Activity Of Green Tea Extract Research Articles

엽차용 녹차 추출물 및 분획물의 항균효과

Antimicrobial activities of green tea extracts used for coarse tea were investigated by disc diffusion method using eight different bacteria. Among the green tea extracts, the 70% ethanol extract demonstrated the strongest antimicrobial activities against Vibrio parahemolyticus (V. parahemolyticus) and Staphylococcus aureus (S. aureus) and thus was further fractionated. Among these fractions, the ethyl acetate fraction showed the strongest antimicrobial activities against V. parahemolyticus, S. aureus, Bacillus subtilis (B. subtilis), and Streptococcus mutans (S. mutans). These activities exceeded that of all extracts and fractions tested in this study. Interestingly, although green tea extracts showed significant antimicrobial activity against Micrococcus luteus (M. luteus), once fractionated, the ethyl acetate fraction did not show any antimicrobial activity against M. luteus. MICs of the ethyl acetate fraction were 5 μL/disc against B. subtilis and 3 μL/disc against S. aureus, S. mutans and V. parahaemolyticus. 90% inhibition of B. subtilis was observed with 0.05% ethyl acetate fraction but S. mutans needed over 0.1% ethyl acetate fraction to exhibit the same inhibition as B. subtilis. Antimicrobial activities of ethyl acetate fractions were reduced around 10% by thermal treatment at 121 o C for 20 min. All the results suggest that the 70% ethanol extract as well as the ethyl acetate fraction

Effect of water quality on the nutritional components and antioxidant activity of green tea extracts

Green tea extracts (GTEs) were prepared with tap water (TW), activated carbon adsorbed water (AC), deionized water (DI), distilled water (DW), reverse osmosis water (RO) and ultra-pure water (UP). Their nutritional components were determined by chemical methods. Deoxyribose assay and the xanthine oxidase method were applied to test the antioxidant activities of GTE in vitro. The results indicated that there were statistically significant differences ( P < 0.05) in the yield rate, the contents of polyphenols, catechins, caffeine, copper, lead and fluorine. Among them, DI gave the greatest yield rate and polyphenols, with low caffeine, DW increased the contents of non-ester catechins and AC enhanced the concentrations of ester catechins. The contents of copper and lead in GTEs were highly correlated with those of the tested water ( r = 0.767 and 0.871, respectively). Fluorine contents in all GTEs were above 6.0 g kg −1. GTEs prepared with RO displayed the highest antioxidant activities among the six GTEs.

Comparison of Antioxidant Activity of Green Tea Extract to Commercial Antioxidants in 2% Hydroquinone Cream

ABSTRACT Powdered dry leaves of green tea were extracted with methanol. Green tea extract was tested for antioxidative activity in comparison with antioxidants (sodium metabisulfite and butylated hydro-xytoluene) at 0.1,0.5,1.0, and 2.0% w/w in 2% w/w hydroquinone cream. The systems were incubated in a dark room at 25°C ± 0.5°C and 45°C ± 0.5°C for 3 months. The physical stability and the percentages of hydroquinone remaining after 2 weeks and 1, 2, and 3 months were determined by UV spectrophotometry at 294 nm according to official standard procedures. The experiment revealed that oxidation degradation of hydroquinone was accelerated by heat even with existence of antioxidants. The green tea extract at 1.0 and 2.0% can be used as a double action (both water- and oil-soluble) antioxidant, having 77 and 81% (at 25°C), and 58 and 62% (at 45°C) hydroquinone remaining, respectively, after 3 months. These results suggested the possibility of using the green tea extract as an effective natural antioxidant for substances that are oxidation-susceptible.

Medilite 침출수에 의한 녹차 추출물의 항산화 활성연구

천연 미네랄 성분을 함유한 medilite 침출수를 이용한 녹차 추출물에 의한 화학적 성분조성과 항산화 활성을 증류수 침출 녹차 추출물과 비교하였다. 항산화 활성은 DPPH법 및 microsone 생체막 지질 과산화물 생성정도를 나타내는 TBARS법으로 측정하였다. 녹차 추출물의 총 폴리페놀성 화합물과 추출 수율은 medilite 325 mesh, 600 mesh, DW 추출물 순으로 나타났다. DPPH법에 의한 0.05%와 0.1%의 녹차 추출물에서 항산화 활성은 60.95% ∼ 64.15% 사이였다. 간 homogenate 및 microsone 생체막 지질 과산화물 생성 억제 정도는 medilite 325 mesh 및 600 mesh 침출 녹차 추출물에 비해 증류수 침출 녹차 추출물에서 현저히 억제되었다. 특히 Fe 함량은 증류수 침출 녹차 추출물에 비해 medilite 325 mesh 및 600 mesh 침출 녹차 추출물에 현저히 높았다 이러한 medilite 침출 녹차 추출물에서 높은 Fe성분 함량은 microsone 생체막 지질 과산화물의 생성 촉진과 관련된 것으로 사료된다. 이상의 결과에서 녹차 추출물 중의 총 폴리페놀성 화합물, 추출 수율 및 미네랄 성분은 증류수에 비해 medilite 침출수를 이용함으로써 대체적으로 증가하는 결과를 얻었다. The chemical compositions and antioxidant activity of green tea extracts in medilite-extraction water were compared to that of distilled water(DW). Antioxidant activity was fetermined by the formation of thiobarbituric acid reactive substances (TBARS) in rat liver homogenates and microsomes and the scavenging activity of free radicals by DPPH (<TEX>$\alpha$</TEX>, <TEX>$\alpha$</TEX>'-diphenyl-<TEX>$\beta$</TEX>-picrylhydrazyl). The order of total polyphenolic compounds and extracted yield by extracts was medilite 325 mesh-extraction water, medilite 600 mesh-extraction water and distilled water(DW). The ranges of scavenging activity of green tea extracts in DPPH method were 60.95% - 64.51%. The inhibition ratios of TBARS formation in the rat liver homogenates and microsomal fractions were significantly lower with green tea extracts by DW-extraction than with both medilite 325 mesh and 600 mesh-extraction water. The concentration of iron ion of water containing medilite 325 mesh and green tea extracts and of water containing medilite 600 mesh and green tea extracts were significantly higher compared to DW. Therefore, this result suggested that enhanced concentration of iron ion in green tea extracts by medilite-extraction water containing high iron ion content was associated with enhanced peroxidation of the rat liver microsomal fractions. These results showed that total polyphenolic compounds, the % of yield and mineral compounds of green tea extracts were increased using medilite 325 mesh and 600 mesh-extraction water.

Green Tea Extract is an Effective Antioxidant for Retarding Rancidity of Yukwa (Rice Snacks) Fried in Soybean and Rice Bran Oils

Yukwa is a popular Korean traditional fried rice snack. The high fat content and porous structure of Yukwa cause it to rapidly become rancid, presenting difficult challenges for commercial distribution. In this study, antioxidant activities of green tea extracts (GTE) were evaluated in Yukwa fried in soybean oil (SBO), rice bran oil (RBO) and winterized rice bran oil (WRBO) during storage at 40℃ for 12 weeks. Lipid oxidation of Yukwa was determined by acid value (AV), peroxide value (POV), p-anisidine value (AnV), totox value and sensory evaluation. The addition of GTE to the oils reduced the increases in AV, POV, AnV, and totox. Totox increased most rapidly in Yukwa fried in SBO, followed by RBO＞WRBO＞SBO＋200 ppm GTE＞RBO＋200 ppm GTE＞ WRBO＋200 ppm GTE (p＜0.05). Sensory evaluation revealed that the addition of 200 ppm GTE delays rancidity in Yukwa by 7～8 weeks; providing compelling evidence that GTE is an effective antioxidant for Yukwa.

Antioxidant Activity of Green Tea Extract in Soybean and Rice Bran Oils

Antioxidant activity of green tea extracts (GTE) was evaluated in soybean oil (SBO), rice bran oil (RBO) and winterized rice bran oil (WRBO) stored at 63℃ for 36 days. Lipid oxidation of the oils was determined using the active oxygen method (AOM), peroxide value (POV), change in unsaturated free fatty acid concentrations and by sensory evaluation. SBO had a higher concentration of the polyunsaturated fatty acids, linoleic and linolenic acid than RBO and WRBO. WRBO and RBO were more stable against lipid oxidation than SBO. Addition of GTE (200 ppm) to the stored oils, increased the induction period (IP) in AOM, reduced the increase in POV, and lessened the change in unsaturated fatty acids. Furthermore, GTE prevented the development of rancid flavors resulting from storage, all of which demonstrate the protective antioxidative activity of GTE. However, oil color became darker in the GTE treated oils. The antioxidant protection of GTE was most effective in RBO.

Bactericidal Action of Green Tea Extract and Damage to the Membrane of Escherichia coli O157:H7.

The antibacterial activity of green tea extract was investigated on 36 isolates of pathogens. The minimum inhibitory concentration of the extract against some isolates such as Escherichia coli O157: H7 was less than 250 μg/ml. The growth of the organism in culture broth was completely inhibited with 500 μg/ml of the extract. The organism was not detected by culturing on agar plates after 6 h incubation in phosphate buffered saline with 1, 000 μg/ml of the extract. It was observed by fluorescence microscopy and scanning electric microscopy that the cell membranes were damaged with 1, 000 μg/ml of the extract.

Identification and antioxidant activity of several pigments from the residual green tea (Camellia sinensis) after hot water extraction.

Antioxidant activity of green tea extract or tea-derived polyphenols has been extensively studied. However, antioxidant activity in the non-polyphenolic fraction of green tea has been poorly analyzed. In the present study, we analyzed the antioxidant activity of the non-polyphenolic fraction of the residual green tea (Camellia sinensis) after hot water extraction using the aluminum chloride method. The non-polyphenolic fraction of residual green tea caused a significant suppression against hydroperoxide generation from oxidized linoleic acid in a dose-dependent manner. When the concentrate of the non-polyphenolic fraction was applied to a silica gel TLC plate and developed, six color spots were observed, which were considered to be chlorophylls a and b, pheophytins a and b, carotenoids, such as beta-carotene and lutein according to their specific colors, Rf values of silica gel TLC and spectrophotometric properties. Among these pigments, pheophytins a and b showed relatively abundant amounts, and the second major group of the pigment was chlorophylls a and b, and carotenoids such as beta-carotene and lutein indicated lower concentrations. Although all these pigments exhibited significant antioxidant activities, the ranks of suppressive activity against hydroperoxide generation were chlorophyll a > lutein > pheophytin a > chlorophyll b > beta-carotene > pheophytin b. These results suggest that the non-polyphenolic fraction of residual green tea has a potent suppressive activity against hydroperoxide generation from oxidized linoleic acid, which is derived from the antioxidant activities of chlorophylls a and b, pheophytins a and b, beta-carotene and lutein. This finding also implies that the combined intake of polyphenols in water-soluble fraction and antioxidative pigments in the non-polyphenolic fraction of green tea will be more efficient to prevent life style-related chronic diseases.

Antioxidative activity of green tea treated with radical initiator 2, 2'-azobis(2-amidinopropane) dihydrochloride.

This study investigated the antioxidative activity of green tea extract, and a green tea tannin mixture and its components, under conditions of radical generation using the hydrophilic azo compound, 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) to generate peroxyl radicals at a constant and measurable rate in the cultured renal epithelial cell line, LLC-PK(1), which is susceptible to oxidative damage. Treatment with AAPH decreased cell viability and increased the formation of thiobarbituric acid-reactive substances. However, green tea extract, and the tannin mixture and its components, comprising (-)-epigallocatechin 3-O-gallate (EGCg), (-)-gallocatechin 3-O-gallate (GCg), (-)-epicatechin 3-O-gallate (ECg), (-)-epigallocatechin (EGC), (+)-gallocatechin (GC), (-)-epicatechin (EC), and (+)-catechin (C), showed protective activity against AAPH-induced cellular damage. The tannin mixture and its components exhibited higher antioxidative activity than the green tea extract. Furthermore, EGCg and GCg had higher activity than EGC and GC, respectively. In particular, EGCg exerted the most significant cellular protective activity against AAPH. These results indicate that green tea tannin may inhibit cellular loss and lipid peroxidation resulting from the peroxyl radical generated by AAPH, and that the chemical structure of tannin is also involved in the activity, suggesting that the O-dihydroxy structure in the B ring and the galloyl groups are important determinants for radical scavenging and antioxidative potential.

Antioxidant and pro-oxidant activity of green tea extracts in marine oils

The activity of green tea extracts (GTE) on the oxidation of refined, bleached and deodorized (RBD) seal blubber oil (SBO) and menhaden oil (MHO) was examined under Schaal oven conditions at 65 °C. Progression of oxidation was monitored using weight gain, peroxide value (PV) and 2-thiobarbituric acid-reactive substances (TBARS) data. GTE exhibited a pro-oxidant effect in both oils examined, perhaps due to the catalytic effect of their chlorophyll constituents. Therefore, in follow-up experiments, a column chromatographic technique was employed to remove chlorophyll from GTE. The resultant dechlorophyllized green tea extract (DGTE) was applied to both SBO and MHO at 100, 200, 500 and 1000 ppm levels. The antioxidant activity of DGTE was compared with the effects of the commonly-used antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) at 200 ppm and α-tocopherol at 500 ppm. DGTE at ≥200 ppm exhibited excellent antioxidant activity in both oils and its efficacy was higher than that of BHA, BHT and α-tocopherol, but less than that of TBHQ.

Inhibition of N-nitrosation of secondary amines in vitro by tea extracts and catechins

Inhibition of nitrite-mediated N-nitrosation of dimethylamine, morpholine and N-methylaniline by tea extracts and by 6 individual catechins in the extracts was studied. The inhibitions were detected by quantifying the nitrosamines formed. Eight different kinds of teas (5 green teas, a roasted green tea, an oolong tea, and a black tea) were examined for their inhibitory abilities and for their catechin contents, with an attempt to correlate the inhibitory activities to the catechin contents. The results showed that (1) the green tea extracts inhibit strongly the N-nitrosation of the three secondary amines tested, (2) the 6 catechins, notably epigallocatechin, are capable of blocking the N-nitrosations very efficiently, even more efficiently than ascorbic acid, and (3) the inhibition activities of green tea extracts are mostly ascribable to the catechins present in the extracts. These inhibitions occur by rapid reactions between nitrite and the catechins. It was observed that no mutagenicity results from the reaction between the tea extracts and nitrite.

Potent suppressing activity of the non-polyphenolic fraction of green tea ( Camellia sinensis) against genotoxin-induced umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002) – association with pheophytins a and b

Antigenotoxic and antimutagenic activities of green tea extract and tea-derived polyphenols have been studied using in vitro and in vivo experiments. However, antigenotoxic substances in the non-polyphenolic fraction of green tea have been poorly elucidated. In the present study, the effect of the non-polyphenolic fraction of green tea on genotoxin-induced umu C gene expression was analyzed using a tester bacteria, and potent antigenotoxic substances in the non-polyphenolic fraction were identified. The non-polyphenolic fraction of green tea showed strong suppressive activities against umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002) induced by 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indol (Trp-P-1) or mitomycin C (MMC) in the presence or absence of S9 metabolizing enzyme mixture. The non-polyphenolic fraction of green tea exhibited major two-color bands in a silica gel TLC and they were identified as chlorophyll-related compounds, pheophytins a and b, judged by their specific colors, R f values in silica gel TLC and absorption spectra. These pigments showed significant suppressive activities against umu C gene expression in tester bacteria induced by Trp-P-1 and MMC in a dose-dependent manner. These results suggest that the non-polyphenolic fraction of green tea contains pheophytins a and b as potent antigenotoxic substances.