Green tea catechin, epigallocatechin-3-gallate (EGCG): Mechanisms, perspectives and clinical applications

Abstract

An expanding body of preclinical evidence suggests EGCG, the major catechin found in green tea (Camellia sinensis), has the potential to impact a variety of human diseases. Apparently, EGCG functions as a powerful antioxidant, preventing oxidative damage in healthy cells, but also as an antiangiogenic and antitumor agent and as a modulator of tumor cell response to chemotherapy. Much of the cancer chemopreventive properties of green tea are mediated by EGCG that induces apoptosis and promotes cell growth arrest by altering the expression of cell cycle regulatory proteins, activating killer caspases, and suppressing oncogenic transcription factors and pluripotency maintain factors. In vitro studies have demonstrated that EGCG blocks carcinogenesis by affecting a wide array of signal transduction pathways including JAK/STAT, MAPK, PI3K/AKT, Wnt and Notch. EGCG stimulates telomere fragmentation through inhibiting telomerase activity. Various clinical studies have revealed that treatment by EGCG inhibits tumor incidence and multiplicity in different organ sites such as liver, stomach, skin, lung, mammary gland and colon. Recent work demonstrated that EGCG reduced DNMTs, proteases, and DHFR activities, which would affect transcription of TSGs and protein synthesis. EGCG has great potential in cancer prevention because of it’s safety, low cost and bioavailability. In this review, we discuss its cancer preventive properties and it’s mechanism of action at numerous points regulating cancer cell growth, survival, angiogenesis and metastasis. Therefore, non-toxic natural agent could be useful either alone or in combination with conventional therapeutics for the prevention of tumor progression and/or treatment of human malignancies.

Opposite Structural Effects of Epigallocatechin-3-gallate and Dopamine Binding to α-Synuclein

“…Such inhibitors have attracted attention for the development of new drugs against amyloidoses 2,3 . A promising anti-amyloidogenic compound is the antioxidant molecule epigallocatechin-3-gallate (EGCG), the major green tea polyphenol which displays neuroprotective and anticancerogenic effects in cellular and animal models 4,5 . EGCG redirects AS aggregation into offpathway, non-toxic, SDS-resistant, spherical and nanostructured oligomers of ~20-nm diameter 6 .…”

Green Tea Catechins for Prostate Cancer Prevention: Present Achievements and Future Challenges

“…Along with enzymatic activities, different endogenous compounds like glutathione, plasma protein thiols and iron-binding proteins are needed to maintain the oxidative balance. Dietary components, like vitamins and polyphenols, also contribute in maintaining intracellular redox homeostasis [26,27]. An increasing numbers of studies have demonstrated that GTPs are strong antioxidant compounds [21,28], nonetheless GTPs are also able to exert pro-oxidant effects.…”

“…The antioxidant properties of the GTCs are due to the presence of both the phenolic groups and the galloyl moiety, that allow electron delocalization, and free radical quenching ability. Accordingly to their structural features, EGCG and ECG are, among the four most abundant GTCs, the strongest antioxidants [27,32]. However, GTCs may undergo auto-oxidation reactions, leading to the formation of catechin dimers and free radicals that may be responsible of the pro-oxidant action observed in vitro after polyphenols administration.…”

Natural Compounds May Open New Routes to Treatment of Amyloid Diseases

“…However, a widely recognized problem in the therapeutic application of EGCG is the large variability in the bioavailability of orally administered EGCG (reviewed in [108] and [112]). This is owing to its high sensitivity to oxidation, the tendency to conjugate to proteins in the digestive tract (e.g., casein), and rapid metabolism in the body.…”