Studies on the effects of oral administration of nutrient mixture, quercetin and red onions on the bioavailability of epigallocatechin gallate from green tea extract

Kale A., Gawande S., Kotwal S., Netke S., Roomi W., Ivanov V., Niedzwiecki A., Rath M.
Phytotherapy Research 2010; 24(S1); S48-S55

Epigallocatechin gallate (EGCG), a main anticancer component in green tea, has a poor bioavailability in rats and humans due to oxidation, metabolism and its efflux. It was hypothesized that nutrients that address these problems might result in increased bioavailability.

Plasma concentrations of EGCG at various time intervals were determined to calculate and compare the pharmacokinetic parameters after oral administration of green tea extract (GTE) or GTE as a nutrient mixture (E) or E + quercetin (Q)/red onions. In rat studies, supplementation of GTE with other nutrients (E) or E + Q raised the plasma Cmax from 55.29 ± 1.70 to 61.94 ± 1.70 ng/mL and 94.44 ± 1.59 ng/mL, respectively. The corresponding t½ elimination was 2.04 ± 0.2 h, 3.63 ± 0.66 h and 2.28 ± 0.049 h. The AUC0-24h were 510.16 ± 9.88 for GTE, 601.72 ± 19.10 ng.h/mL for E and 794.08 ± 15.27 ng.h/mL (p 0.05) for E + Q. In human studies when GTE was fed as GTE or E or E + red onions, the Cmax values were 348.4 ± 76.6, 384.0 ± 78.5 ng/mL and 468.4 ± 131.4. AUC0-8h was 1784.1 ± 56.06 (GTE), 1971.5 ± 566.5 ng.h/mL (E) and 2490 ± 878.1 (E + Q), but the change in t½ elimination was not significant. In conclusion, it is possible to increase the bioavailability of EGCG by supplementing it with nutrients and quercetin.

Key Words:
(-)-epigallocatechin gallate, bioavailability, green tea extract, quercetin, red onions, bioenhancers

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