The Studies on Bioenhancer Effect of Red Onions and Other Nutrients on the Absorption of Epigallocatechin Gallate from Green Tea Extract in Human Volunteers

Anup Kale1, Sonia Gawande1, Swati Kotwal1, Shrirang Netke2, Waheed Roomi2, Vadim Ivanov2, Aleksandra Niedzwiecki2 and Matthias Rath2
1 Post Graduate Department of Biochemistry, University of Nagpur, Nagpur, M.S. 440033, India
2 Dr Matthias Rath Institute of Cellular Research,1260 Memorex Drive, Santa Clara, CA 95050, US

Presented at: 2nd International Conference on Tumor Progression & Therapeutic Resistance, Boston, September 18-20, 2005

Published in: 2nd International Conference on Tumor Progression & Therapeutic Resistance Proceedings, page 89.

Abstract

Introduction:
Lower incidence of stomach cancer has been shown to be associated with consumption of high amounts of tea. In vitro and animal studies have also demonstrated the anti-cancer activity of green tea, black tea and their active constituents. In vitro studies in out laboratory showed significant anti-cancer activity against various cancer cell lines in vivo and in vitro with a nutrient mixture (EF) containing EGCG. However, laboratory determinations of plasma levels of EGCG after human consumption of green tea products have shown poor absorption of EGCG. Therefore, we sought to determine if EGCG absorption could be enhanced with red onion (quercetin) supplementation.

Objective:
We studied the effect of consumption of GTE alone and in combination with a mixture of nutrients (EF) containing

Methods and Materials:
Green Tea Extract (GTE) and GTE plus several nutrients (EF) and EF + onions were fed to five human subjects on different days and the plasma levels of (-)-epigallocatechin-3- gallate (EGCG) were determined at 0, 2, 4, 6 and 8 hrs.

Results:
The areas under absorption curve (AUC) determined over a period of 6 hr were 1323.80+ 355.01, 1502.28+341.23 and 1814.32+554.98 ng.h/ml for GTE, EF and EF+onion groups. Corresponding values for the three groups for 8 hr were 1784.08+56.06, 1971.53+566.50 and 2490.03+878.15 ng.h/ml in that order. The 6 hr AUCs for EF and EF +onion groups were significantly higher than that for GTE group, while AUC for 8 hr was significantly higher for EF group than the other two groups. The plasma Cmax values obtained at 4 hr were 348.4+76.6, 384.0+78.5 and 468.4+131.4 ng/ml in GTE, EF and EF+onion groups respectively. The values for EF and EF+onion groups were significantly higher than the value for GTE group. Half life (t 1/2) for elimination ranged from 3.32 to 4.02 h and did not differ significantly between various groups. Various parameters measured indicate that the absorption of EGCG from EF was higher than that from GTE. Feeding of onion along with EF further increased the absorption. The percent absorption of EGCG determined on the basis of 8 hr AUC was 113.12+5.59 for EF and 136.35+6.78 for EF+ onion group as compared to GTE group. The Value for EF+onion group was significantly higher than that for EF group.

Conclusion:
The results demonstrated that increasing the amount of quercetin given along with EGCG could increase absorption of EGG from the intestine. The ultimate objective of improving the absorption of EGCG is to enhance the anticancer action of EF. In vivo studies need ot be conducted to determine if the ingestion of onion or quercetin along with EF helps I combating cancer.

Click to enlarge