Thearubigins are the reddish-brown pigments of black tea, a loose family of large polyphenols (plant compounds) that form when tea leaf is oxidized. Enzymes in the cut and rolled leaf first turn green tea catechins into orange-red theaflavins. Further oxidation then produces thearubigins.
E. A. H. Roberts named them in 1958 and explained that the word means, literally, the rusty-brown substances of tea. Together with theaflavins, they carry almost all the color of a black tea liquor.
Nobody has drawn one, because there is no single one to draw. In 2010 Kuhnert wrote that, 50 years after the name was introduced, the chemical nature of thearubigins remained largely unresolved, if not mysterious. His group analyzed thearubigins from 15 commercial black teas. They found more than 5,000 individual components, none above 2,000 daltons (a unit of molecular size).
A 2022 mouse study found that gut bacteria break thearubigins down into theaflavins, theasinensins and catechins. That fits the idea that they are built from those units.
One thing most people do not know is how little agreement there is on how much of black tea they make up. Roberts put them at more than 10% of the dry matter of tea. A 2026 survey that measured 32 Assam black teas found 6.0% to 14.5% of the dry leaf. Kuhnert estimated about 60% of the solids in a typical infusion.
The figures use different bases and different assays. The USDA lists 81.3 mg per 100 g for brewed black tea and 1.08 mg for brewed green tea.
Health benefits of thearubigins
No trial in people has tested thearubigins on their own, so none of the findings below reaches strong evidence. The human work is two small studies of black tea that followed a breakdown product in urine. There are also four observational studies of intake, and only one looked at thearubigins alone; it found little link to lung cancer.
Most of the rest is animal and cell work, mainly with thearubigin fractions isolated from black tea. It points to protection in mouse models of colitis, liver injury and skin and oral cancer. But one mouse study found no protection against lung tumors. Here is what 19 studies found, strongest evidence first, including the results that found nothing.
Black tea roughly doubled a gut-bacteria product in urine, versus caffeine
17 healthy men on a low-polyphenol diet took part in this randomized crossover trial. Each treatment lasted 2 days: 6 g a day of black tea solids, 6 g of green tea solids or 360 mg of caffeine. The authors link urinary hippuric acid to gut bacteria acting on tea polyphenols. It was 3.75 mmol/24 h on black tea, about as much as 4.22 on green tea, against 1.89 on caffeine. Little is known about how bacteria break down thearubigins, and the trial measured a breakdown product, not thearubigins or any health outcome.
6 to 10 mugs of black tea daily raised urinary hippuric acid
9 habitual tea drinkers ate a low-polyphenol, low-caffeine diet for 6 days. From day 4 they added strong black tea, and a 24-hour urine was collected each day. Hippuric acid rose from 153-512 to 742-1,374 mg a day. The authors calculated that the other tea compounds could not supply enough benzoic acid, so thearubigins may be a source. Those compounds were gallic acid, flavanols, flavonol glycosides and theaflavins. That is an inference, not a measurement, and it was not a randomized trial.
Moderate theaflavin plus thearubigin intake went with less COPD, not asthma
This cohort study followed 119,466 adults in the UK Biobank (median age 60), with flavonoid intake estimated from 24-hour diet assessments. Moderate intake went with up to 18% lower risk of COPD, a chronic lung disease, than low intake. That held for these pigments and for total flavonoids, flavonols and flavanones. Unlike the other groups, higher theaflavin plus thearubigin intake did not go with better FEV1, a lung function measure. The two pigments were analyzed together, and observational data cannot show cause.
Thearubigin intake showed little link to lung cancer
This population-based case-control study compared 558 lung cancer cases and 837 controls, with intake estimated from a food questionnaire and food composition data. Among tobacco smokers, higher intake of epicatechin, catechin, quercetin and kaempferol went with less lung cancer. Regardless of smoking status, there was little association with thearubigins, hesperetin, naringenin or myricetin. Observational data cannot show cause.
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In older adults, no reported blood pressure link for theaflavins plus thearubigins
This cross-sectional analysis covered 381 non-smoking healthy adults (mean age 66) in an Australian longevity study. Intake of several flavonoid groups, with theaflavins and thearubigins taken together, was estimated from food questionnaires and USDA databases. Central blood pressure and arterial stiffness were tied to anthocyanin and flavanone intake, and the abstract reports no link for the tea pigments. Each standard deviation more anthocyanin went with 1.56 mmHg lower central diastolic pressure. More flavanone went with about 1% lower augmentation index, but cross-sectional data cannot show cause.
In US women, these pigments were linked to gallstones, direction unclear
This cross-sectional study of 4,087 US adults (NHANES 2017-2018) used 29 flavonoids in six subclasses. About 11% reported gallstones, and total flavonoid intake showed a U-shaped link. Theaflavins and thearubigins were among the flavonoids linked to gallstones in women, but the abstract does not give the direction for each. Combined-exposure models showed a positive link overall and in women but not in men; gallstones were self-reported, and the data cannot show cause.
In mice, gut bacteria broke thearubigins into smaller tea compounds
This lab study used germ-free and specific pathogen-free mice, with mass-spectrometry analysis. Gut bacteria broke thearubigins down into theaflavins and theasinensins, and four breakdown products reached the urine. Chemical breakdown of thearubigins with menthofuran also gave theaflavins, theasinensins and catechins, so the authors conclude that thearubigins are complex polymers of these units. They describe thearubigins as poorly absorbed and say their structures and actions in the body are still largely unknown.
Thearubigin eased chemically induced colitis in mice
Mice got 40 mg/kg a day of thearubigin by stomach tube for 10 days before TNBS, a chemical that causes colitis (gut inflammation). Thearubigin reduced diarrhea, damage to the colon, neutrophil infiltration and lipid peroxidation, and lowered nitric oxide, superoxide and serine protease activity. NF-kappa B activation in the colon fell, and a dose of 100 mg/kg had comparable effects. It was a mouse model, and the authors only suggest it may prove useful in inflammatory bowel disease.
After an acetaminophen overdose, thearubigins protected mouse liver and kidney
Groups of 8 mice got a toxic dose of acetaminophen (300 mg/kg). 1.5 hours later they got N-acetylcysteine, black tea extract or thearubigins at 50, 60 or 70 mg/kg, injected into the abdomen. Thearubigins reversed the rise in the liver enzyme ALT and the damage marker MDA, restored glutathione, and eased liver and kidney damage. The effect grew with dose and was largest at 60 to 70 mg/kg, most at 70 mg/kg, where it was similar to N-acetylcysteine. The doses were injected, not eaten.
Thearubigin reduced lung inflammation in newborn rats with lung injury
In this rat model, acute lung injury was caused by LPS, a bacterial toxin. Thearubigin lowered the lung wet-to-dry weight ratio, protein in lung fluid, MPO activity and cytokine levels. It lowered the oxidative markers H2O2, MDA and hydroxyl ions, and switched on the Nrf2 antioxidant response. The abstract gives no dose, and the authors say more work is needed on how it acts.
At a 10% dose, thearubigins left hamsters with no oral tumors
Hamsters in a model of carcinogen-induced oral cancer received polymeric black tea polyphenols, the thearubigin fraction, at 1.5%, 5% or 10% before and during exposure. Tumor number and volume fell with dose, and no tumors, visible or microscopic, were seen at 10%. The fraction also lowered oxidative DNA damage, COX-2, cell proliferation markers and EGFR-Akt-mTOR signaling. It prevented tumors in animals and says nothing yet about people.
Thearubigin fractions curbed skin tumor promotion in mice, some more than others
Mice were pretreated with five polymeric black tea polyphenol fractions, PBP-1 to PBP-5. Then they got DMBA to start skin tumors and TPA to promote them for 40 weeks. Pretreatment changed the latency, number and incidence of skin papillomas. Most fractions lowered TPA-induced cell proliferation and signaling through JNK, ERK, p38, Akt, AP-1, NF-kappa B and COX-2. PBP-2 was the most potent, PBP-4 and PBP-5 only marginal, and PBP-1 and PBP-3 in between.
Thearubigins did not prevent lung tumors in mice
A/J mice received the thearubigin fraction at 1.5%, 5% or 10%, before and during exposure to benzo[a]pyrene. This carcinogen is found in tobacco smoke. Tumor incidence and multiplicity did not fall, and early molecular markers did not change. The same group had earlier seen protection against a mix of two carcinogens, so the effect seems to depend on the carcinogen. The senior author also led the oral cancer study above.
In cells, thearubigins mimicked insulin on a glucose-making gene
This screen of dietary compounds used a mammalian cell model. Three theaflavin gallates and thearubigins copied the effect of insulin and IGF-1 on the transcription factor FOXO1a. They did the same on PEPCK, a liver gene for making glucose. The authors add that green tea EGCG seemed to work after conversion into such larger structures. Little is known about how available black tea polyphenols are in the body.
Thearubigins weakened colon and lung cancer cells in a dish
This cell study used HCT 116 colon and HT 460 lung cancer cells. Thearubigins, theaflavins and their combinations cut cell viability, more at higher doses, and caused cell cycle arrest at G2/M and apoptosis (cell death). Theaflavins had the largest effect on viability, and the combination gave the most apoptosis. The authors say clinical work is needed first.
A thearubigin diet lowered blood fats and glucose in rats
40 rats (10 per group) with arginine-induced kidney malfunction ate a control diet or one with theaflavins, thearubigins or both for 56 days. The abstract gives the amount as 1 g, with no unit. The theaflavin and thearubigin diets lowered the lipid profile, glucose, kidney function tests and TBARS, and raised insulin and HDL. Theaflavins did better on blood fats, and the mixed diet on glucose, urea, creatinine and insulin. Test-tube antioxidant tests in the same paper also favored theaflavins.
A thearubigin fraction raised muscle mitochondrial proteins in trained mice
This protein study of mouse skeletal muscle compared mice with and without endurance training. It used a butanol-soluble thearubigin fraction that the authors call mitochondrial activation factor. With training, it raised proteins of the energy-making electron transport chain and citric acid cycle, partly through AMPK alpha subunits. Without exercise it brought only a slight rise in actin, and the authors say how it affects AMPK is not yet clear.
In a test tube, thearubigin curbed fat damage like theaflavins did
This test-tube study used rat liver homogenate. The concentrations that cut lipid peroxidation by half were 4.88, 4.09 and 4.95 (in units of 0.0001% w/v) for theaflavin, theaflavin monogallate-A and thearubigin. All three beat glutathione, vitamin C, vitamin E and BHT, but were weaker than epicatechin gallate, epigallocatechin and EGCG. Black tea infusion was about as potent as green tea.
A thearubigin fraction lowered drug-processing gut enzymes in rats
Rats ate theaflavins or theafulvins, a fraction of thearubigins, for 4 weeks. Neither changed liver cytochrome P450 activity or liver conjugating enzymes. In the intestine, both suppressed CYP1A1 activity and lowered CYP3A protein, and theafulvins also inhibited glucuronosyl transferase. Whether this matters for drug interactions in people is not known.
Foods high in thearubigins
Thearubigins are a black tea compound, formed when the leaf is oxidized. The USDA ranking below lists only green tea, at 1.08 mg per 100 g or 2.65 mg in a cup. It leaves out black tea, the real source.
In the same USDA release, brewed black tea has 81.3 mg per 100 g, about 75 times more. So the table after the ranking adds the black tea rows and published measurements.
A 245 g cup of brewed black tea holds about 199 mg, by our arithmetic from the USDA value. The USDA range of 48.28 to 139.5 mg per 100 g covers about 118 to 342 mg a cup. Decaffeinated, bottled and instant black teas have less, and only teas carry a thearubigin value in the USDA data.
In dry leaf, 32 Assam black teas held 6.0% to 14.5%. Other studies found lower figures with other assays, so compare numbers within one study.
In population surveys, black tea dominates thearubigin intake. Estimated intake reached 532.5 mg a day in UK men in EPIC, and thearubigins were 58% of flavonoid intake in 1,183 Australians. Black tea was the source of more than half of thearubigin intake in Korea.
Per serving. No daily amount is set, so bars compare each food with the top food.
Per 100 g. No daily amount is set, so bars compare each food with the top food.
Per 100 kcal: the same calories of each food, for a fair comparison. Bars compare each food with the top food.
Food labels have no Daily Value or Reference Intake for thearubigins, so the % compares each food with the top food.
| Food | Amount per 100 g (unless noted) | Source |
|---|---|---|
| Brewed black tea (USDA, 32 studies) | 81.3 mg (range 48.28 to 139.5) | 1 |
| Brewed decaffeinated black tea (USDA, 4 studies) | 49.03 mg (range 46.05 to 51.52) | 1 |
| Ready-to-drink black tea, plain and flavored (USDA, 17 studies) | 25.49 mg (range 7.8 to 56.78) | 1 |
| Prepared instant tea, unsweetened (USDA, 3 studies) | 23.65 mg (range 8.35 to 39.02) | 1 |
| Brewed green tea (USDA, 4 studies) | 1.08 mg (range 0 to 4.3) | 1 |
| Black tea leaf, dry (32 teas from Assam) | 5.96 to 14.54 g (published as 59.62 to 145.37 mg/g) | 2 |
| Black tea leaf, dry (51 teas from different regions) | 2.59 to 9.23 g (published as 25.92 to 92.29 mg/g, average 46.08) | 3 |
| Black tea, dry (5 Bangladeshi brands) | 2.32 to 6.65 g (published as TR % by spectrophotometry) | 4 |
| Made tea, dry matter (Roberts, 1958) | More than 10 g | 5 |
Sources
- USDA Database for the Flavonoid Content of Selected Foods, Release 3.3. Bhagwat S, Haytowitz DB. US Department of Agriculture, Agricultural Research Service. 2018.
- Sarmah PP, Deka H, Parasar P, et al. Biochemical quality profile of black tea from Upper Assam and North Bank region of Assam, India. Foods. 2026.
- Wang W, Le T, Wang W, et al. Effects of key components on the antioxidant activity of black tea. Foods. 2023.
- Munim Khan MR, Islam MA, Uddin R, et al. Biochemical investigation of Bangladeshi black tea and their correlation to organoleptic quality evaluation. Heliyon. 2023.
- Roberts EAH. The estimation of the theaflavins and thearubigins in made teas. Tea Quarterly. 1958;29(2):99-100. Reprinted from Two and a Bud, 1958.
- Zamora-Ros R, Knaze V, Romieu I, et al. Impact of thearubigins on the estimation of total dietary flavonoids in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Eur J Clin Nutr. 2013.
- Murphy KJ, Walker KM, Dyer KA, Bryan J. Estimation of daily intake of flavonoids and major food sources in middle-aged Australian men and women. Nutr Res. 2019.
- Kim YJ, Park MY, Chang N, Kwon O. Intake and major sources of dietary flavonoid in Korean adults: Korean National Health and Nutrition Examination Survey 2010-2012. Asia Pac J Clin Nutr. 2015.
How thearubigins work
Most of what is known about how thearubigins act comes from test tubes, cells and animals. Much of it was done with thearubigin fractions isolated from black tea, not with one compound. Four ideas come up. They are a mixture of thousands of large molecules, and gut bacteria break them into smaller pieces.
They hold back oxidation in test tubes, and in animals they dampen inflammation and cell-growth signals. Here is each one, and what has been seen in people.
They are a mixture, not one molecule
Because no single structure exists, researchers work with thearubigin fractions, which differ from lab to lab. Kuhnert’s group found that the fractions from 15 commercial teas were remarkably similar in their spectroscopic fingerprint. Their data fit structures of not more than 2,000 daltons that clump together in water. These keep the handedness of the flavanols and theaflavins they come from.
Only a small share of what the mass spectrometer sees can be named. Formulas matched 15 compounds from fresh leaf that survived processing, and 21 dimeric products such as theasinensins, theaflavins and theacitrins. In a test tube, thearubigin also sticks to the surface of a protein, bovine serum albumin, by electrostatic attraction and hydrogen bonding.
Drawn to scale. The counts come from different instruments and are not the same kind of number, so read them as a sense of size: thousands of signals, a few dozen identified structures. The peaks are from six teas (FT-ICR-MS) and the component estimate is an average over the 15 teas (MALDI-TOF-MS).
Gut bacteria take them apart
Thearubigins are large and poorly absorbed, so the gut is where much of the action is thought to take place. In germ-free and ordinary mice, gut bacteria turned thearubigins into theaflavins and theasinensins, and four breakdown products were found in urine. In people, much less is known. A 2013 review by Clifford and colleagues found surprisingly little research on how black tea thearubigins and theaflavins are absorbed and metabolized.
Not drawn to scale. The results come from germ-free and ordinary mice. The study did not measure how much is absorbed.
Human studies hint at the same breakdown. In 9 habitual tea drinkers, 6 to 10 mugs of black tea a day raised urinary hippuric acid. It went from 153-512 to 742-1,374 mg a day, and a calculation suggested thearubigins may be an important source.
In a randomized crossover trial in 17 men, 6 g of black tea solids a day gave 3.75 mmol of hippuric acid per 24 hours. On caffeine alone it was 1.89. Neither study measured thearubigins in blood or urine.
They hold back oxidation in test tubes
In rat liver homogenate, thearubigin halved lipid peroxidation at about the same concentration as theaflavin. That was lower than needed for several common antioxidants. In newborn rats with lung injury, thearubigin lowered oxidative markers and turned on Nrf2, a master switch for the cell’s own protective enzymes. In mice given acetaminophen, it restored glutathione and lowered the damage marker MDA.
In cultured cells, thearubigins copied insulin’s action on FOXO1a, a transcription factor. The authors note that little is known about how available black tea polyphenols are in the body.
Drawn to scale. A shorter bar means a lower concentration was enough, so a stronger effect, by weight. This was a test-tube experiment in rat liver homogenate.
A result that disagrees: a 2023 analysis of 51 black teas looked at which components best tracked the tea’s antioxidant activity. It found that catechins did, not thearubigins.
They dampen inflammation and growth signals in animals
In mice with chemical colitis, thearubigin lowered neutrophil infiltration and lipid peroxidation, and suppressed NF-kappa B activation in the colon. In mouse skin, thearubigin fractions lowered activation of kinases, AP-1, NF-kappa B and COX-2, and altered tumor latency and number. In hamsters, a 10% dose of the fraction left no oral tumors, with less EGFR-Akt-mTOR signaling. In mouse muscle, a fraction raised mitochondrial proteins when combined with training, partly through AMPK.
Results are not all one way. The same lab that saw protection in hamsters found no protection against lung tumors caused by benzo[a]pyrene in mice. One rat study also found that thearubigin-type fractions lowered intestinal CYP1A1 and CYP3A. That matters for the section on medicines below.
What has been seen in people
Very little. No trial has given people thearubigins on their own. The two black tea studies in the cards above show that tea rich in thearubigins changes a bacterial product in urine. They do not show that it changes health.
In observational studies, thearubigin intake showed little link to lung cancer. Moderate intake of theaflavins plus thearubigins went with lower COPD risk, but not with better lung function. The abstract of a blood pressure study reports no link for the pair, and a gallstone study found one in women without giving the direction.
All of these estimate intake from food tables. In 2013 the EPIC authors wrote that there is no appropriate food composition data on thearubigins. They said further work on identifying and quantifying them is needed. The animal findings above have therefore not been tested in people.
Sources
- Kuhnert N. Unraveling the structure of the black tea thearubigins. Arch Biochem Biophys. 2010.
- Kuhnert N, Drynan JW, Obuchowicz J, Clifford MN, Witt M. Mass spectrometric characterization of black tea thearubigins leading to an oxidative cascade hypothesis for thearubigin formation. Rapid Commun Mass Spectrom. 2010.
- Haslam E. Thoughts on thearubigins. Phytochemistry. 2003.
- Chitpan M, Wang X, Ho CT, Huang Q. Monitoring the binding processes of black tea thearubigin to the bovine serum albumin surface using quartz crystal microbalance with dissipation monitoring. J Agric Food Chem. 2007.
- Wang W, Ohland C, Jobin C, Sang S. Gut microbiota as a novel tool to dissect the complex structures of black tea polymers. J Agric Food Chem. 2022.
- Clifford MN, van der Hooft JJ, Crozier A. Human studies on the absorption, distribution, metabolism, and excretion of tea polyphenols. Am J Clin Nutr. 2013.
- Clifford MN, Copeland EL, Bloxsidge JP, Mitchell LA. Hippuric acid as a major excretion product associated with black tea consumption. Xenobiotica. 2000.
- Mulder TP, Rietveld AG, van Amelsvoort JM. Consumption of both black tea and green tea results in an increase in the excretion of hippuric acid into urine. Am J Clin Nutr. 2005.
- Yoshino K, Hara Y, Sano M, Tomita I. Antioxidative effects of black tea theaflavins and thearubigin on lipid peroxidation of rat liver homogenates induced by tert-butyl hydroperoxide. Biol Pharm Bull. 1994.
- Wang X, He P, Yi S, Wang C. Thearubigin regulates the production of Nrf2 and alleviates LPS-induced acute lung injury in neonatal rats. 3 Biotech. 2019.
- Murad HA, Habib H, Kamel Y, et al. Thearubigins protect against acetaminophen-induced hepatic and renal injury in mice: biochemical, histopathological, immunohistochemical, and flow cytometry study. Drug Chem Toxicol. 2016.
- Cameron AR, Anton S, Melville L, et al. Black tea polyphenols mimic insulin/insulin-like growth factor-1 signalling to the longevity factor FOXO1a. Aging Cell. 2008.
- Wang W, Le T, Wang W, et al. Effects of key components on the antioxidant activity of black tea. Foods. 2023.
- Maity S, Ukil A, Karmakar S, et al. Thearubigin, the major polyphenol of black tea, ameliorates mucosal injury in trinitrobenzene sulfonic acid-induced colitis. Eur J Pharmacol. 2003.
- Nimbalkar VK, Gangar J, Shai S, et al. Prevention of carcinogen-induced oral cancers by polymeric black tea polyphenols via modulation of EGFR-Akt-mTOR pathway. Sci Rep. 2022.
- Patel R, Krishnan R, Ramchandani A, Maru G. Polymeric black tea polyphenols inhibit mouse skin chemical carcinogenesis by decreasing cell proliferation. Cell Prolif. 2008.
- Shaikh ZM, Bhatia N, Aradhye P, et al. Thearubigins/polymeric black tea polyphenols (PBPs) do not prevent benzo[a]pyrene (B[a]P) induced lung tumors in A/J mice. Am J Transl Res. 2023.
- Zhu K, Ozawa T, Yu C, et al. Black tea thearubigins extract facilitated endurance training-induced promotion of aerobic capacity in mice skeletal muscle. Food Res Int. 2025.
- Catterall F, McArdle NJ, Mitchell L, et al. Hepatic and intestinal cytochrome P450 and conjugase activities in rats treated with black tea theafulvins and theaflavins. Food Chem Toxicol. 2003.
- Bondonno NP, Parmenter BH, Thompson AS, et al. Flavonoid intakes, chronic obstructive pulmonary disease, adult asthma, and lung function: a cohort study in the UK Biobank. Am J Clin Nutr. 2024.
- Cui Y, Morgenstern H, Greenland S, et al. Dietary flavonoid intake and lung cancer: a population-based case-control study. Cancer. 2008.
- Parmenter BH, Croft KD, Cribb L, et al. Higher habitual dietary flavonoid intake associates with lower central blood pressure and arterial stiffness in healthy older adults. Br J Nutr. 2022.
- Lin J, Lin X, Chen Y, Yang L, Xiu X. U-shaped association between dietary flavonoid and gallstone prevalence with sex-specific effects: insights from a cross-sectional study. J Int Med Res. 2026.
- Zamora-Ros R, Knaze V, Romieu I, et al. Impact of thearubigins on the estimation of total dietary flavonoids in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Eur J Clin Nutr. 2013.
Are thearubigins safe? Supplements, dose and interactions
Thearubigins at the amounts in black tea are not a known safety concern. Black tea is a common drink, and estimated thearubigin intake reached 532.5 mg a day in UK men. We found no acceptable daily intake, upper level, FDA GRAS notice or EFSA assessment for thearubigins themselves. No thearubigin supplement has been tested in people, and the research products are fractions isolated from tea.
- Trial doses and side effects. We found no trial of purified thearubigins in people, so no dose has been tested. The human studies gave black tea: 6 g of tea solids a day for 2 days, or 6 to 10 mugs a day. Neither abstract reports side effects, but neither looked for them. In the mug study, some volunteers processed more benzoic acid than its acceptable daily intake, which the authors do not consider a hazard.
- Animal doses. In the colitis study, mice got 40 to 100 mg/kg by stomach tube. In the acetaminophen study, they got 50 to 70 mg/kg by injection. Animal doses are not a guide to human doses.
- Medicines. In rats, thearubigin-type fractions lowered intestinal CYP1A1 and CYP3A protein, and theafulvins inhibited an intestinal conjugating enzyme. We found no human interaction studies. Ask a pharmacist if you take medicines and drink a lot of black tea.
- Iron, caffeine and other groups. Black tea cut iron absorption from a bread meal by 79% to 94% in adults. That was tea, not thearubigins alone, but people with low iron may want to ask about timing. Black tea also carries caffeine: 15.51 to 39.24 mg per gram of leaf in 32 Assam teas. We found no thearubigin studies in pregnancy, breastfeeding or children.
How to get more thearubigins
- Best food. Brewed black tea: 81.3 mg per 100 g in the USDA data, about 199 mg in a 245 g cup by our arithmetic. Green tea has 1.08 mg per 100 g.
- Brew it hot. In a Turkish study of 2,688 cups, brewing water temperature had the broadest effect on thearubigins. The thearubigin value, published as a percentage, rose from 12.8 at 75 °C to 16.8 at 90 °C and 19.6 at 95 °C. Another study found that the amounts of tea and water, infusion time, stirring and bag type also change what reaches the cup.
- Food versus supplement. No thearubigin supplement has been tested in people. Other black tea products carry less, by our arithmetic from USDA values. Decaffeinated brewed tea has about 60% of the thearubigins of regular brewed tea, bottled black tea about 31% and prepared instant tea about 29%.
Sources
- Clifford MN, Copeland EL, Bloxsidge JP, Mitchell LA. Hippuric acid as a major excretion product associated with black tea consumption. Xenobiotica. 2000.
- Mulder TP, Rietveld AG, van Amelsvoort JM. Consumption of both black tea and green tea results in an increase in the excretion of hippuric acid into urine. Am J Clin Nutr. 2005.
- Maity S, Ukil A, Karmakar S, et al. Thearubigin, the major polyphenol of black tea, ameliorates mucosal injury in trinitrobenzene sulfonic acid-induced colitis. Eur J Pharmacol. 2003.
- Murad HA, Habib H, Kamel Y, et al. Thearubigins protect against acetaminophen-induced hepatic and renal injury in mice: biochemical, histopathological, immunohistochemical, and flow cytometry study. Drug Chem Toxicol. 2016.
- Catterall F, McArdle NJ, Mitchell L, et al. Hepatic and intestinal cytochrome P450 and conjugase activities in rats treated with black tea theafulvins and theaflavins. Food Chem Toxicol. 2003.
- Hurrell RF, Reddy M, Cook JD. Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. Br J Nutr. 1999.
- Sarmah PP, Deka H, Parasar P, et al. Biochemical quality profile of black tea from Upper Assam and North Bank region of Assam, India. Foods. 2026.
- Zamora-Ros R, Knaze V, Romieu I, et al. Impact of thearubigins on the estimation of total dietary flavonoids in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Eur J Clin Nutr. 2013.
- Cho JM, Abanoz YY, Boyraz A, et al. Effects of brewing conditions on the sensory and chemical properties of Turkish black tea and their interrelationships. Sci Rep. 2026.
- Astill C, Birch MR, Dacombe C, Humphrey PG, Martin PT. Factors affecting the caffeine and polyphenol contents of black and green tea infusions. J Agric Food Chem. 2001.
- USDA Database for the Flavonoid Content of Selected Foods, Release 3.3. Bhagwat S, Haytowitz DB. US Department of Agriculture, Agricultural Research Service. 2018.
History of thearubigins
In 1958 E. A. H. Roberts reported on the color of a black tea liquor that comes from oxidation products. Nearly all of it belongs to two classes of substances that chemists had not recognized before. He suggested calling them thearubigins and theaflavins.
The thearubigins, he wrote, account for more than 10 percent of the total dry matter of tea. There seemed to be several closely related substances in the class. He found that strength tracked the sum of both groups. Good color went with a high total and a relatively high ratio of theaflavin to thearubigin.
The structure turned out to be much harder than the color. Haslam reviewed the chemistry of tea leaf fermentation in 2003 to propose structures for thearubigins. In 2010 Kuhnert wrote that their chemical nature remained largely unresolved after 50 years.
His group used data methods borrowed from petroleum analysis on mass spectra of thearubigins from 15 teas. They proposed an oxidative cascade hypothesis for how thearubigins form. Making black tea is often called fermentation, although the work is done by enzymes in the leaf, not by microbes.
Health research has lagged behind. In 2013 Clifford and colleagues noted surprisingly little research on how black tea thearubigins are absorbed and metabolized. The same year, the EPIC authors said that no appropriate food composition data existed. In 2022, germ-free mice showed that gut bacteria break thearubigins into theaflavins, theasinensins and catechins.
Sources
- Roberts EAH. The estimation of the theaflavins and thearubigins in made teas. Tea Quarterly. 1958;29(2):99-100. Reprinted from Two and a Bud, 1958.
- Haslam E. Thoughts on thearubigins. Phytochemistry. 2003.
- Kuhnert N. Unraveling the structure of the black tea thearubigins. Arch Biochem Biophys. 2010.
- Kuhnert N, Drynan JW, Obuchowicz J, Clifford MN, Witt M. Mass spectrometric characterization of black tea thearubigins leading to an oxidative cascade hypothesis for thearubigin formation. Rapid Commun Mass Spectrom. 2010.
- Sarmah PP, Deka H, Parasar P, et al. Biochemical quality profile of black tea from Upper Assam and North Bank region of Assam, India. Foods. 2026.
- Clifford MN, van der Hooft JJ, Crozier A. Human studies on the absorption, distribution, metabolism, and excretion of tea polyphenols. Am J Clin Nutr. 2013.
- Zamora-Ros R, Knaze V, Romieu I, et al. Impact of thearubigins on the estimation of total dietary flavonoids in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Eur J Clin Nutr. 2013.
- Wang W, Ohland C, Jobin C, Sang S. Gut microbiota as a novel tool to dissect the complex structures of black tea polymers. J Agric Food Chem. 2022.
- Thearubigin. Wikipedia.
Frequently asked questions about thearubigins
What are thearubigins?
Thearubigins are the reddish-brown pigments of black tea, a mixture of large polyphenols formed when green tea catechins are oxidized during processing. Kuhnert’s group found more than 5,000 individual components in thearubigins from 15 black teas. The structure of the group is still largely unresolved. Roberts named them in 1958 and put them at more than 10% of the dry matter of tea.
What do thearubigins do for the body?
No one knows yet in people. No trial has tested thearubigins on their own. Mouse and rat studies found protection in models of colitis, liver and kidney injury and skin and oral cancer. But one mouse study found no protection against lung tumors. The human studies are a few observational ones, mostly grouping thearubigins with theaflavins, and none shows cause.
Which foods are high in thearubigins?
Black tea is the source. The USDA lists 81.3 mg per 100 g for brewed black tea, against 1.08 mg for brewed green tea. Decaffeinated black tea has 49.03 mg, bottled black tea 25.49 mg and prepared instant tea 23.65 mg per 100 g. Only teas carry a thearubigin value in the USDA data.
How much thearubigin is in a cup of black tea?
About 199 mg in a 245 g cup, by our arithmetic from the USDA value of 81.3 mg per 100 g. The USDA range gives about 118 to 342 mg. Brewing matters: in a Turkish study, the thearubigin value rose from 12.8 at 75 °C to 19.6 at 95 °C.
Are thearubigins absorbed by the body?
Mostly not as whole molecules. In mice, gut bacteria broke them into theaflavins, theasinensins and catechins, and four breakdown products reached the urine. In people, 6 to 10 mugs of black tea a day raised urinary hippuric acid from 153-512 to 742-1,374 mg a day. A 2013 review found surprisingly little research on how they are absorbed.
Are thearubigins safe, and do they have side effects?
At the amounts in black tea they are not a known concern. But we found no official safety limit for them and no human supplement trials. Black tea cut iron absorption from a bread meal by 79% to 94%, and it also contains caffeine. In rats, thearubigin-type fractions lowered intestinal drug-processing enzymes, and no human interaction studies exist, so ask a pharmacist if you take medicines.
What is the difference between thearubigins and theaflavins?
Theaflavins are the smaller orange-red pigments that form first. Thearubigins are the larger, more varied red-brown ones that follow from further oxidation. In 32 Assam teas, theaflavins were 4.88 to 15.54 mg/g of dry leaf and thearubigins 59.62 to 145.37 mg/g. In mice, gut bacteria turned thearubigins back into theaflavins. See the page on theaflavins.
Is there thearubigin in green tea?
Only a little. The USDA lists 1.08 mg per 100 g for brewed green tea, with a range of 0 to 4.3 in 4 studies. That is about 75 times less than brewed black tea at 81.3 mg. Thearubigins form during the oxidation step of black tea making.