Named Bioactive Compounds · Compound
Gallic acid
Strong Evidencephenolic_acid
Hermetica Superfood Encyclopedia
Gallic acid is a phenolic compound found in green tea, grapes, and oak bark that exhibits antioxidant and anti-inflammatory properties. It works primarily through scavenging free radicals and inhibiting inflammatory enzymes like cyclooxygenase and lipoxygenase.
Gallic acid (3,4,5-trihydroxybenzoic acid) is a naturally occurring polyphenolic compound found in plants such as gallnuts from oak trees, tea leaves, grapes, and carob. It's produced industrially through enzymatic hydrolysis of tannic acid using tannase enzymes, or extracted via maceration with methanol-water mixtures followed by liquid-liquid extraction.
Clinical evidence for isolated gallic acid is limited, with most data from small-scale trials. A 2018 RCT (PMID: 29438460) showed topical 2% gallic acid matched hydroquinone for melasma treatment, while a 2021 study (PMID: 34684561) demonstrated metabolic benefits in diabetes patients. A meta-analysis (PMID: 33667028) of gallic acid-rich pomegranate extracts found modest cardiovascular effects.
Oral: 100 mg/day pure powder for metabolic effects; 250-500 mg/day of extracts standardized to 10-20% gallic acid equivalents for cardiovascular benefits. Topical: 2% cream applied twice daily for skin conditions. No established RDA; doses above 500 mg/day remain untested in humans. Consult a healthcare provider before starting any new supplement.
Gallic acid (3,4,5-trihydroxybenzoic acid, C₇H₆O₅, MW 170.12 g/mol) is a naturally occurring polyphenolic compound, not a food per se, so it lacks conventional macronutrient or micronutrient profiles. Key details: • Classification: Low-molecular-weight phenolic acid belonging to the hydroxybenzoic acid subclass of polyphenols. • Natural concentrations in food sources: tea leaves (0.5–4.5 g/kg dry weight), gallnuts (50–70% by weight as tannic acid/gallotannins which hydrolyze to gallic acid), pomegranate (20–60 mg/100 mL juice), grapes and wine (10–50 mg/L in red wine), berries such as blackberries and strawberries (5–25 mg/100 g fresh weight), sumac (significant levels in berry extract), oak bark, and witch hazel. • Bioactive properties: potent antioxidant with ORAC value significantly higher than ascorbic acid on a molar basis; acts as a free radical scavenger, metal chelator (especially Fe²⁺ and Cu²⁺), and modulator of NF-κB and Nrf2 signaling pathways. • Bioavailability: Oral bioavailability is relatively low (~estimated 10–30% absorption in the upper GI tract); rapidly absorbed in the stomach and small intestine primarily via passive diffusion and monocarboxylic acid transporters. Undergoes extensive phase II metabolism (glucuronidation, sulfation, and methylation) in the liver and intestinal wall, producing 4-O-methylgallic acid, gallic acid-3-O-sulfate, and gallic acid-4-O-glucuronide as major circulating metabolites. Plasma half-life is short (~1–2 hours). Unabsorbed gallic acid reaches the colon where gut microbiota convert it to pyrogallol and catechol derivatives. • Derivatives and related compounds: serves as the monomeric building block of hydrolyzable tannins (gallotannins and ellagitannins); ester forms include epigallocatechin gallate (EGCG) in green tea and propyl gallate (food additive E310). • No significant vitamin, mineral, fiber, or protein content as an isolated compound. • Typical supplemental/research doses: 100–1,000 mg/day orally in human studies; topical formulations commonly at 1–3% concentration. • Solubility: moderately soluble in water (~11.5 g/L at 20°C), freely soluble in ethanol and ethyl acetate, which affects formulation and bioavailability in different delivery systems.
Gallic acid exerts its effects through multiple pathways including inhibition of cyclooxygenase-2 (COX-2) and lipoxygenase enzymes, reducing inflammatory mediator production. It scavenges reactive oxygen species through its phenolic hydroxyl groups and activates antioxidant enzymes like catalase and superoxide dismutase. The compound also modulates glucose metabolism by enhancing insulin sensitivity and inhibiting α-glucosidase activity.
A randomized controlled trial (n=30) demonstrated that 2% topical gallic acid cream reduced melasma severity by 32% over 12 weeks. Another RCT in type 2 diabetics (n=60) showed oral supplementation decreased fasting glucose by 12.5 mg/dL and HbA1c by 0.6%. Blood pressure studies indicate modest reductions of 3.5 mmHg systolic pressure. Evidence quality ranges from moderate to limited due to small sample sizes and short study durations.
Gallic acid is generally well-tolerated with few reported adverse effects at therapeutic doses. High doses may cause gastrointestinal upset including nausea and stomach irritation. It may interact with anticoagulant medications due to potential blood-thinning effects. Pregnant and breastfeeding women should avoid supplementation due to insufficient safety data.
