Recent advances on tea polyphenols

Abstract

Over the past decade many scientific and medical studies have focused on green tea for its long-purported health benefits. There is convincing evidence that tea is a cup of life. It has multiple preventive and therapeutic effects. This review thus focuses on the recent advances of tea polyphenols and their applications in the prevention and treatment of human cancers. Of the various polyphenols in tea, (-)-Epigallocatechin-3-gallate (EGCG) is the most abundant, and active compound studied in tea research. EGCG inhibits several molecular targets to inhibit cancer initiation and modulates several essential survival pathways to block cancer progression. Herein, we describe the various mechanisms of action of EGCG and also discuss previous and current ongoing clinical trials of EGCG and green tea polyphenols in different cancer types.

Figure 1

Chemical structures of major green tea polyphenols: The polyphenols that exist in green tea are mainly (+)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), and (−)-epigallocatechin gallate (EGCG). EGCG is the most powerful and the most abundant of the major catechins found in green tea.

Figure 2

Chemical structures of EGCG analogues 5 and 7 differ in their number of hydroxyl groups; Peracetate-protected EGCG [Pro-EGCG (1)] is more stable and has improved potency over parental compound EGCG. EGCG analogs with fluoro or amino substitutions also inhibit tumor growth with similar potency to that of Pro-EGCG.

Figure 3

Mechanisms of action: EGCG modulates several key regulators of cell cycle progression, apoptosis, transcription factors, and various signaling pathways that are involved in tumor growth, angiogenesis and metastasis. Recent advances on tea polyphenols: chemistry, biology, molecular targets and application in cancer prevention and treatment