Gallocatechin Gallate (GCG · Flavan-3-ol Gallate · Lipid Metabolism · Immunomodulatory)

Compound	(+)-Gallocatechin-3-Gallate (GCG; Gallocatechin Gallate; (+)-GCG)
Chemical class	Polyphenol — Flavan-3-ol Gallate (pyrogallol B-ring catechin with galloyl ester; C-3 epimer of EGCG)
CAS	4233-96-9
Primary source	Camellia sinensis (green and white tea leaves — minor gallated catechin, ~3-6% of total catechins)
Key applications	Lipid metabolism; immunomodulatory; antioxidant; antimicrobial
Claim strength	Moderate
Typical form	Green Tea Catechin Concentrate (GCG as minor fraction); EGCG 50% Green Tea Extract (GCG co-delivered at low %)
Buy from Herbuno	EGCG 50% Powder (Green Tea Extract) | Standardized Camellia sinensis → Green Tea Liquid Extract (Water Soluble) - Camellia sinensis →

Name origin: Gallocatechin Gallate (GCG) is the C-3 epimer of EGCG — sharing EGCG's pyrogallol B-ring and galloyl ester at C-3 but differing in the stereochemistry at C-3 of the flavan-3-ol C-ring. The (+) prefix denotes the 2R,3S configuration versus EGCG's (-) 2R,3R configuration. This seemingly minor stereochemical difference produces significant differences in enzyme binding affinity, receptor selectivity, and biological activity between GCG and EGCG. Traditional use: GCG has no independent traditional medicinal use — it is among the minor catechins of green tea, consistently present at lower concentrations than EGCG, ECG, EGC, epicatechin, and catechin. Its pharmacological distinctiveness from EGCG was not appreciated until modern receptor pharmacology methods enabled stereochemistry-specific characterisation. Research trajectory: GCG's most studied biological distinctions from EGCG relate to immunomodulatory activity (including effects on mast cells and allergic signalling) and lipid metabolism modulation. Its lower abundance in green tea means it is rarely studied in clinical settings independently; research typically uses synthetic GCG or fractionated preparations. Commercial source: GCG is co-delivered as a minor catechin in EGCG 50% Green Tea Extract and Green Tea Liquid Extract from Herbuno. Isolated GCG is available from specialty tea fractionation suppliers for research purposes.

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Evidence for GCG Applications

Lipid metabolism: GCG inhibits pancreatic lipase activity at concentrations comparable to EGCG, reducing dietary fat hydrolysis and absorption in in vitro and animal assays. In high-fat diet rodent studies, GCG reduces adipose tissue accumulation and plasma triglycerides. The galloyl group contributes to lipase inhibition via substrate-competitive binding at the catalytic site. Claim strength: Moderate (animal/biochemical).

Immunomodulatory activity: GCG has demonstrated distinct immunomodulatory properties relative to EGCG in mast cell degranulation models — inhibiting IgE-mediated histamine release and PGD₂ production via FcεRI receptor pathway suppression. The stereochemical difference from EGCG affects IgE receptor interaction geometry, giving GCG a potentially differentiated anti-allergic profile. Claim strength: Emerging.

Antioxidant: GCG's pyrogallol B-ring + galloyl ester combination gives antioxidant capacity essentially equivalent to EGCG in radical scavenging assays. In metal chelation assays, GCG shows slightly different metal ion selectivity than EGCG due to its C-3 stereochemical effect on the galloyl group's spatial orientation. Claim strength: Moderate.

Antimicrobial: GCG demonstrates antimicrobial activity against S. aureus (including MRSA), E. coli, and Candida albicans at MIC values similar to EGCG and ECG. The mechanism involves membrane disruption consistent with the gallated catechin class. Claim strength: Moderate (in vitro).

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Dosage & Formulator Specification

No isolated GCG human dosing data exist. GCG represents 3–6% of total green tea catechins — substantially less than EGCG (50–70%). At a standard serving of 400 mg EGCG 50% Green Tea Extract (providing ~200 mg EGCG), approximately 10–20 mg GCG is co-delivered.

GCG is not commercially standardised as an individual catechin in routine green tea extract specifications. Full HPLC catechin profiling distinguishing GCG from EGCG requires stereochemistry-aware analytical methods (chiral HPLC or baseline resolution on reversed-phase methods). Most routine HPLC catechin assays group EGCG and GCG into a single peak due to very similar retention times, potentially underreporting GCG as EGCG in some supplier CoAs.

Stability of GCG in formulations is similar to EGCG — the pyrogallol B-ring is susceptible to oxidation; galloyl ester hydrolysis at alkaline pH generates gallocatechin + gallic acid. pH 4–6, nitrogen atmosphere, and ascorbic acid co-formulation are standard protective measures. Shelf stability in dry extract form is good at ambient temperature and controlled humidity.

No significant drug interactions are documented for GCG specifically. Class considerations for gallated catechins apply: iron chelation, weak CYP modulation at high doses, potential additive effects with antiplatelet agents.

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Frequently Asked Questions — GCG

What is the stereochemical difference between GCG and EGCG and why does it matter?
EGCG is (-)-epigallocatechin-3-gallate (2R,3R configuration at C-2 and C-3); GCG is (+)-gallocatechin-3-gallate (2R,3S configuration). The C-3 stereochemical difference changes the relative orientation of the galloyl ester and the C-ring hydroxyl in 3D space. This affects receptor binding — particularly for enzymes with stereospecific active sites (lipase, some kinases) — producing different IC₅₀ profiles despite near-identical molecular formulae. In NMR and X-ray crystallography, the two compounds show distinct spatial conformations of the galloyl group.

Is GCG present in decaffeinated green tea extract?
Yes — the decaffeination process (supercritical CO₂, ethyl acetate, or hot water extraction) removes caffeine but generally preserves the catechin fraction including GCG. The relative catechin proportions may shift slightly depending on the decaffeination method, but GCG as a minor catechin is typically retained. Decaffeinated green tea extract maintains its antioxidant, anti-inflammatory, and metabolic catechin activities, including the contribution of GCG.

How does GCG compare to EGCG for anti-allergic / mast cell applications?
GCG has demonstrated differentiated mast cell degranulation inhibition in some in vitro studies — showing greater FcεRI (high-affinity IgE receptor) pathway suppression than EGCG at equivalent concentrations in certain assay conditions. This stereochemistry-specific anti-allergic differentiation is pharmacologically interesting but has not been studied in clinical allergy trials. Both EGCG and GCG inhibit mast cell degranulation; GCG's potential superiority for specific IgE-mediated allergic signalling steps requires validation in human models.

Why are EGCG and GCG sometimes reported as a combined peak in catechin HPLC analysis?
GCG and EGCG have very similar chromatographic properties on standard reversed-phase HPLC columns (C18) due to their near-identical molecular structures. Some analytical methods do not achieve baseline separation between the two stereoisomers, reporting them as a combined EGCG/GCG peak. This means commercial green tea extract CoAs reporting "EGCG content" by standard HPLC may include GCG in the reported value. Chiral HPLC or optimised gradient methods are required for definitive GCG vs EGCG quantification in research-grade characterisation.

Related compounds: EGCG, Epicatechin Gallate, Gallocatechin, 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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