Gallic acid

Gallic acid at a Glance

Gallic acid is a small trihydroxybenzoic acid and the building block of the gallotannins — the hydrolysable tannins of oak, witch hazel, tea and pomegranate are built from it, esterified to a sugar core.

That makes it one of the most widely encountered phenolic acids in medicinal plants, usually released by hydrolysis of a larger tannin rather than eaten free.

It is a well-characterised dietary antioxidant, with metabolic and gastroprotective activity that remains largely preclinical.

What It's Used For

Gallic acid is a small trihydroxybenzoic acid — a simple phenolic acid that also forms the core unit of the gallotannins (hydrolysable tannins). It is one of the most widely distributed dietary phenolics, abundant in clove, oak galls, black tea, berries and nuts, and it turns up across this database as a member of many herbs’ tannin/phenolic fraction rather than as an isolated drug. Its defining property is antioxidant chemistry — the trihydroxy ring is a potent radical scavenger and metal chelator ^{4Reference 4Kahkeshani N et al. · 2019ReviewPharmacological effects of gallic acid in health and diseases: a mechanistic reviewView study →} — but the practical story is shaped by its pharmacokinetics: gallic acid is absorbed and cleared rapidly (plasma half-life ~1 hour) and is extensively converted to weaker metabolites ^{12Reference 12Shahrzad S et al. · 2001Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humansView study →}, so most of the striking potency seen in a test tube does not translate to achievable human blood levels. Almost all disease-outcome evidence is preclinical; there is a single verified trial of the isolated molecule.

One human isolate trial:gallic acid 200 mg/day for 12 weeks produced modest reductions in waist measures and skinfolds in obese subjects — but mainly in the arm that also exercised, so the isolate’s own contribution can’t be separated ^{1Reference 1Barbosa BK et al. · 2026RCTCombined Effects of Gallic Acid Supplementation and Physical Training on Body Composition and Biochemical Parameters in Obese Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical TrialView study →}.

Strong mechanism, weak translation:a well-substantiated antioxidant and partial-PPARγ/GLUT4 metabolic mechanism ^{2,4Reference 2Gandhi GR et al. · 2014Gallic acid attenuates high-fat diet/streptozotocin-induced insulin resistance via partial agonism of PPARγ and GLUT4 translocation through PI3K/p-Akt signallingView study →Reference 4Kahkeshani N et al. · 2019ReviewPharmacological effects of gallic acid in health and diseases: a mechanistic reviewView study →}, undercut by ~1-hour clearance and low bioavailability ^{12Reference 12Shahrzad S et al. · 2001Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humansView study →}.

The honest headline:gastroprotective, anticancer and antimicrobial reputations rest on whole-extract or in-vitro work, not on isolated gallic acid.

Evidence by IndicationStrength of support · Beta

Support is an experimental score — weighted by study type (human > animal > in vitro) and volume. A beta, not a validated metric. Gallic acid’s isolate evidence is thin and mostly preclinical, so scores stay low by design. Each application links to its write-up.

This is the only application with human isolate data. In high-fat-diet/STZ diabetic rats, gallic acid acted as a partial PPARγ agonist and promoted GLUT4 translocation via PI3K/Akt, improving insulin sensitivity ^{2Reference 2Gandhi GR et al. · 2014Gallic acid attenuates high-fat diet/streptozotocin-induced insulin resistance via partial agonism of PPARγ and GLUT4 translocation through PI3K/p-Akt signallingView study →}, a result echoed with Emblica-derived gallic acid ^{3Reference 3Variya BC et al. · 2019Antidiabetic potential of gallic acid from Emblica officinalis: improved glucose transporters and insulin sensitivity through PPAR-γ and Akt signallingView study →}.

A 2026 double-blind RCT then gave gallic acid 200 mg/day for 12 weeks to obese adults with and without physical training: the supplemented-and-trained group showed modest but significant reductions in waist-to-hip ratio, waist circumference and pectoral/abdominal skinfolds, plus a rise in serum albumin ^{1Reference 1Barbosa BK et al. · 2026RCTCombined Effects of Gallic Acid Supplementation and Physical Training on Body Composition and Biochemical Parameters in Obese Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical TrialView study →}.

A separate in-vitro thread adds a plausible fat-handling angle: gallic acid inhibits pancreatic lipase through hydrogen-bonding and hydrophobic interaction, a rationale for modulating dietary-fat absorption ^{11Reference 11Zhang Y et al. · 2022Characterization, antioxidant activities, and pancreatic-lipase inhibitory effect of extract from the edible insect Polyrhachis vicinaView study →}.

Gap: the human effects were small and concentrated in the exercise-plus-supplement arm, so gallic acid’s own contribution can’t be isolated; no glycemic endpoint reached significance for the isolate, the lipase result is purely in-vitro at unknown gut-relevant concentrations, and no stand-alone diabetes RCT exists ^{1,11Reference 1Barbosa BK et al. · 2026RCTCombined Effects of Gallic Acid Supplementation and Physical Training on Body Composition and Biochemical Parameters in Obese Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical TrialView study →Reference 11Zhang Y et al. · 2022Characterization, antioxidant activities, and pancreatic-lipase inhibitory effect of extract from the edible insect Polyrhachis vicinaView study →}.

Mechanisms

Target / pathway	Effect	Relevant to
Direct radical scavenging + Fe/Cu chelation	neutralizes ROS, blocks Fenton chemistry	antioxidant (all uses)
Nrf2 / antioxidant-enzyme induction	↑ endogenous SOD, catalase, glutathione	antioxidantgastroprotection
PPARγ partial agonism	improved adipocyte insulin sensitivity	metabolic
GLUT4 translocation via PI3K/Akt	↑ muscle glucose uptake	metabolic
Pancreatic lipase inhibition (in vitro)	↓ gut triglyceride hydrolysis	body composition
ROS burst → caspase activation, cycle arrest	pro-apoptotic in tumor cells	anticancer (preclinical)
Microbial membrane disruption	bacteriostatic within extracts	antimicrobial

Pharmacokinetics

Gallic acid’s pharmacokinetics are the decisive caveat. In healthy volunteers given ~50 mg (as supplement or tea), it was absorbed rapidly but eliminated just as fast — mean plasma half-life ≈ 1.1 hours, with Cmax only ~1.8–2.1 µmol/L ^{12Reference 12Shahrzad S et al. · 2001Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humansView study →}. It is heavily biotransformed: the dominant circulating metabolite is 4-O-methylgallic acid (COMT-type methylation), alongside pyrogallol from decarboxylation, then phase-II sulfation and glucuronidation, with additional gut-microbial degradation. Free unconjugated gallic acid is therefore short-lived and low, and its main metabolites are weaker antioxidants than the parent — which is why in-vitro potency reads across poorly to human effect ^{12Reference 12Shahrzad S et al. · 2001Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humansView study →}.

Clinical trials

There is essentially one verified randomized trial of isolated gallic acid (Barbosa 2026, obesity ± exercise) ^{1Reference 1Barbosa BK et al. · 2026RCTCombined Effects of Gallic Acid Supplementation and Physical Training on Body Composition and Biochemical Parameters in Obese Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical TrialView study →}, plus a healthy-volunteer pharmacokinetic study ^{12Reference 12Shahrzad S et al. · 2001Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humansView study →} and a plant-tea biomarker study ^{5Reference 5Colpo AC et al. · 2014Antioxidant effects of Phyllanthus niruri tea on healthy subjectsView study →}. All disease-outcome efficacy (metabolic, gastroprotective, anticancer, antimicrobial) is otherwise rodent, extract-based or in-vitro.

Completed	Planned	Terminated	Preclinical
1isolate RCT (body composition)	—	—	Extensive

Last checked: July 2026.

Toxicity & Safety

Gallic acid is a ubiquitous dietary phenolic (tea, clove, berries, nuts, red wine) and is regarded as low-toxicity at dietary and studied supplemental doses; the 200 mg/day human trial reported no safety signal ^{1,4Reference 1Barbosa BK et al. · 2026RCTCombined Effects of Gallic Acid Supplementation and Physical Training on Body Composition and Biochemical Parameters in Obese Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical TrialView study →Reference 4Kahkeshani N et al. · 2019ReviewPharmacological effects of gallic acid in health and diseases: a mechanistic reviewView study →}. The caveats are largely theoretical and preclinical: like many polyphenols it can turn pro-oxidant at high concentrations (redox cycling that generates hydrogen peroxide), relevant only to supraphysiologic exposure; as a phenolic acid it is a substrate for COMT-type methylation and can compete at CYP and UGT/SULT metabolic routes, so additive or competitive drug-metabolism interactions are plausible but not clinically documented for the isolate; and its mild glucose-lowering action creates a theoretical additive effect with antidiabetic agents. Astringency/tannin cautions properly attach to the tannin-rich whole herbs, not to the purified acid. No verified human interaction or contraindication dataset exists for isolated gallic acid.

Dosage

There is no established therapeutic dose for gallic acid, and the figures here are research doses, not a recommendation. The single human isolate trial used 200 mg/day orally for 12 weeks ^{1Reference 1Barbosa BK et al. · 2026RCTCombined Effects of Gallic Acid Supplementation and Physical Training on Body Composition and Biochemical Parameters in Obese Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical TrialView study →}; the pharmacokinetic study used a single ~50 mg dose ^{12Reference 12Shahrzad S et al. · 2001Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humansView study →}; rodent metabolic studies typically used ~10–25 mg/kg ^{2,3Reference 2Gandhi GR et al. · 2014Gallic acid attenuates high-fat diet/streptozotocin-induced insulin resistance via partial agonism of PPARγ and GLUT4 translocation through PI3K/p-Akt signallingView study →Reference 3Variya BC et al. · 2019Antidiabetic potential of gallic acid from Emblica officinalis: improved glucose transporters and insulin sensitivity through PPAR-γ and Akt signallingView study →}, which does not translate directly to humans. Given rapid clearance (half-life ~1 hour), any biological effect likely depends on repeated intake rather than single doses ^{12Reference 12Shahrzad S et al. · 2001Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humansView study →}.

References

Barbosa BK, et al. (2026). Combined Effects of Gallic Acid Supplementation and Physical Training on Body Composition and Biochemical Parameters in Obese Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical Trial. Nutrients. https://pubmed.ncbi.nlm.nih.gov/41599924/
Gandhi GR, Jothi G, Antony PJ, et al. (2014). Gallic acid attenuates high-fat diet/streptozotocin-induced insulin resistance via partial agonism of PPARγ and GLUT4 translocation through PI3K/p-Akt signalling. European Journal of Pharmacology. https://pubmed.ncbi.nlm.nih.gov/25445038/
Variya BC, Bakrania AK, Patel SS, et al. (2019). Antidiabetic potential of gallic acid from Emblica officinalis: improved glucose transporters and insulin sensitivity through PPAR-γ and Akt signalling. Phytomedicine. https://pubmed.ncbi.nlm.nih.gov/31064680/
Kahkeshani N, Farzaei F, Fotouhi M, et al. (2019). Pharmacological effects of gallic acid in health and diseases: a mechanistic review. Iranian Journal of Basic Medical Sciences. https://pubmed.ncbi.nlm.nih.gov/31156781/
Colpo AC, et al. (2014). Antioxidant effects of Phyllanthus niruri tea on healthy subjects. Asian Pacific Journal of Tropical Medicine. https://pubmed.ncbi.nlm.nih.gov/24461523/
Staszowska-Karkut M, Materska M (2020). Phenolic composition, mineral content, and beneficial bioactivities of leaf extracts from black currant, raspberry, and aronia. Nutrients. https://pubmed.ncbi.nlm.nih.gov/32059465/
Agnihotri VK, et al. (2008). Antioxidant constituents of Nymphaea caerulea flowers. Phytochemistry. https://pubmed.ncbi.nlm.nih.gov/18534639/
Almeida GVB, Arunachalam K, Balogun SO, et al. (2018). Chemical characterization and evaluation of gastric antiulcer properties of the hydroethanolic extract of the stem bark of Virola elongata. Journal of Ethnopharmacology. https://pubmed.ncbi.nlm.nih.gov/30415060/
Basile A, et al. (2005). Antibacterial and antioxidant activities of ethanol extract from Paullinia cupana Mart. Journal of Ethnopharmacology. https://pubmed.ncbi.nlm.nih.gov/16040216/
Prado Martin JG, et al. (2013). Antimicrobial activity of yerba mate (Ilex paraguariensis) against food pathogens. Revista Argentina de Microbiología. https://pubmed.ncbi.nlm.nih.gov/23876271/
Zhang Y, et al. (2022). Characterization, antioxidant activities, and pancreatic-lipase inhibitory effect of extract from the edible insect Polyrhachis vicina. Frontiers in Nutrition. https://pubmed.ncbi.nlm.nih.gov/35464030/
Shahrzad S, Aoyagi K, Winter A, Koyama A, Bitsch I (2001). Pharmacokinetics of gallic acid and its relative bioavailability from tea in healthy humans. The Journal of Nutrition. https://pubmed.ncbi.nlm.nih.gov/11285327/