Catechin and Caffeine Content of Green Tea Dietary Supplements and Correlation with Antioxidant Capacity

Center for Human Nutrition, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA.
Journal of Agricultural and Food Chemistry (Impact Factor: 2.91). 04/2006; 54(5):1599-603. DOI: 10.1021/jf052857r
Source: PubMed


The health benefits associated with tea consumption have resulted in the wide inclusion of green tea extracts in botanical dietary supplements, which are widely consumed as adjuvants for complementary and alternative medicines. Tea contains polyphenols such as catechins or flavan-3-ols including epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate (EGCG), as well as the alkaloid, caffeine. Polyphenols are antioxidants, and EGCG, due to its high levels, is widely accepted as the major antioxidant in green tea. Therefore, commercial green tea dietary supplements (GTDS) may be chemically standardized to EGCG levels and/or biologically standardized to antioxidant capacity. However, label claims on GTDS may not correlate with actual phytochemical content or antioxidant capacity nor provide information about the presence and levels of caffeine. In the current study, 19 commonly available GTDS were evaluated for catechin and caffeine content (using high-performance liquid chromatography) and for antioxidative activity [using trolox equivalent antioxidant capacity (TEAC) and oxygen radical antioxidant capacity (ORAC) assays]. Product labels varied in the information provided and were inconsistent with actual phytochemical contents. Only seven of the GTDS studied made label claims of caffeine content, 11 made claims of EGCG content, and five specified total polyphenol content. Caffeine, EGCG, and total polyphenol contents in the GTDS varied from 28 to 183, 12-143, and 14-36% tablet or capsule weight, respectively. TEAC and ORAC values for GTDS ranged from 187 to 15340 and from 166 to 13690 mumol Trolox/g for tablet or capsule, respectively. The antioxidant activities for GTDS determined by TEAC and ORAC were well-correlated with each other and with the total polyphenol content. Reliable labeling information and standardized manufacturing practices, based on both chemical standardization and biological assays, are recommended for the quality control of botanical dietary supplements.

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Available from: David Heber, Dec 18, 2014
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    • " assay . The antioxidant activities of the extracts were dependent on their total polyphenol content . The literature data on the antioxidant activity of tea extracts refer mostly to green tea . It was reported that the antioxidant activity of water GTE determined using the TEAC assay may range from 1 . 86 to 12 . 62 mmol trolox g – 1 of extract ( Seeram et al . 2006 ) . The IC 50 value obtained in the DPPH method may range from about 1 . 7 to 40 µg ml – 1 ( Saito et al . 2007 ; Unachukwu et al . 2010 ; Chen et al . 2012 ) . The TEAC or IC 50 values depend on type or subtype of green tea and the preparation method of tea samples ( Unachukwu et al . 2010 ) . Fermentation of tea leaves results in the "
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    • "Recently, this typically oriental infusion has gained wide use in western countries not only as a traditional tea infusion but also as industrialized beverages and dietary supplements. Commercially available green teas and green tea products widely differ in the content of catechins (the main supposed " active principles " of green tea) and other components [7] [8], some of which may interact pharmacologically with cardiovascular drugs. This review is aimed to disseminate updated information about potentially relevant interactions between green teas (or green tea products) and drugs utilized in CVD prevention and therapy . "
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    • "Especially green tea and its polyphenolic compounds - catechins - are known to prevent oxidative stress [15-17]. The major green tea catechins are epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG) [18-20]. In our study we used the innovated decaffeinated Green Tea Extract Sunphenon LG90 (GTE) containing more than 80% polyphenols, thereof more than 80% catechins, more than 40% epigallocatechin and less than 1% caffeine. "
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