Tea tannins

UCHIDA S, OZAKI M, KASHI T, YAMASHITA K, NIWA M and TANIYAMA K (1995) Effects of (-)-epigallocatechin-3-O-gallate (green tea tannin) on the life span of stroke-prone spontaneously hypertensive rats , Clin Exp Pharmacol, 11 (Suppl 1), S302-303. 

Ascorbic acid increases absorption (see above) but its use (200 mg/day) is not clinically important in routine therapy desferrioxamine binds iron and reduces absorption (see Poisoning, below) tea (tannins) and bran reduce absorption. 

Cisplatin has also been shown to induce ROS in cultured proximal tubular cells and antioxidants such as green tea tannin can dose dependency protect against cisplatin-induced nephrotoxicity in vitro and in vivo [126]. Bragado and colleagues have recently demonstrated that cisplatin-induced apoptosis requires the onset of p53-mediated p38alpha MARK via the generation of reactive oxygen species [127]. 

YokozawaT, NakagawaT, Lee Kl, Cho EJ,Terasawa K, andTakeuchi S. Effects of green tea tannin on cisplatin-induced nephropathy in LLC-PK1 cells and rats.J Pharm Pharmacol 51 1325-1331,1999. 

The tea bush and in particular its young leaves contain a high concentration of polyphenols and oxidative enzymes, thus the young leaves are better for tea manufacture. Tea polyphenols, previously called tea tannins, are also known as tea flavonoids. Among the polyphenols in fresh tea leaves, catechins are the predominant form of polyphenols, which account for 12-24% of the dry weight. Besides catechins, flavonol, and their glycosides, anthocyanidin and leucoanthocyanidin, phenolic acids and depsides are also present. Their typical concentrations are shown in table 8.1. These phenolic compounds are directly or indirectly associated with the characteristics of tea, including its color, taste, and aroma. 

Black tea has been shown to reduce iron absorption, especially in individuals who have an increased risk of anemia (Disler et al. 1975 Merhav et al. 1985). The postulated mechanism of action is the formation of iron complexes with black tea tannins in the gut (South et al. 1997). However, in a review of clinical trials and epidemiological studies of black... 

Yokozawa, T. Chung, H.Y. He, L.Q. Oma, H. Effectiveness of green tea tannin on rats with chronic renal failure. Biosci. Biotech Biochem. 1996, 60,1000-1005. 

Black Tea. The freshly harvested leaves are spread out on mats and allowed to dry slowly and wither, after which they are mechanically rolled and broken to liberate the oxidase enzymes present in the cell sap and ensure their close contact with precursors. The rolled leaves are then fermented for several hours, usually in baskets or spread out under damp cloths. During this stage the colorless tea tannins are partially oxidized, changing to a reddish brown color, and some essential oil is formed. This primary oxidation gives to the leaves a very agreeable odor and color and determines the flavor quality, strength, body, and color of tea made from them. The process is stopped by firing at about 85°C. This induces a secondary oxidation, a reduction in moisture content to about 5% and the full development of the characteristic tea odor and color. The whole process demands skill and experience to achieve a consistent quality. 

Different sources of tannins have different effects on gas production and methane production, hi an in vitro study with three condensed tannins (quebracho, grape seed, and green tea tannins) and four hydrolysable tannins (tara, valonea, myrabolan, and... 

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