IngredientsThe term tannates refers to the salts and complexes formed when tannic acid (or tannins more broadly) reacts with another molecule — typically a metal ion, a protein, or an organic base such as a pharmaceutical active ingredient. In natural-product and dietary-supplement contexts the terms tannins, tannic acid, and tannates are closely related and are often used interchangeably; the distinction is primarily chemical. A tannate is the anion (or complex) produced when a tannin acts as the acid partner in a salt-forming reaction, donating its phenolic protons to a basic counterpart.
Naturally occurring tannic acid comprises a mixture of compounds considered to be secondary metabolites, with a molecular weight of 500–5000 Da, for which a rigorous chemical definition is difficult. More broadly, tannins are a family of versatile, natural phenolic biomolecules whose main role is to protect plants against insects and fungi; two main categories can be distinguished — hydrolysable tannins (HTs) and proanthocyanidins (PAs), also known as condensed flavonoid tannins, which are resistant to hydrolytic degradation.
Tannins may be classified chemically into two main groups, hydrolyzable and condensed. Hydrolyzable tannins yield various water-soluble products upon decomposition in water, such as gallic acid and protocatechuic acid and sugars. Gallotannin, or common tannic acid, is the best known of the hydrolyzable tannins.
Hydrolyzable tannins are molecules with a polyol — generally D-glucose — as a central core, with the hydroxyl groups of the carbohydrate partially or totally esterified with phenolic groups; they derive their name from their propensity to be hydrolyzed by mild acids or mild bases to yield carbohydrates and phenolic acids. Condensed tannins (or proanthocyanidins) are polyhydroxyflavan-3-ol oligomers and polymers in which the flavanol subunits are linked through C–C bonds.
In addition to the commonly used classification as hydrolyzable tannins and condensed tannins, tannins can also be categorized into two other types: polyphenols of constant chemical structure (Type A) and polyphenols of variable composition (Type B). Hydrolyzable tannins have polyphenolic cores with molecular weights ranging from 500 to 3000 daltons.
The specific compound most often referred to as tannic acid — and the parent molecule from which most pharmaceutical tannate salts are derived — is a gallotannin. Tannic acid (TA), the simplest hydrolysable tannin, is a U.S. Food and Drug Administration (FDA)-approved food additive; it is composed of a core glucose molecule connected to 10 galloyls by aliphatic ester bonds.
Tannins are secondary metabolic components synthesized from plants. They are ubiquitous throughout the plant kingdom and have been isolated from a wide range of botanical materials. Commercial powder tannins are sourced from at least seven distinct botanical origins: oak, chestnut, gall, quebracho, tea, grape skin, and grape seed.
Specific botanical sources include:
Among the most medicinally relevant tannin-rich plant genera are Acacia, Agrimonia, Camellia, Geranium, Hamamelis, Krameria, Lythrum, Phyllanthus, Potentilla, Quercus, Rhus, Rubus, Sanguisorba, and Terminalia.
Tannates and tannins exist in commerce and research in numerous forms:
Tannins have been used throughout history for their pharmacological properties as part of plants and herbs in traditional medicine. They have been used throughout history for their ethnopharmacological properties in traditional medicine.
Tannins are polyphenolic compounds historically utilized in textile and adhesive industries, but also in traditional human and animal medicines or foodstuffs. They have been used for the process of tanning to transform hides into leather, from which their name derives.
With the upgrading of chemical methods, tannins — alongside saponosides, etheric oils, vitamins, and hormones — were eventually isolated and identified as active substances from medicinal plants, a development that took place primarily in the nineteenth and twentieth centuries.
The use of tannins for treating gastrointestinal diseases can be dated back to the early twentieth century. However, the empirical use of tannin-rich plant preparations for medicinal purposes predates their chemical identification by centuries or millennia. Tannin-rich species have been traditionally described to treat gastrointestinal disorders or diseases (diarrhoea, congestion, anthelmintic), respiratory affections (pharyngitis, cold, expectorant and for sore throat), many skin issues such as eczema, ulcers, leukoderma, and wounds, variable inflammatory processes (toothache, conjunctivitis, menstrual pain, haemorrhoids, smallpox, biliousness) and diabetes.
European traditional medicinal plants such as agrimony, marigold, witch hazel, rose, chamomile, oak, and many others are intended by the European Medicines Agency (EMA) for oral infections and inflammations. The plants mentioned contain mainly polyphenols (flavonoids or tannins) as active compounds with antimicrobial, antioxidant, anti-inflammatory, and wound-healing effects.
In traditional Chinese medicine, plants with high tannin content such as Galla Chinensis (Chinese gall) have been used historically as astringents and intestinal regulators. In the Far East Asiatic cultures, macroalgae such as Sargassum and Ecklonia — sources of phlorotannins — have been used for nutritional purposes and as folk medicine since ancient times.
Tannins contain aromatic rings bearing hydroxyl groups, which give them high chemical activity, causing them to form complexes with other macromolecules, such as carbohydrates or bacterial cell membranes; their main characteristics, however, are complexation and precipitation of proteins.
Key compound classes within the tannate/tannin family include:
Accurate structure-activity correlations on a molecular basis can be determined mainly for hydrolysable tannins such as the ellagitannins and their oxidized congeners, some gallotannins, epigallocatechin gallate, and caffetannins; among the activities determined on a molecular basis are chemical, biological and pharmacological actions such as superoxide anion scavenging, apoptosis, antitumor, anti-EBV, anti-MRSA and anti-plasmin inhibitory activities, in addition to their fundamental activities of binding to proteins, large molecular compounds and metallic ions, and antioxidant activities.
Tannins form complexes with macromolecules including carbohydrates and bacterial cell membranes, with complexation and precipitation of proteins being their main characteristics. Tannins have the ability to bind reversibly to some amino acids and dietary and endogenous proteins. This protein-binding capacity underpins several of their pharmacological effects, from astringency and mucosal protection to enzyme inhibition.
The mechanisms of antioxidation action of tannins include free radical scavenging activity, chelation of transition metals, inhibition of prooxidative enzymes, and inhibition of lipid peroxidation. The main mechanisms by which tannins induce antioxidant functions include the reduction of oxidative stress, the ability to scavenge free radicals, and the modulation of specific enzymes, such as superoxide dismutase.
Both hydrolyzable and condensed tannins have demonstrated the ability to inhibit the growth of several bacterial strains which are potentially pathogenic, such as Escherichia coli, without having any effects on the physiological growth of other gut beneficial bacteria. Their antimicrobial action proceeds via protein precipitation at bacterial cell surfaces, disruption of cell membrane integrity, and metal-ion chelation that deprives bacteria of essential cofactors.
Both hydrolysable tannin from Chinese natural gall and condensed tannin from Acacia mearnsii inhibit salivary and pancreatic α-amylases; the human salivary α-amylase was more strongly inhibited by the hydrolysable form, with IC₅₀ values of 47.0 μM versus 285.4 μM for the condensed form, while pancreatic α-amylase IC₅₀ values were 141.1 μM and 248.1 μM respectively. The kinetics presented complex patterns in which more than one molecule can bind simultaneously to either the free enzyme or the substrate-complexed enzyme (parabolic mixed inhibition); both tannins were able to inhibit intestinal starch absorption.
Tannins directly scavenge reactive oxygen species (ROS) via their polyphenolic structure, mitigate oxidative damage, upregulate antioxidant enzyme expression, suppress pro-inflammatory cytokine secretion, and preserve intestinal barrier integrity. This modulation effectively reduces levels of pro-inflammatory mediators such as TNF-α and IL-1β at the transcriptional and translational levels, while concurrently elevating the expression of the anti-inflammatory cytokine IL-10 — although these findings are derived from cellular models and cannot be directly extrapolated to the clinical setting.
The actions of hydrolyzable tannins on lipid metabolism are several, among which is the inhibition of lipid accumulation; tannins seem to induce a cardioprotective effect, and through various mechanisms, such as the relaxation of vascular smooth muscle, HTs were proven to be efficient against arterial hypertension.
Tannins also interact with the gut microbiota, modulating its composition and activity to promote the growth of beneficial bacteria such as Lactobacillus and Bifidobacterium while inhibiting pathogenic microbes; additionally, tannins improve gut barrier integrity and reduce inflammation, contributing to overall gastrointestinal health.
Although bioavailability and pharmacokinetic data for tannins are still sparse, gut absorption of these compounds seems to be inversely correlated with the degree of polymerization; further studies are mandatory to better clarify how these molecules and their metabolites are able to cross the intestinal barrier in order to exert their biological properties.
Research on the bioavailability and metabolism of tannins remains limited; these properties are closely related to their chemical and biological degradation, polymerization, and solubility. Highly polymerized proanthocyanidins, in contrast to catechins, exhibit poor absorption through the gut barrier and minimal metabolism by the intestinal microflora. Compounds detected in blood or urine often differ significantly from those originally ingested. No specific intestinal receptors for tannin transport have been identified, suggesting that tannins and their precursors may rely on passive diffusion for absorption.
Tannins are an interesting class of polyphenols characterized, in almost all cases, by a different degree of polymerization, which inevitably and markedly influences their bioavailability, as well as biochemical and pharmacological activities.
This is the therapeutic area with the strongest direct clinical evidence for tannate preparations.
Tannin albuminate / ethacridine lactate combination (TA/ET): The efficacy and safety of tannin albuminate and ethacridine lactate monohydrate for the treatment of acute diarrhea and the prevention of traveler's diarrhea are proven in randomized controlled trials (RCTs); several non-interventional studies substantiate the real-world effectiveness and tolerability of the fixed combination; both active ingredients combine antidiarrheal, antimicrobial, mucosal protection, and spasmolytic properties.
The antidiarrheal efficacy of TA/ET has been investigated in RCTs and non-interventional studies including a total of more than 3,000 patients; four RCTs investigated the efficacy of TA/ET in the treatment of acute diarrhea; in a reference-controlled, single-blind, multicenter study by Vorberg et al. (1978), 51 adult outpatients with gastroenteritis, enterocolitis, or summer diarrhea were treated with TA/ET (500 mg/50 mg; 2 tablets four times daily) or tannin albuminate (500 mg; 2 tablets four times daily) for 5 days. The fixed combination reduced acute diarrhea duration by improving stool frequency, consistency, and weight and reduced the risk of traveler's diarrhea; two pilot studies indicate efficacy in chronic diarrhea.
Tannic acid medical food (Cesinex®): The broad-spectrum antidiarrheal effect of Cesinex® can be attributed to a combination of factors: its ability to improve epithelial barrier properties, to inhibit intestinal fluid secretion, and its high antioxidant property. A clinical study showed that the tannic acid-based medical food Cesinex® is effective for broad-spectrum diarrhea and displays a good safety profile.
Evidence quality: Multiple RCTs and non-interventional studies exist for the tannin albuminate / ethacridine lactate combination. Evidence for tannic acid medical food is based on a single clinical study. Overall, the antidiarrheal evidence base for pharmaceutical tannate preparations is among the most clinically substantiated of all tannin applications.
Tannins have demonstrated notable therapeutic potential against ulcerative colitis (UC) due to their inherent antioxidant and anti-inflammatory properties; variations in structural complexity and polymerization degree among botanical sources critically influence their therapeutic efficacy against UC.
Findings from a systematic literature review indicate that tannins directly scavenge ROS via their polyphenolic structure, mitigate oxidative damage, upregulate antioxidant enzyme expression, suppress pro-inflammatory cytokine secretion, and preserve intestinal barrier integrity; despite their significant therapeutic promise, challenges such as low bioavailability and structural complexity remain.
Evidence quality: Predominantly mechanistic and pre-clinical (cellular and animal model) evidence. Translational human trials are lacking. Evidence is preliminary.
Tannins — including oligomeric proanthocyanidins, gallotannins, ellagitannins, catechins, and epigallocatechin gallate — are reviewed as active compounds against oral infectious diseases. Both hydrolyzable and condensed tannins inhibit growth of potentially pathogenic bacterial strains without affecting physiological gut bacteria; tannins bind reversibly to amino acids and dietary and endogenous proteins; a positive effect on Campylobacter jejuni was demonstrated in vitro.
Evidence quality: Evidence is primarily in vitro and pre-clinical. Human clinical evidence for tannins specifically as antimicrobial or oral health agents remains limited.
Both hydrolysable and condensed tannins were able to inhibit intestinal starch absorption; inhibition by the hydrolysable tannin was concentration-dependent, with 53% inhibition at a dose of 58.8 μmol/kg and 88% inhibition at 294 μmol/kg in animal models.
A bibliographic review of antidiabetic tannin effects analyzed data from more than 41 medicinal plants containing tannins and 19 isolated tannins and tannin-rich crude extracts which were found to possess glucose-lowering effects according to pharmacological studies. A clinical trial suggested that baobab tree extract, rich in tannic acid, is beneficial for postprandial glycemic control owing to its antioxidant properties.
Evidence quality: The mechanistic basis (α-amylase inhibition, glucose transport modulation) is reasonably well established in vitro and in animal models. Human clinical evidence is sparse and limited to single-study reports; no large-scale RCTs have confirmed clinically meaningful antidiabetic effects of isolated tannin preparations.
Tannins exhibit high antioxidant properties and have been shown to prevent oxidative-stress-related diseases such as cardiovascular disease, cancer, and osteoporosis. Condensed tannins, particularly proanthocyanidins, consistently display potent antioxidant activity through radical scavenging, metal chelation and activation of endogenous defenses, thereby underpinning their anti-inflammatory, anti-ischemic, neuroprotective, and metabolic actions.
Some studies suggest that tannins can help reduce the risk of cardiovascular diseases, including atherosclerosis and hypertension. Through various mechanisms, such as the relaxation of vascular smooth muscle, HTs were demonstrated to be efficient against arterial hypertension.
Evidence quality: Evidence is primarily from in vitro experiments, animal studies, and epidemiological observations. Large-scale, controlled human trials specifically testing isolated tannin preparations for cardiovascular outcomes are absent from the literature.
Both types of tannins and related polyphenols account for a large part of plant polyphenols, and among the activities determined on a molecular basis are chemical, biological, and pharmacological actions such as superoxide anion scavenging, apoptosis induction, and antitumor activity. Tannic acid has attracted much attention due to its extensive physiological effects, including antitumor actions, in addition to its capability of interacting with various proteins.
Different polyphenols deriving from chestnuts were able to synergistically induce the inhibition of cancerous cells through multiple pathways.
Evidence quality: Entirely pre-clinical (in vitro cell-line and animal model) at this time. No human clinical trials have established tannins as effective anticancer agents. This area remains at the exploratory stage.
Researchers have highlighted tannins' involvement in cardiovascular, neuroprotective, and general metabolic disease prevention. Hydrolysable tannins exert strong antioxidative effects that support antimicrobial activity, enzyme modulation, and protection against neuroinflammation.
A systematic review analyzed pre-clinical research on the treatment of diabetic neuropathic pain using plant phytochemicals containing only tannins; a total of 10 original articles involving in-vivo and in-vitro experiments addressing the promising benefits of tannins on diabetic neuropathic pain were examined between 2008 and 2021; the information implies that these phytochemicals may have relevant pharmacological effects on neuropathic pain symptoms through their antihyperalgesic, anti-inflammatory, and antioxidant properties, however, because of the limited sample size and limitations of the studies conducted, definitive conclusions could not be made.
Evidence quality: Pre-clinical only. No controlled human clinical trials have been conducted to evaluate tannin preparations specifically for neuroprotective outcomes in humans.
The hemostasis system is often affected by complications associated with cardiovascular diseases, which results in thromboembolic events; compounds of plant origin and plant extracts are considered a promising source of substances that could modulate the functioning of the hemostasis system; tannins, which are plant-origin compounds with potential effects in hemostasis, deserve a special mention; the hemostasis-modifying ability of three groups of tannins — ellagitannins, gallotannins, and procyanidins — has been described.
Evidence quality: Evidence remains largely mechanistic and pre-clinical. Human hemostatic effects of tannate preparations have not been demonstrated in controlled trials.
Dosage data are heterogeneous across the literature, reflecting the diversity of tannin types, sources, and therapeutic targets. The following are dosages reported in specific cited sources:
No universally standardized human oral dosing range has been established for tannins as dietary supplements; dosages studied vary substantially depending on the tannin class, botanical source, and intended indication.
Tannins hinder the absorption of essential minerals, vitamins, and proteins, reducing the overall nutritional value of foods. It is accepted that tannins reduce iron availability before absorption through the formation of insoluble antinutritional-mineral complexes. The negative impact of tannins lies in their anti-nutrient effect due to their ability to chelate important minerals such as Fe(II), Cu(II), and Zn(II).
Critically, the degree of iron inhibition observed in single-meal studies may not reflect long-term effects. Previous studies suggest that long-term tannin consumption may not inhibit iron bioavailability as much as single-meal studies predict; long-term antinutritional factor consumption in animals and humans resulted in improved nonheme iron bioavailability compared with single-meal studies; the negative effects of antinutritional factor intake over time were not sustained, proposed to be attributable to adaptation over time.
Studies examining the effect of hydrolysable tannin (tannic acid containing ten gallic acid residues) on iron absorption showed that gallic acid inhibited iron absorption to the same extent as tannic acid per mol galloyl groups, whereas no inhibition was observed when catechin was added to the test meal.
Tannins are often cited for antinutritional effects including chelation of non-heme iron, but studies exploring non-heme iron bioavailability inhibition with long-term consumption have reported mixed results; salivary proline-rich proteins (PRPs) may mediate tannin-antinutritional effects on non-heme iron bioavailability.
Despite the beneficial uses of tannins, they are classified among anti-nutrients reducing the bioavailability of several key nutrients such as heavy metals (e.g., Fe(II) and Cu(II)), vitamins, and proteins, including digestive enzymes (e.g., trypsin, chymotrypsin).
Hydrolyzable tannins are potentially toxic to ruminants; pyrogallol, a hepatotoxin and nephrotoxin, is a product of HT degradation by ruminal microbes; proanthocyanidins are considered to be non-toxic because they are not absorbed. These concerns are documented primarily in veterinary contexts involving ruminant animals, not in human dietary supplement use; the clinical relevance to humans ingesting normal dietary or supplemental amounts remains to be determined.
Tannins are characterized by a different degree of polymerization, which markedly influences their bioavailability as well as biochemical and pharmacological activities; researchers have started to unravel their potential, highlighting anti-inflammatory, antimicrobial, antioxidant and anticancer activities, as well as their involvement in cardiovascular, neuroprotective, and metabolic disease prevention; the mechanisms underlying their activity are often complex, but the main targets include key enzyme modulation, activation of metabolic pathways, and changes in metabolic fluxes — all without losing sight of their toxicity.
Due to their strong protein and metal-binding properties, tannins have the potential to interact with a range of pharmaceutical drugs by reducing their absorption and bioavailability. Due to their structural complexity and capacity to bind proteins and metal ions, tannins exhibit a broad range of biological activities including antioxidant, antimicrobial, anti-inflammatory, and anticancer effects — the same binding properties that confer bioactivity can reduce oral drug bioavailability when co-administered. Research has documented the potential for tannins in Galla Chinensis to affect the pharmacokinetics of rifampicin. The tannate salt complex of an active is a significantly larger molecule, which affords absorption of the active over prolonged intervals of time — a principle exploited in pharmaceutical tannate formulations to achieve sustained release but which also means that tannins can alter the absorption profile of co-administered agents.
Despite significant therapeutic promise, challenges such as low bioavailability and structural complexity remain as key limitations of tannin-based therapeutics and supplements.
Tannins exert several pharmacological effects including antioxidant and free radical scavenging activity as well as antimicrobial, anti-cancer, anti-nutritional and cardio-protective properties; they also seem to exert beneficial effects on metabolic disorders and prevent the onset of several oxidative stress-related diseases.
Across the breadth of studied applications, the antidiarrheal effect of pharmaceutical tannate preparations (particularly tannin albuminate with or without ethacridine lactate) has the strongest human clinical evidence base, supported by multiple RCTs and a substantial non-interventional study population. In all other areas — cardiovascular, anticancer, antidiabetic, neuroprotective, anti-inflammatory — evidence is derived primarily from in vitro and animal models, with only isolated human studies. Many published results are mostly based on in vitro evidence, and there is less focus on bioavailability, detailed mechanisms of action using animal models, and possible toxicities. The field of tannin/tannate research is active and growing, but translation to validated clinical applications beyond gastrointestinal use remains at an early stage.
Health conditions that Tannates may help support.
Body systems that Tannates may help support.
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