of EtAc extract at 500 and 1000 ppm level were not affected by the content of EGC and EGCG.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.9
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• pp.1134-1139
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• 2007

This study was conducted to investigate the effects of four kinds of tea (Camellia sinensis) extracts on the antioxidant defense systems as well as the activities of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) in ethanol administered ICR mice. According to the results, treatment with puerh tea significantly increased the superoxide dismutase activity and glutathion reductase activity in liver. In addition, the group treated with oolong tea exhibited higher superoxide dismutase activity and glutathion reductase activity in serum than those of puerh tea, green tea and black tea treated groups. The oolong tea and puerh tea also reduced malondealdehyde contents in both liver and serum. These results suggested that puerh tea and oolong tea were the most effective against alcohol-induced oxidative damage among the Camellia sinensis teas. On the other hand, in the measurement of alcohol break-down enzyme activities, the group treated with green tea exhibited the highest hepatic ADH and ALDH activities, suggesting that the group treated with green tea might be useful for alcohol down-regulation.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.823-830
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• 1999

The suppressing effects of crude extracts of three Korean teas, persimmon leaf tea extract (PLTE), green tea extract (GTE) and oolong tea extract (OTE), were studied on the induction of sister chromatid exchange (SCE) in cultured Chinese hamster ovary cells. When cells were treated with tea extract after mitomycin C (MMC) treatment, the frequency of MMC-induced SCEs were decreased at the high concentration $(1000\;{\mu}g/mL)$ of PLTE in the presence of S9 mix and at low concentrations $(20{\sim}80\;{\mu}g/mL)$ of PLTE in the absence of S9 mix, Whereas GTE and OTE showed suppressing effects on the MMC-induced SCEs at low concentrations $(10{\sim}20\;{\mu}g/mL)$ for OTE and $160\;{\mu}g/mL$ for GTE only in the presence of S9 mix. MMC-induced SCEs were decreased by post-treatment with each tea extracts with S9 mix in the G1 phase of the cell cycle. These results suggest that PLTE, GTE and OTE could have bio antimutagenic activities, and also suggest that PLTE might have unknown antimutagenic components which would be responsible for the inhibitory effect against direct acting mutagenicity.

• Bulletin of Food Technology
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• v.23 no.2
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• pp.263-269
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• 2010

• Food Science and Industry
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• v.40 no.3
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• pp.59-65
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• 2007

• Korean Journal of Food Science and Technology
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• v.24 no.6
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• pp.558-562
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• 1992

Xanthine oxidase involved in pruine metabolism oxidizes hypoxanthine to xanthine and xanthine to uric acid. The derangement of pruine metabolism results in gout that associates painful deposit of monosodium urate in the cartilage of joints. In the continuous study for natural compound, six flavan-3-ols have been isolated from the leaves of Oolong tea. The structures of procyanidin B-1, B-3, procyanidin B-3-3-O-rhamnose, procyanidin B-1-3-O-gallate, (-)-epicatechin, (-)-epicatechin-3-O-gallate were established by NMR and their inhibitory effect on xanthine oxidase activity was investigated. Flavan-3-ols containing the gallate had a high inhibitory capacity. Procyanidin B-1-3-O-gallate showed complete inhibition at $50\;{\mu}M$ and inhibited on the xanthine oxidase competitively.

• Korean Journal of Food Science and Technology
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• v.28 no.6
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• pp.1084-1088
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• 1996

As a series of study for an anti-gout agent, two flavan-3-ols have been isolated from Oolong tea. They showed positive reaction in $anisaldehyde-H_2SO_4$ solution and $FeCl_3$, which were able to be confirmed in TLC with dimeric flavan-3-ols. The components were identified as procyanidin B-2 and procyanidin B-2-O-3, 3'-di-gallate by spectroscopic analysis. Their inhibitory effect on xanthine oxidase was also investigated and procyanidin B-2-O-3, 3'-digallate showed 60.6% inhibition at $50\;{\mu}mole$. The compound competitively inhibited the xantine oxidase and dimeric flavan-3-ols contanining gallate had higher inhibition activity.

• Korean Journal of Food Science and Technology
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• v.30 no.4
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• pp.970-975
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• 1998

Eighty percent of acetone extract were isolated from the leaves of Korean Oolong tea using Sephadex LH-20, MCI-gel, Fuji gel. The compound reacted the red and the blue with anisaldehyde and $FeCl_3$, respectively. Instrumental analysis of the derivatives of this compound showed that the chemical structure was decided to $epicatechin-(4{\beta}{\rightarrow}8)-epigallocatechin-3-O-gallate$ as a kind of dimeric proanthocyanidine, that bound with -(-)epicatechin and -(-)epigallocatechin-3-O-gallate, at the upper and the lower, respectively. Considering inhibition effect on xanthin oxidase by 62% levels at $50{\;}{\mu}mole$, this compound showed a possibility to be used as a new material for functional food.

• Korean Journal of Food Science and Technology
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• v.38 no.1
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• pp.5-9
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• 2006

Method for separation and quantification of methylxanthins, catechins, and theaflavins in Korean commercial teas (green, oolong, and black teas) was developed using reversed phase high-performance liquid chromatography (HPLC). After extraction with hot water, tea compounds were separated on Inertsil ODS-3v $(5\;{\mu}m)$ column, eluted with gradient of 7% acetonitrile and 93% of 20 mM phosphate buffer mixture for 7 min. Column effluent was monitored at 270 nm. This technique was effective for analyses of m methylxanthins, catechins, and theaflavins in teas and biological samples. In green and oolong teas, two kinds of methylxanthins and 7 of catechins were identified, whereas 4 theaflavins were only identified in black tea. Among seven catechins in green and oolong teas, EGCG showed highest amount, whereas ECG was highest in black tea. (theaflavins were found only in black teas) In all teas, theobromine content was lower than that of caffeine.