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| − | '''Caffeine''' is a crystalline xanthine alkaloid and a [[stimulant drug]]. It is found in seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants or as enhancing the reward memory of pollinators. It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush. Some other sources are guarana, guayusa and yerba maté.
| + | [[File:Caffeine structure.svg|thumb|Caffeine structure]] |
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| − | ===Ingredients Found In Tea===
| + | '''Caffeine''' is a crystalline xanthine alkaloid and a stimulant drug. It is found in seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants or as enhancing the reward memory of pollinators. It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush. Some other sources are guarana, guayusa and [[Yerba mate|yerba maté]]. |
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| − | Tea contains catechins, a type of antioxidant. In a freshly picked tea leaf, [[catechins]] can comprise up to 30% of the dry weight. Catechins are highest in concentration in [[white tea]] and [[green tea]], while [[black tea]] has substantially fewer due to its oxidative preparation. Research by the U.S. Department of Agriculture has suggested the levels of antioxidants in green and black tea do not differ greatly, as green tea has an oxygen radical absorbance capacity (ORAC) of 1253 and black tea an ORAC of 1128 (measured in μmol TE/100 g). [[Antioxidant]] content, measured by the lag time for oxidation of cholesterol, is improved by the cold water steeping of [[varieties of tea]].
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| − | Tea also contains [[L-theanine]], and the stimulant caffeine at about 3% of its dry weight, translating to between 30 mg and 90 mg per 8 oz (250 ml) cup depending on type, brand, and [[brewing method]].
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| − | Tea also contains small amounts of [[theobromine]] and [[theophylline]]. Due to modern environmental pollution, [[fluoride]] and [[aluminum]] have also been found to occur in tea, with certain types of brick tea made from old leaves and stems having the highest levels. This occurs due to the tea plant's high sensitivity to and absorption of environmental pollutants.
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| − | Although tea contains various types of [[polyphenols]] and [[tannin]], it does not contain tannic acid. [[Tannic acid]] is not an appropriate standard for any type of tannin analysis because of its poorly defined composition.
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| − | ==See also==
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| − | * [[Theanine]]
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| − | * [[Health effects of tea]]
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| − | ==External links==
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| − | * [http://teaadvisor.com/caffeine.html The Reason Why There Is No Consensus When It Comes To Caffeine Levels In Tea]
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| − | * [http://teaadvisor.com/forum/index.php/topic,136820.0.html Caffeine in Tea May Help Promote a Healthy Liver]
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| − | * [http://teaadvisor.com/forum/index.php/topic,136820.msg138391.html#msg138391 Drinking four cups of tea every day could help reduce fat in liver]
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| − | ==References==
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| | [[category:tea]] | | [[category:tea]] |
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| | [[de:Koffein]] | | [[de:Koffein]] |
Caffeine is a crystalline xanthine alkaloid and a stimulant drug. It is found in seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants or as enhancing the reward memory of pollinators. It is most commonly consumed by humans in infusions extracted from the seed of the coffee plant and the leaves of the tea bush. Some other sources are guarana, guayusa and yerba maté.
