Oak Ellagitannins Suppress the Phosphorylation of the Epidermal Growth Factor Receptor in Human Colon Carcinoma Cells

Abstract

The ellagitannins castalagin and vescalagin, and the C-glycosides grandinin and roburin E as well as ellagic acid were found to potently inhibit the growth of human colon carcinoma cells (HT29) in vitro. In a cell-free system these compounds were identified as potent inhibitors of the protein tyrosine kinase activity of the epidermal growth factor receptor (EGFR) with IC 50 values in the low nanomolar range. To address the question of whether the interference with the activity of the isolated EGFR also plays a role within intact cells, effects on the phosphorylation status of the EGFR, as a measure for its activity, were determined in HT29 cells. As exemplified for castalagin and grandinin, both the nonglycosylated and the glycosylated ellagitannins effectively suppressed EGFR phosphorylation, but only at concentrations > or =10 microM, thus, in a concentration range where growth inhibition was observed. These results indicate that the suppression of EGFR-mediated signaling might contribute to the growth inhibitory effects of these compounds present in oak-matured wines and spirits such as whiskey. In contrast, despite substantial growth inhibitory properties, ellagic acid did not significantly affect EGFR phosphorylation in HT29 cells up to 100 microM.

Metabolites Are Key to Understanding Health Effects of Wine Polyphenolics

“…They can reduce cell proliferation of colon cancer cells, possibly by inhibiting activity of the epidermal growth factor receptor (52). Ellagitannins ingested by rats are rapidly metabolized in the stomach and metabolites do not appear to include ellagic acid (53).…”

Influence of Berry Polyphenols on Receptor Signaling and Cell-Death Pathways: Implications for Breast Cancer Prevention

“…There is clear evidence that many berry polyphenols inhibit the tyrosine kinase activity of EGFR and HER2 purified from the cell membrane. This also occurs in intact cells, albeit at considerably higher doses (Table 4) (37–38). However, evidence of whether these polyphenols inhibit the dimerization of GFRs is not known.…”

Development of a fractionation method for the detection and identification of oak ellagitannins in red wines

“…In the present study the procedure proposed by Lee and coworkers [25] for the identification of ellagic acid conjugates in grapes was modified and employed for the identification of oak ellagitannins in oak-matured red wines. The modifications carried out in the method allowed the obtaining of all the oak ellagitannins in the same fraction, isolated from other phenolic compounds.…”

“…The different fractions were then analysed by HPLC-DAD-MS (instruments and methods described in Section 2.3) and those with purities higher than 95% of one ellagitannin were gathered, concentrated under reduced pressure and freeze-dried. The identities of the ellagitannins were assigned from the data obtained in the HPLC-DAD-MS and in the 1 H and 13 C NMR analyses [2,21,24,25]. The final purities of the powders were determined from the results of the HPLC-DAD-MS analyses.…”