Biomarkers of antioxidant status following ingestion of green teas at different polyphenol concentrations and antioxidant capacity in human volunteers.

In a randomized cross-over study, 15 healthy volunteers consumed 500 mL of green tea (GTFT) with different solid contents (1.4, 1.6, 1.8 and 2.0 g/L) to induce a dose-response effect on plasma antioxidant capacity. Ingestion of GTFT 2.0 g/L significantly increased plasma reducing power (ferric reducing antioxidant power, FRAP) at 1 h (+2.9%; p<0.01), 2 h (+2.5%; p<0.05) and 4 h (+3.6%; p<0.01). GTFT 1.8 g/L showed statistical significance at 1 h (+4.3%; p<0.01) and 2 h (+4.4%; p<0.01), whereas GTFT 1.6 g/L was effective only at 1 h (+2.9%; p<0.01) and GTFT 1.4 g/L did not induce any changes. The maximum peak of increase in plasma FRAP for different GTFTs was clearly correlated with in vitro FRAP (R=0.778). GTFT 2.0 g/L significantly increased plasma antioxidant potential (total radical-trapping antioxidant parameter) at 1 h (+8.4%; p<0.01), 2 h (+4.4%; p<0.05) and 4 h (+5.9%; p<0.01). The effect of GTFT 1.8 g/L was evident at 1 h (+5.2%; p<0.05) and 2 h (+4.6%; p<0.05) but not at 4 h. No changes in plasma total radical-trapping antioxidant parameter were detected for GTFT at 1.6 and 1.4 g/L. An evidence for a linear correlation between GTFT antioxidant content and the extent of the antioxidant effect in vivo has been provided.

Bioavailability of C-linked dihydrochalcone and flavanone glucosides in humans following ingestion of unfermented and fermented rooibos teas.

High-performance liquid chromatography-mass spectrometry (HPLC-MS(n)) detected aspalathin and nothofagin, C-glycosides of apigenin and luteolin, and four eriodictyol-C-glycoside isomers in unfermented and fermented rooibos teas. The fermented drink contained 10-fold higher levels of aspalathin and nothofagin and a 4-fold lower eriodictyol-C-glycoside content than the fermented tea. The total flavonoid contents in 500 mL servings of the teas were 84 (fermented) and 159 mumol (unfermented). Following the ingestion of 500 mL of the teas by 10 volunteers, 0-24 h urine and plasma samples were collected for analysis. HPLC-MS(n) identified eight metabolites in urine. These were O-linked methyl, sulfate, and glucuronide metabolites of aspalathin and an eriodictyol-O-sulfate. The main compound excreted was an O-methyl-aspalathin-O-glucuronide (229 nmol) following ingestion of the unfermented drink and eriodictyol-O-sulfate (68 nmol) after ingestion of the fermented beverage. The overall metabolite levels excreted were 82 and 352 nmol, accounting for 0.09 and 0.22% of the flavonoids in the fermented and unfermented drinks, respectively. Most of the aspalathin metabolites were excreted within 5 h of tea consumption, suggesting absorption in the small intestine. Urinary excretion of the eriodictyol-O-sulfate occurred mainly during the 5-12 h collection period, indicative of absorption in the large intestine. Despite exhaustive searches, no flavonoid metabolites were detected in plasma.

Green tea, white tea, and Pelargonium purpureum increase the antioxidant capacity of plasma and some organs in mice.

OBJECTIVE: We tested in mice the hypothesis that ingestion of infusions of green tea, white tea, or the aromatic plant Pelargonium purpureum increases total antioxidant capacity (TAC) of plasma and organs. METHODS: Twenty-five mice were randomly assigned to five groups, each of which received by gavage 0.1 mL of infusion from green tea, white tea, or P. purpureum (8 g/100 mL of water) or catechin (0.01 g/100 mL) or water for 5 consecutive days. On the fifth day the animals were euthanized. Blood was taken by heart puncture and the heart, lungs, liver, spleen, kidney, and brain were removed. TAC was measured in plasma and in all organ homogenates with the ferric reducing antioxidant power assay and in selected organ homogenates by the total radical-trapping antioxidant parameter assay. RESULTS: Green tea and P. purpureum increased TAC in the plasma and lungs, whereas green tea, white tea, and catechin increased TAC in heart homogenates. No effect was observed on the liver, brain, spleen, and kidney homogenates in comparison with the water control with the ferric reducing antioxidant power assay or the total radical-trapping antioxidant parameter assay. CONCLUSION: These results suggest that green tea, white tea, and P. purpureum exhibit antioxidant effects in vivo that may be observed not only in plasma but also in some organs.