EGCG

EGCG, or (-)-epigallocatechin-3-gallate, is a type of catechin and a polyphenolic compound. It is the most abundant and biologically active catechin present in green tea (Camellia sinensis), formed as the galloylated ester of epigallocatechin. EGCG is a major contributor to the antioxidant properties attributed to green tea.

Green tea is the primary source of EGCG; its content varies with tea cultivar, growing conditions, and processing. EGCG levels are higher in green tea than in black tea, where oxidation converts catechins into other compounds. In addition to beverages, EGCG is frequently extracted for use in dietary supplements, beverages, and cosmetics.

Biological activity and mechanisms: EGCG is a potent antioxidant and free radical scavenger. It can modulate signaling pathways and gene expression, including NF-κB and MAPK pathways, and inhibit enzymes such as lipoxygenase and cyclooxygenase. In laboratory studies, EGCG has shown anti-inflammatory, anti-carcinogenic, and anti-angiogenic effects. In humans, evidence from observational and interventional studies is mixed and does not establish clear disease-preventive benefits.

Bioavailability and metabolism: Oral bioavailability of EGCG is relatively limited. After ingestion, it undergoes metabolism to glucuronide and sulfate conjugates, with additional transformation by intestinal microflora. Absorption can be influenced by food, other polyphenols, and the form in which EGCG is consumed.

Safety: In typical dietary amounts from green tea, EGCG is generally regarded as safe for most individuals. High-dose green tea extracts or supplements have been linked to rare cases of liver injury. Possible interactions include reduced iron absorption and interactions with anticoagulants or certain medications. People with liver disease, pregnancy, or those taking specific drugs should consult a healthcare professional before high-dose supplementation.