Epicatechin Gallate (ECG · Green Tea Catechin · Antimicrobial · Antioxidant)

Compound	Epicatechin Gallate (ECG; (-)-Epicatechin-3-O-Gallate; (-)-ECG)
Chemical class	Polyphenol — Flavan-3-ol Gallate (epicatechin with galloyl ester at C-3; second-most abundant green tea catechin gallate)
CAS	1257-08-5
Primary source	Camellia sinensis (green tea leaves — 10–15% of total catechin content in green tea)
Key applications	Antimicrobial (MRSA); antioxidant; lipid-lowering; anti-inflammatory
Claim strength	Moderate
Typical form	EGCG 50% Green Tea Extract (ECG co-delivered at ~10-15% of catechin fraction); Green Tea Catechin Concentrate
Buy from Herbuno	EGCG 50% Powder (Green Tea Extract) | Standardized Camellia sinensis → Green Tea Liquid Extract (Water Soluble) - Camellia sinensis →

Name origin: ECG stands for Epicatechin-3-Gallate — epicatechin esterified with gallic acid at C-3 of the flavan-3-ol C-ring. It shares the catechol B-ring (3′,4′-dihydroxy) of epicatechin but adds galloyl ester character from gallic acid — increasing astringency, radical scavenging capacity, and antimicrobial activity relative to the parent epicatechin. Traditional use: ECG does not have independent traditional medicinal use — it is a constituent of green tea, where it occurs alongside EGCG as a gallated catechin. The medicinal tradition belongs to green tea as a whole. In analytical chemistry, ECG was resolved from EGCG in the early 20th century as part of systematic tea catechin fractionation work. Research trajectory: ECG has attracted specific research attention for its antimicrobial profile — particularly against methicillin-resistant Staphylococcus aureus (MRSA), where ECG shows superior activity to EGCG in some MIC assays — and for its cholesterol-lowering activity via bile acid binding and HMG-CoA reductase modulation. Its bioavailability is comparable to EGCG (low, ~1–3% oral), following the same absorption bottlenecks. Commercial source: ECG is co-delivered in EGCG 50% Green Tea Extract from Herbuno at approximately 10–15% of the catechin fraction — practical access without requiring isolated ECG preparations.

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Evidence for ECG Applications

Antimicrobial (MRSA and antibiotic resistance): ECG demonstrates potent activity against MRSA (methicillin-resistant S. aureus) at MIC values of 32–128 μg/mL in broth dilution assays. More importantly, ECG synergises with beta-lactam antibiotics against MRSA — reducing the MIC of oxacillin by 8–16-fold, effectively resensitising resistant strains. The mechanism involves disruption of PBP2a (the alternative penicillin-binding protein that mediates beta-lactam resistance in MRSA) via membrane fluidisation and altered transpeptidation. This synergistic anti-MRSA mechanism is one of the most pharmacologically significant antimicrobial properties attributed to any single dietary catechin. Claim strength: Moderate (in vitro, animal confirmatory).

Antioxidant: ECG's catechol B-ring and galloyl ester system confer high DPPH, ABTS, and superoxide scavenging activity — somewhat lower than EGCG's pyrogallol B-ring equivalent but still among the highest for dietary polyphenols. Fe³⁺ reduction (FRAP) capacity is high due to the galloyl moiety's electron-donating capacity. Claim strength: Moderate.

Lipid-lowering: ECG binds bile acids in the intestinal lumen (via galloyl group-bile acid interaction), reducing bile acid reabsorption and increasing hepatic cholesterol conversion to replace lost bile acid — a mechanism equivalent to cholestyramine resin but at lower potency. In hypercholesterolaemic animals, ECG reduces total cholesterol and LDL. Human evidence is indirect (green tea consumption studies). Claim strength: Moderate (animal/mechanistic); Emerging (isolated human).

Anti-inflammatory: NF-κB inhibition and COX-2 suppression are documented for ECG, with potency intermediate between epicatechin and EGCG. Mast cell degranulation inhibition (IgE-mediated histamine release) positions ECG in anti-allergic formulation context. Claim strength: Moderate.

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Dosage & Formulator Specification

No isolated ECG human dosing data exist. ECG is studied as a component of green tea catechin preparations rather than in isolation. In typical green tea extract preparations, ECG represents 10–15% of total catechin content; at a serving of 400 mg EGCG 50% extract (providing ~200 mg EGCG), approximately 30–50 mg ECG is co-delivered.

For antimicrobial applications targeting ECG's MRSA synergy mechanism, concentrations used in in vitro studies (32–256 μg/mL) are not achievable systemically via oral supplementation. Topical applications — wound care, skin antiseptic preparations containing green tea catechin concentrates — can achieve relevant ECG concentrations at the surface level. Clinical translation of the MRSA synergy requires pharmaceutical development, not standard supplement formulation.

ECG's bioavailability follows EGCG's constraints: fasting-state administration, avoidance of milk proteins, and phospholipid complexation all improve absorption. Stability in aqueous formulations requires the same pH 4–6 and antioxidant protection as EGCG. The galloyl ester bond is susceptible to hydrolysis at alkaline pH and elevated temperature — generating epicatechin + gallic acid, both of which retain bioactivity.

No specific drug interactions are documented for isolated ECG. As a green tea catechin, it shares the class-level considerations: iron absorption interference, weak CYP1A2 modulation, and potential additive effects with anticoagulants at high doses.

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Frequently Asked Questions — ECG

How does ECG differ from EGCG structurally and pharmacologically?
ECG (epicatechin-3-gallate) has a catechol B-ring (3′,4′-dihydroxy); EGCG (epigallocatechin-3-gallate) has a pyrogallol B-ring (3′,4′,5′-trihydroxy). This additional hydroxyl in EGCG's B-ring gives EGCG higher radical scavenging capacity and broader enzyme inhibition. ECG's catechol ring is associated with its specific MRSA beta-lactam synergy mechanism, which EGCG shares only partially. ECG is the less abundant gallated catechin (10–15% vs EGCG's 50–70% of green tea total catechins).

What makes ECG useful for antibiotic resistance research?
ECG disrupts the cell membrane of MRSA and interferes with PBP2a (penicillin-binding protein 2a) — the altered transpeptidase that makes MRSA resistant to beta-lactam antibiotics. By fluidising the bacterial membrane, ECG partially restores PBP2a's susceptibility to beta-lactam binding, resensitising MRSA to oxacillin and methicillin. This beta-lactam resensitisation mechanism (rather than direct bactericidal activity) makes ECG a pharmaceutical candidate for combination therapy — not a standalone antibiotic supplement ingredient.

Is ECG standardised in commercial green tea extracts?
Most commercial green tea extracts standardise to EGCG content, with the total catechin fraction (EGC + EGCG + ECG + EC + catechin) reflected in the total polyphenol specification. ECG is not separately specified in most commercial CoAs. HPLC catechin profiling can quantify ECG individually; specialty catechin concentrate preparations with defined ECG content are available from fractionation specialists. EGCG 50% from Herbuno delivers ECG as a co-catechin at approximately 10–15% of the catechin fraction.

Does the galloyl group in ECG affect gut microbiome differently than non-gallated catechins?
Yes — gallated catechins (ECG, EGCG) are less efficiently absorbed in the small intestine than non-gallated catechins (epicatechin, catechin), meaning more reaches the colon for microbial transformation. Colonic bacteria cleave the galloyl ester, producing epicatechin + gallic acid, both of which are absorbed from the colon. The galloyl group also has direct antimicrobial activity against some gut pathogens, potentially contributing to prebiotic-type selective microbiome effects. Non-gallated catechins tend to be better absorbed earlier in the GI tract.

Related compounds: EGCG, Epicatechin, Gallocatechin Gallate, Catechin

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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