Epigallocatechin-3-gallate (EGCG): chemical and biomedical perspectives

Abstract

The compound (-)-epigallocatechin-3-gallate (EGCG) is the major catechin found in green tea [Camellia sinensis L. Ktze. (Theaceae)]. This polyphenolic compound and several related catechins are believed to be responsible for the health benefits associated with the consumption of green tea. The potential health benefits ascribed to green tea and EGCG include antioxidant effects, cancer chemoprevention, improving cardiovascular health, enhancing weight loss, protecting the skin from the damage caused by ionizing radiation, and others. The compound EGCG has been shown to regulate dozens of disease-specific molecular targets. Many of these molecular targets are only affected by concentrations of EGCG that are far above the levels achieved by either drinking green tea or consuming moderate doses of green tea extract-based dietary supplements. In spite of this, well-designed double-blinded controlled clinical studies have recently demonstrated the efficacy of green tea extracts and purified EGCG products in patients. Therefore, this review highlights results from what the authors believe to be some of the most clinically significant recent studies and describes current developments in the stereoselective total synthesis of EGCG.

Scheme 1

Reagents and conditions: i) Pd-H₂/EtOH, then NaBH₄/EtOH; ii) SOCl₂, then 1,8-DBU/CH₂Cl₂, reflux; iii) AD-mix-α, ButOH/H₂O (1:1 v/v), MeSO₂NH₂, 0° C; iv) 3M HCl, MeOH/H₂O (3:1 v/v).

Scheme 2

Reagents and conditions: i) H₂SO₄(SiO₂)/CH₂Cl₂/CS₂/rt; ii) TBDMSCl/imidazole/DMF, rt; iii) AD-mix-α/CH₃SO₂NH₂/H₂O/t-BuOH, 0° C; iv) TBAF/THF, rt; v) CH(OEt)₃/PPTS/CH₂Cl₂, rt; vi) Dess-Martin periodinane/CH₂Cl₂, rt; vii) L-selectride/THF, -78°C→ rt; viii) 3,4,5-tris(benzyloxy)benzoyl chloride/DMAP/CH₂Cl₂, rt; ix) H₂/Pd(OH)₂/MeOH/THF, rt.

Scheme 3

Reagents and conditions: i) NBS/AIBN in CCl₄, reflux; ii) NaB³H₄/MeOH, rt, then NaBH₄/MeOH