Activity Of Green Tea Polyphenols Research Articles

Antibacterial activity of green tea polyphenols against Escherichia coli K 12.

Antibacterial activity of green tea polyphenols against Escherichia coli K 12.

Antidiscoloring Activity of Green Tea Polyphenols on β-Carotene

The antidiscoloring activity of green tea polyphenols and catechins on β-carotene was investigated. The residual ratio of β-carotene added in beverages and margarine was measured. Green tea polyphenols showed dose-dependent antidiscoloring activity of β-carotene on both the beverage and the margarine. The antidiscoloring effect of (−)-epigallocatechin 3-gallate (EGCg) and l-ascorbate (Vc) in a buffer solution (pH 4.0) containing β-carotene was compared under fluorescence irradiation. At 1000 μM, EGCg and Vc maintained residual β-carotene amounts of 85.4% and 78.5% and at 100 μM 79.6% and 2.9%, respectively. The strength of the antidiscoloring activity of the catechins, gallic acid (GA), and Vc was as follows: (−)-gallocatechin 3-gallate, (−)-epigallocatechin, EGCg, (+)-gallocatechin ≫ GA > Vc, (−)-epicatechin, (+)-catechin. It was suggested that the hydroxyl group at the 5‘-position of the B ring of the catechin skeleton mostly contributed to the antidiscoloring activity. Keywords: Green tea; catechins; ...

ANTIOXIDATIVE ACTIVITY OF GREEN TEA POLYPHENOLS IN EDIBLE OILS

ABSTRACTThe antioxidant activity of green tea polyphenols in several edible oils and fried noodle was investigated. The green tea polyphenols consisted of 27.1% (−)‐epigallocatechin‐3‐gallate, 19.3% (+)‐gallocatechin, 16.7% (−)‐gallocatechin‐3‐gallate, 16.1% (−)‐epigallocatechin, 8.1% (−)‐epicatechin‐3‐gallate, 7.5% (−)‐epicatechin, and 5.2% (+)‐catechin. The antioxidant effect of green tea polyphenols in lard and soybean oil was dose‐dependent, but tocopherol was less effective. Compared to BHA and tocopherol, green tea polyphenols showed a stronger antioxidative activity on fish oil. Noodles were fried in lard containing green tea polyphenols at several concentrations. The oxidative stability of the noodle was proportional to the green tea polyphenol concentration in lard.

Anticarcinogenic Activity of Green Tea Polyphenols

The main physiologically active polyphenol in green tea extract is (-)-epigallocatechin gallate (EGCG). Green tea extract has an advantage over EGCG as a cancer chemopreventive agent for humans, as is apparent from the Japanese custom of injesting green tea on a daily basis. Green tea extract similarly inhibited protein kinase C activation by teleocidin, a tumor promoter, as did EGCG. In addition, EGCG and green tea extract showed inhibitory effects on the growth of lung and mammary cancer cell lines with similar potencies. An experiment using the estrogen-dependent MCF-7 cell line showed the mechanisms of action of these compounds to be inhibiting the interaction of estrogen with its receptors. Considering our previous results of a single application of EGCG to mouse skin inhibiting the specific binding of 3H-12-0-tetradecanoylphorbol-13-acetate (3H-TPA) and 3H-okadaic acid, we postulated that EGCG and compounds in green tea extracts would block the interaction of tumor promoters, hormones and growth factors with their receptors: a kind of sealing effect. The sealing effect would account for reversible growth arrest, and may be induced by various kinds of compound.

Antimutagenic activity of green tea polyphenols

For centuries green tea has been a widely consumed beverage throughout the world. It is known to contain a number of pharmacologically active compounds. In this study water extracts of green tea (WEGT) and their major constituents, green tea polyphenols (GTP), were examined for antimutagenic activity. WEGT and GTP were found to significantly inhibit the reverse mutation induced by benzo[ a]pyrene (BP), aflatoxin B 1 (AFB 1), 2-aminofluorene, and methanol extracts of coal tar pitch in Salmonella typhimurium TA100 and/or TA98 in the presence of a rat-liver microsomal activation system. GTP also inhibited gene forward mutation in V79 cells treated with AFB 1 and BP, and also decreased the frequency of sister-chromatid exchanges and chromosomal aberrations in V79 cells treated with AFB 1. The addition of GTP during and after nitrosation of methylurea resulted in a dose-dependent inhibition of mutagenicity. Studies to define the mechanism of the antimutagenic activity of GTP suggest that it may affect carcinogen metabolism, DNA adduct formation, the interaction of ultimate carcinogen or the scavenging of free radicals.