Epigallocatechin Gallate (EGCG) is the most effective cancer chemopreventive polyphenol in green tea - PubMed (original) (raw)

Comparative Study

. 2012 Nov 8;4(11):1679-91.

doi: 10.3390/nu4111679.

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Comparative Study

Epigallocatechin Gallate (EGCG) is the most effective cancer chemopreventive polyphenol in green tea

Guang-Jian Du et al. Nutrients. 2012.

Abstract

Green tea is a popular drink consumed daily by millions of people around the world. Previous studies have shown that some polyphenol compounds from green tea possess anticancer activities. However, systemic evaluation was limited. In this study, we determined the cancer chemopreventive potentials of 10 representative polyphenols (caffeic acid, CA; gallic acid, GA; catechin, C; epicatechin, EC; gallocatechin, GC; catechin gallate, CG; gallocatechin gallate, GCG; epicatechin gallate, ECG; epigallocatechin, EGC; and epigallocatechin gallate, EGCG), and explored their structure-activity relationship. The effect of the 10 polyphenol compounds on the proliferation of HCT-116 and SW-480 human colorectal cancer cells was evaluated using an MTS assay. Cell cycle distribution and apoptotic effects were analyzed by flow cytometry after staining with propidium iodide (PI)/RNase or annexin V/PI. Among the 10 polyphenols, EGCG showed the most potent antiproliferative effects, and significantly induced cell cycle arrest in the G1 phase and cell apoptosis. When the relationship between chemical structure and anticancer activity was examined, C and EC did not show antiproliferative effects, and GA showed some antiproliferative effects. When C and EC esterified with GA to produce CG and ECG, the antiproliferative effects were increased significantly. A similar relationship was found between EGC and EGCG. The gallic acid group significantly enhanced catechin's anticancer potential. This property could be utilized in future semi-synthesis of flavonoid derivatives to develop novel anticancer agents.

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Figures

Figure 1

Figure 1

Chemical structures and classifications of tested tea polyphenols.

Figure 2

Figure 2

Effects of tea polyphenols on proliferation of human colorectal cancer cells. Cell lines (A) HCT-116, and (B) SW-480 were employed to evaluate the antiproliferative effects of selected compounds. Cells were treated with 10–300 μM of tea polyphenol compounds for 48 h, and cell proliferation was assayed by MTS method. Results were normalized to each control in percentage and expressed as average ± S.E. of triplicate experiments (solvent vehicle set at 100%).

Figure 3

Figure 3

Effects of EGCG on HCT-116 cell cycle. HCT-116 cells were treated with 10–50 μM of EGCG for 48 h, and then cell cycle profile was determined using flow cytometry after staining with PI/RNase. (A) Representative histograms of DNA content in each experimental group. (B) Percentage of each cell cycle phase with various treatments or with control. Data are presented as the mean ± S.E. of triplicate experiments. * p < 0.05; ** p < 0.01 vs. control.

Figure 4

Figure 4

Effects of EGCG on HCT-116 cell apoptosis. HCT-116 cells were treated with 20–100 µM of EGCG for 48 h. Apoptosis was quantified using flow cytometry after staining with annexin V/PI. (A) Representative scatter plots of PI (_y_-axis) vs. annexin V (_x_-axis). (B) Percentage of viable, early and late apoptotic cells. Data are presented as the mean ± S.E. of triplicate experiments. * p < 0.05; ** p < 0.01 vs. control.

Figure 5

Figure 5

The three-dimensional (3D) structures of galloylated catechins. Molecular modeling of EGCG and other galloylated catechins was generated by MM2 force field method. (Left panel) Taking EGCG as a model structure, the three aromatic rings are assigned as rings A, B and D, while the pyran ring is assigned C. (Right panel) MM2 optimized 3D structures of CG, GCG, ECG and EGCG are shown.

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