• Korean journal of food and cookery science
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• v.31 no.5
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• pp.581-587
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• 2015

This study was conducted to investigate the antioxidative and antimicrobial activities of Korean dandelion (Taraxacum coreanum). Water extracts, ethanol extracts and methanol extracts were used to examine the free radical scavenging activity, total flavonoid content, total polyphenol content and antimicrobial activity. The free radical scavenging activity, total flavonoid, total polyphenol and total antioxidant activity of the water extracts were higher than those of the other extraction solvents. The antimicrobial activties of Korean dandelion extracts were examined on several food borne illness microorganisms using the paper disc diffusion method. Inhibition zones were observed on Staphylococcus aureus subsp. aureus, Listeria monocytogenes, Bacillus subtilis, Bacillus cereus and Escherichia coli in ethanol extracts. Inhibition zones were also observed on Listeria monocytogenes in water extracts. The physico-chemical properties of Korean dandelion tea according to the roasting time and soaking amount of tea were studied. The pH of the dandelion tea significantly decreased while the soluble solid contents significantly increased with increased roasting time (p<0.01). The lightness of the dandelion tea decreased and the turbidity increased with increased roasting time. In sensory evaluation, the sensory scores for the color, flavor and total acceptability were highest in the 40 min roasted tea. These results suggest that the water extract of Korean dandelion could be used as an antioxidative and antimicrobial functional food source. The optimum roasting time for Korean dandelion tea was 40 min at $200^{\circ}C$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.2
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• pp.299-304
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• 1995

Antioxidative effect of tea extracts from green tea(steamed, roasted), oolong tea and black tea was investigated. Antioxidative activities of the crude catechin fraction were the most effective in oolong tea which contained the highest level of (-)-epigallocatechin gallate(EGCg). The water-soluble fraction obtained from oolong tea exhibited binding with more ferrous than copper ions. It showed a synergistic effect when used with an antioxidant such as BHT(0.5mg) and $\alpha$-tocopherol(2mg). Especially, this synergistic effect was exhibited more with BHT than with $\alpha$-tocopherol. Also steamed green tea, roasted green tea and oolong tea showed remarkable free radical scavenging action. The SC50(the concentration of a water-soluble fraction which is required to scavenge 50% of 100$\mu$M 1, 1-diphenyl-2-picryl hydrazyl radicals) of steamed and roasted green tea, oolong tea and black tea extracts were 11.3$\mu\textrm{g}$/ml, 11.4$\mu\textrm{g}$/ml, 12.7 $\mu\textrm{g}$/ml and 14.9$\mu\textrm{g}$/ml, respectively. It is assumed that the antioxidative activity of tea extracts is due to inhibition of peroxidation free radical scavenging and binding action of ferrous ions by mainly tea polyphenol compounds.

• Archives of Pharmacal Research
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• v.29 no.9
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• pp.786-794
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• 2006

We observed the suppressive effect of a powder formulation of African black tea extract prepared from the leaves of Camellia sinensis on type 2 non-insulin dependent diabetic mice, $KK-A^y/TaJcl$. Black tea extract significantly showed suppressive effect of the elevation of blood glucose on oral glucose tolerance test of 8 week-old $KK-A^y/TaJcl$ mice (p<0.05). Long-term treatment with black tea extract showed significant suppression of post-prandial blood glucose and obesity (p<0.05). The weight of the intestine of mice treated with black tea extract was significantly reduced (p<0.05). From these results, African black tea used in this study showed a suppressive effect on the elevation of blood glucose during food intake and the body weight.

• Food Science and Biotechnology
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• v.18 no.4
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• pp.932-938
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• 2009

Browning of tea infusion is an obstructive factor influencing shelf life of ready-to-drink green tea. Effects of temperature and illumination on the browning of green tea infusion were investigated. It was shown that both elevated temperature and illumination led to the browning of green tea infusion, but temperature had greater effect on infusion color and level of catechins than illumination. The levels of unoxidized catechins such as (-)-epigallocatechin gallate (EGCg), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), (-)-epicatechin (EC), and total catechins remaining in the tea infusion were significantly correlated to color parameters of the tea infusion. Sodium ascorbate inhibited the infusion browning by suppressing the oxidation of tea catechins and it is considered to be a more suitable preservative for prolonging shelf life of ready-to-drink green tea than ascorbic acid because it has less effect on tea taste. The effects of temperature and illumination on the epimerization of catechins were also discussed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.8
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• pp.1073-1078
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• 2011

Changes of antioxidative components and activity of fermented tea manufactured by Bacillus subtilis, Saccharomyces cerevisiae, and Lactobacillus bulgaricus were evaluated during the fermentation period. The ascorbic acid content in the fermented tea was relatively lower (43.62~62.84 mg%) than that of green tea (66.74 mg%) during the entire fermentation period. The tea fermented by L. bulgaricus, which had the least contact with air, showed less change in ascorbic acid content. The polyphenol content of green tea was 14.88%, whereas that of fermented tea was 11.54~14.12% and it decreased during the fermentation period. The amount of flavonoids in green tea was 7.78 mg%, whereas that of fermented tea was 4.33~7.88 mg%. DPPH radical scavenging activity and ABTS reducing activity of green tea were 87.47% and 203.22 AEAC mg% (ascorbic acid equivalent antioxidant capacity), respectively, whereas those of fermented tea were lower than green tea. Results indicated that the antioxidative components and activity of fermented tea were lower than those of green tea during the fermentation period. But, when the sensory and hygienic quality are considered, fermented tea can be one of the higher quality tea products on the market.

• Horticultural Science & Technology
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• v.35 no.2
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• pp.252-264
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• 2017

Tea is one of the most consumed beverages worldwide and the relatively high levels polyphenols is benefit for health. In this study, we developed an efficient system for proliferation of callus from 'Anji Baicha', a cultivar of tea (Camellia sinensis). Callus tissue was initially induced by culturing leaf explants on medium containing different plant growth regulators. For callus induction, thidiazuron (TDZ) was more effective than 2,4-dichlorophenoxyacetic acid (2,4-D), ${\alpha}-naphthalene$ acetic acid (NAA), and $N^6-benzyladenine$ (BA). The frequency of callus induction from leaf explants reached 90.21% on $1.0mg{\cdot}L^{-1}$ TDZ and the developed callus was reddish and friable. We also tested the effect of different concentrations of NAA, 2,4-D, indole 3-acetic acid (IAA), BA, and TDZ, alone and in combinations, on callus proliferation. Medium supplemented with TDZ in combination with IAA was suitable for callus proliferation and accumulation of tea polyphenols. The growth index value and tea polyphenol content of callus cultured on MS medium containing $0.5mg{\cdot}L^{-1}$ TDZ and $1.0mg{\cdot}L^{-1}$ IAA was maximally 1,351% and 23.24%, respectively, and the relative abundance of epicatechin was as high as 17.449%. We also measured the antioxidant activity of all samples and the callus with the highest tea polyphenol content also exhibited high potential radical scavenging activity.

• Journal of Applied Biological Chemistry
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• v.55 no.1
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• pp.19-25
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• 2012

Green tea leaves were fermented for 15 and 30 days with Monascus pilosus which is known to produce functional statins (TMs), and the content of various biochemical constituents such as total polyphenol (TP), total flavonoid (TF), theaflavin, and thearubigin were analyzed and compared with that of non-fermented green tea (GT) and Pu-erh Chinese post-fermented tea (PU). In addition to the electron donating ability (EDA), ferric iron reducing power (FIRP), xanthine oxidase (XO) inhibitory activity, superoxide dismutase (SOD)-like activity, iron chelating activity (ICA) and hydrogen peroxide contents were also measured and compared with that of GT and PU. Content of TP and TF in the water and ethanol extracts in TMs were lower than those in GT and PU. Theaflavin and thearubigin contents of water and ethanol extracts in TMs were higher than those of GT. And, these components were increased depending on the period of fermentation. While, EDA and FIRP of TMs were lower than those of GT, XO inhibitory activity of TMs was higher than non-fermented tea. While, ICA of TMs was slightly higher than GT and PU, the content of hydrogen peroxide in TMs was markedly lower than GT. This results suggested that the green tea fermented by M. pilosus was valuable for oxidative stress-induced diseases by decreasing hydrogen peroxide, and forming theaflavins and thearubigins with functionality of genus Monascus.

• KSBB Journal
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• v.23 no.5
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• pp.387-391
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• 2008

Green tea is popular plants in Asian countries and has become more widespread in western countries due to its taste characteristics and health benefits. Apart from green tea leafs, however, the use of root and seed of green tea tree has not intensively been investigated yet. In this study, the contents of mineral, vitamin, total amino acid, free amino acid, and total polyphenol (catechin, caffeic acid, and chlorogenic acid) of the root and seed of green tea tree were analyzed for the development of healthy foods. For minerals, potassium contents were 1,052 and 1,480 mg/100g-dry weight of root and seed, respectively. The order of mineral contents were as follows: K > P > Ca > Mg > Na > Fe > Mn > Zn > Cu in root and K > P > Na > Ca > Mg > Mn > Fe > Cu > Zn in seed. For vitamins, vitamin C contents were 5.72 and 6.05 mg/100g-dry weight of root and seed, respectively. The presence of more various kinds of vitamins were observed in seed than in root. For total amino acids, the contents were 1,651 and 4,335 mg/100g-dry weight of root and seed, respectively. The total amino acid contents of seed and root were higher than those in commercial green tea products. Especially the phenylalanine contents were 16 and 139 mg/100g-dry weight of root and seed, respectively whereas phenylalanine was not found in commercial green tea products. Concerning free amino acids, the bitter tasting amino acids such as arginine, valine and tryptophan were more abundant in root and the sweet tasting ones such as glutamic acid, alanine, aspartic acid, and serine were more abundant in seed. The total polyphenol contents were 237 and 81 mg/100g-dry weight of root and seed, respectively. The polyphenol contents in root were three times higher than that in seed so root may be a better source for antioxidant ingredients than seed. Among many polyphenols, catechin, caffeic acid, and chlorogenic acid were the top three major components.

• Food Science and Preservation
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• v.13 no.5
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• pp.596-602
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• 2006

This study was conducted to investigate the changes of major components and bioactivities of tea produce. The tea produce were made by various methods, with different degree of fermentation during manufacturing process. Except green tea, degrees of fermentation in Wizo Tea, Ilsoae Tea, and Hwang Tea were $5{\sim}10%,\;50{\sim}60%$ and $70{\sim}80%$ respectively. The result are as follows : The general component(moisture, crude ash, crude lipid, and crude protein) and the content of total polyphenol in tea products were not shown significant difference during the fermentation process. The content of caffeine in tea extracts decreased sharply as degree of fermentation of tea. In comparison of hunter values in tea extract, lightness was decreased as fermentation redness (a) was all (-), and yellowness(b) was increased sharpy with degree of fermentation. Radical scavenging activity using DPPH of tow kinds of tea was potent and decreased generally with degree of feimentation. Inhibitory effects of tea extracts against angiotensin I converting enzyme were also potent.

• Korean Journal of Food Science and Technology
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• v.35 no.6
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• pp.1199-1203
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• 2003

Polyphenols were isolated from Korean green tea using Sephadex LH-20 and HPLC. The isolated polyphenols were procyanidin B-4, procyanidin B-2-3,3'-digallate, prodelphinidin C-2-3,3'-di-O-digallate, (+)-catechin-3-O-rhamnose, procyandin B-5, procyanidin B-7-3-0-gallate, gallate, epiafzelechin-$(4{\beta}{\rightarrow}8)$-epiafzelechin, procyanidin B-3-3-O-rhamnose, afzelechin-$(4{\alpha}{\rightarrow}8)$-catechin, prodelphinidin B-5-3,3'-di-O-digallate and (+)-taxifolin-3-O-D-xyloside. The inhibitory effects of prodelphinidin C-2-3,3'-di-O-gallate and procyanidin B-2-3,3'-digallate $(at\;100{\mu}M)$ on angiotensin.converting enzyme were 68.8 and 54.6%, respectively, while the inhibitory effects of prodelphinidin C-2-3,3'-di-O-gallated and procyanidin B-2-3,3'-digallate $(at\;100{\mu}m)$ on xanthine oxidase were 54.5 and 38.2%, respectively. Lastly, the inhibitory activities of prodelphinidin C-2-3,3'-di-O-gallate $(at\;100{\mu}m)$ on tyrosinase was 42.1%.