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.
Highlights
Cancer is a major public health problem in the world
We investigated the antiproliferative effects of 10 major green tea polyphenols using two human colorectal cancer cell lines, HCT-116 and SW-480, and observed that epigallocatechin gallate (EGCG) showed the most potent antiproliferative effects among the tested compounds
10 representative tea polyphenols were selected to evaluate their biological activity. Based on their chemical structures, they were separated into two groups, phenolic acids and flavonoids, the latter of which was separated into two subgroups, the flavan-3-ol unit group and the galloylated catechin group (Figure 1)
Summary
Cancer is a major public health problem in the world. One in four deaths in the United States is due to cancer [1]. The clinical management of cancer invariably involves diverse conventional modalities, including surgery, radiation, and chemotherapy [2,3]. Because of the complexity of human cancer, alternative management may be needed to improve the efficacy of therapeutic treatments and the quality of life of patients [4,5]. Cancer chemoprevention or treatment may combine natural products with chemotherapeutic agents to inhibit tumor development [6,7,8]. Botanicals contain bioactive constituents, including some with potential health benefits. Many herbal medicines possess antioxidant properties, which play an important role in therapeutics [9]
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