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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" 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 "
[Show abstract][Hide abstract] ABSTRACT: Products containing natural additives, including antioxidants, are usually perceived by the consumers as safer than those with synthetic ones. Natural antioxidants, besides preservative activity, may exert beneficial health effects. Interactions between antioxidants may significantly change their antioxidant activity, thus in designing functional foods or food/cosmetic ingredients, knowledge on the type of interactions could be useful. In the present study, the interactions between ascorbic acid (AA; vitamin C) and different black and green tea extracts, influencing their antioxidant activities, were investigated. The antioxidant activities of tea extracts and their mixtures with AA prepared in several different weight ratios were measured using the TEAC (Trolox Equivalent Antioxidant Capacity), DPPH (1,1-diphenyl-2-picrylhydrazyl) and FRAP (Ferric Reducing Antioxidant Power) methods. The type of interaction was determined by interaction indexes and isobolograms. It was found that the weight ratio of extracts to AA significantly influenced the antioxidant activity of a mixture and the type of interaction between these components. The weight ratio of tea extract to AA can cause the change of interaction, e.g. from antagonism to additivism or from additivism to synergism. The observed differences in the type of interactions were probably also a result of different extracts' polyphenol composition and content. The type of interaction may also be affected by the medium in which extracts and AA interact, especially its pH and the solvent used. To obtain the best antioxidant effect, all these factors should be taken into account during designing of a tea extract-AA mixture.
Full-text · Article · Jun 2015 · Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment
"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  , 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 . "
[Show abstract][Hide abstract] ABSTRACT: Sensitive to the massive diffusion of purported metabolic and cardiovascular positive effects of green tea and catechin-containing extracts, many consumers of cardiovascular drugs assume these products as a "natural" and presumably innocuous adjunctive way to increase their overall health. However, green tea may interfere with the oral bioavailability or activity of cardiovascular drugs by various mechanisms, potentially leading to reduced drug efficacy or increased drug toxicity. Available data about interactions between green tea and cardiovascular drugs in humans, updated in this review, are limited so far to warfarin, simvastatin and nadolol, and suggest that the average effects are mild to modest. Nevertheless, in cases of unexpected drug response or intolerance, it is warranted to consider a possible green tea-drug interaction, especially in people who assume large volumes of green tea and/or catechin-enriched products with the conviction that "more-is-better"
Full-text · Article · Oct 2014 · Current Pharmaceutical Design
"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. "
[Show abstract][Hide abstract] ABSTRACT: Background
Oxidative stress is involved in the pathogenesis of bone diseases such as osteoporosis, which has a high coincidence with fractures in elderly. Several studies showed positive effects of herbal bioactive substances on oxidative stress. This study analyses the effect of green tea extract (GTE) Sunphenon 90LB on primary human osteoblasts differentiation and viability during H2O2-induced oxidative stress. Moreover, it was analyzed, whether GTE acts during the HO-1 signaling pathway.
Human osteoblasts were isolated from femoral heads of patients undergoing total hip replacement. Beneficial effects of GTE on osteoblasts were examined in a dose- and time-dependent manner. Furthermore, GTE was given before, simultaneous with and after induction of oxidative stress with 1 mM H2O2 to simulate prophylactic, acute and therapeutic use, respectively. Cell damage was measured by LDH leakage and cell viability by MTT assay. Flow cytometry was applied to measure formation of Reactive Oxygen Species by using 2`7`-dichlorofluorescein-diacetate. The formation of Extracellular Matrix after differentiation with GTE supplementation during oxidative stress was visualized with von Kossa and Alizarin Red staining. Last one was additionally photometrically quantified. To assess the effects of H2O2 and GTE on the osteogenic genes, RT-PCR was performed. To evaluate the intramolecular influence of GTE after the stimulation the protein levels of HO-1 were analyzed.
Stimulation of primary human osteoblasts with low doses of GTE during oxidative stress over 21 days improved mineralization. Furthermore, GTE supplementation in combination with H2O2 leads to a higher gene expression of osteocalcin and collagen1α1 during osteoblasts differentiation. Both are important for bone quality. Pre-incubation, co-incubation and post-incubation of osteoblasts with high doses of GTE protect the osteoblasts against acute oxidative stress as shown by increased cell viability, decreased LDH leakage, and reduced production of intracellular free radicals. Functional analysis revealed an increased HO-1 protein synthesis after stimulation with GTE.
Incubation of human primary osteoblasts with GTE significantly reduces oxidative stress and improves cell viability. GTE also has a beneficial effect on ECM production which might improve the bone quality. Our findings suggest that dietary supplementation of GTE might reduce inflammatory events in bone-associated diseases such as osteoporosis.
Full-text · Article · May 2014 · Journal of Inflammation