Tannins — What They Are, What They Do in the Body, and Why Kakadu Plum Has 11 Named Varieties Including One Unique to This Fruit

Tannins are one of the most studied groups of plant compounds in nutrition science — and one of the least understood by most people who consume them daily. Every cup of tea, glass of red wine, square of dark chocolate and handful of walnuts contains them. They are responsible for the dry, puckering sensation on the tongue. They are the reason unripe fruit is unpleasant and why pomegranate is marketed as an antioxidant powerhouse.

Kakadu plum contains 11 named tannin compounds, identified in a 2022 study of wild-harvested Northern Territory fruit — more named compounds than any other fruit source in the published scientific literature, including pomegranate. One of those tannins was identified so recently that it was named in a 2024 paper and appears to be unique to this fruit.

Kakadu Plum Capsules — whole fruit and seed, 11 named tannins, 64 cents each →

What Tannins Are

Tannins are a family of polyphenol compounds found in plants. They are large molecules with multiple hydroxyl groups, which gives them two key properties: they bind to proteins and minerals, and they donate electrons to free radicals.

Plants produce them as a defence mechanism — against insects, fungi and animals. The astringency you feel from strong tea, unripe fruit or grape skins is tannin doing its job: binding to proteins in your saliva and causing that dry, puckering sensation.

The word comes from their oldest industrial application: tanning leather. Tannins bind to animal hides and convert them to stable, durable leather. The same binding capacity that works on leather proteins works on free radicals in biological systems — which is why tannins are among the most potent plant antioxidants measured.

There are two main families:

• Condensed tannins (proanthocyanidins) — found in grape seeds, bark, berries. These are chains of flavonoid units.
• Hydrolysable tannins (ellagitannins and gallotannins) — found in pomegranate, oak, and Kakadu plum. These break down in the body into smaller active compounds including ellagic acid and gallic acid.

Kakadu plum contains hydrolysable tannins — the same family as pomegranate, which has built an entire supplement industry on a single ellagitannin called punicalagin. Kakadu plum contains punicalagin too — along with ten other named compounds.

What Tannins Do in the Body

In the gut, ellagitannins do two things:

First, they act as antioxidants directly. Their multiple hydroxyl groups donate electrons to free radicals, neutralising them before they can damage cells, proteins and DNA. This is the same mechanism as vitamin C and vitamin E, operating on different parts of the cell.

Second, gut bacteria metabolise them into urolithins. When ellagitannins reach the large intestine, bacteria break them into smaller compounds — ellagic acid first, then further into urolithin A, B and C. Urolithins are currently being studied for their role in mitochondrial function and cellular recycling (mitophagy). Urolithin A is the active compound in one of the most expensive longevity supplements currently on the market — sold at significant cost for what the body makes naturally when it has the right precursor.

The precursor — ellagic acid and ellagitannins — is exactly what Kakadu plum provides in high concentrations.

A 2024 study from the University of Queensland found that gut bacteria break Kakadu plum’s tannins into metabolites with higher antioxidant activity than the original compounds. The antioxidant effect of tannins in the body may be larger after digestion than the FRAP score on the raw fruit suggests. [4]

Foods Highest in Tannins

Tannin content varies enormously between foods. The highest-tannin whole foods that most people consume include:

Pomegranate has built its entire supplement reputation on punicalagin — one compound. Kakadu plum contains punicalagin along with ten additional named tannins, including one that appears to be unique to this species.

All 11 Named Tannins in Kakadu Plum

A 2022 study published in Frontiers in Nutrition (Phan ADT et al., PMC9372433) identified and named the following tannin compounds in wild-harvested Terminalia ferdinandiana fruit: [1]

1. Corilagin — 1.6 to 1.8g per 100g dried fruit. The single most plentiful compound in the whole fruit. An ellagitannin also found in pomegranate, grape and black myrobalan. A 48-hour fermentation study confirmed it remains active through fermentation. [1][2]
2. Ellagic acid — 0.65 to 0.73g per 100g as the free form; 2.8 to 3.4g per 100g when all bound forms are included. The natural precursor to urolithins A and B — compounds currently sold in longevity supplements. [1]
3. Punicalagin — the dominant tannin in pomegranate, and the compound behind pomegranate’s supplement marketing. Also present in Kakadu plum. [1]
4. Castalagin — an ellagitannin found in oak, chestnut and sweet chestnut. Also present in pomegranate. [1]
5. Geraniin — a hydrolysable tannin found in geranium and a small number of tropical fruits. Identified in Kakadu plum at measurable levels. [1]
6. Elaeocarpusin — an ellagitannin originally identified in the Elaeocarpus genus. Its presence in Kakadu plum was confirmed in the 2022 study. [1]
7. Chebulagic acid — found in terminalia species generally (the fruit of Terminalia chebula is called myrobalan). Kakadu plum is itself a Terminalia species. [1]
8. Chebulinic acid — another compound from the terminalia family, present in Kakadu plum. [1]
9. Chebulic acid — the breakdown product of chebulagic acid and chebulinic acid. [1]
10. Helioscopin B — an ellagitannin identified in the 2022 study. Less studied than corilagin but part of the same hydrolysable tannin family. [1]
11. Terminalagin — named after the tree itself (Terminalia ferdinandiana) in a 2024 paper. This compound appears to be unique to Kakadu plum — it has not been identified in any other food source. [5]

Gallic acid — the building block from which ellagic acid and most of the other tannins are formed — is one of the two main polyphenols in the fruit alongside ellagic acid. It is present alongside all of the above compounds. [1]

The Pomegranate Connection — Punicalagin

Pomegranate’s supplement reputation rests almost entirely on one compound: punicalagin. The market for pomegranate extract, pomegranate juice concentrate and POM Wonderful’s patent claims all flow from studies on this single ellagitannin and its breakdown into urolithin A.

Punicalagin is present in Kakadu plum. [1]

But Kakadu plum also contains corilagin — which at 1.6 to 1.8g per 100g is more abundant than punicalagin in pomegranate by weight. It contains ellagic acid across all its forms at up to 3.4g per 100g. It contains castalagin, the same ellagitannin also found in pomegranate. And it contains terminalagin — a compound that does not exist in pomegranate or any other identified food source.

Pomegranate’s marketing is built on one compound. Kakadu plum contains eleven.

The Urolithin Story — Ellagic Acid

Urolithin A is currently sold as a longevity supplement targeting mitochondrial health and cellular recycling. It is produced by gut bacteria from ellagic acid and ellagitannins — the compounds found in high concentrations in pomegranate and Kakadu plum.

The supplement market exists because only about 40% of people produce urolithins in significant quantities from diet alone. Whether you produce them depends on your individual gut microbiome. Urolithin A supplements bypass the gut microbiome and deliver the compound directly.

The relevant point for Kakadu plum: ellagic acid in all its forms is present at up to 3.4g per 100g of dried fruit. [1] For people whose gut microbiome does convert ellagitannins, Kakadu plum provides the precursor at high concentration. The 2024 University of Queensland research confirms that gut bacteria do metabolise Kakadu plum tannins — and that the resulting metabolites show higher antioxidant activity than the original compounds. [4]

Corilagin — The Most Plentiful Single Compound in the Fruit

Corilagin is worth highlighting separately because of its quantity. At 1.6 to 1.8 grams per 100 grams of dried fruit, it is the most abundant single compound in the whole Kakadu plum — including vitamin C. [1]

It belongs to the ellagitannin family, the same class as punicalagin and ellagic acid. It is also found in pomegranate, grape, and several Terminalia species. A fermentation study confirmed that corilagin remains active through 48 hours of fermentation — relevant because some processing and preservation methods degrade polyphenols before they reach the consumer. [2]

Corilagin has been studied in multiple scientific contexts. Its concentration in Kakadu plum is one of the highest recorded for any food source.

Terminalagin — Named After the Tree

Every other tannin in the list above also exists in other plants. Pomegranate contains punicalagin. Oak and chestnut contain castalagin. Geraniin is found in geranium. These are shared compounds across a range of plant species.

Terminalagin is different. It was identified and named in a 2024 scientific paper (PubMed ID 41391874). It is named after Terminalia ferdinandiana — the scientific name of the Kakadu plum tree. [5] It has not been identified in any other food source.

Science is still characterising this fruit. Terminalagin’s discovery in 2024 means that after decades of study on Kakadu plum, researchers are still finding compounds that do not exist anywhere else in the botanical world.

Are Tannins Good or Bad?

Tannins have been called antinutrients because they bind to minerals — particularly iron — reducing their absorption in the gut. This is a real, measurable effect.

But it requires context:

The binding is strongest when tannin-rich food is consumed at the same time as an iron-rich meal. Eating tannin-rich foods between meals, or with meals low in iron, produces a much smaller effect.

More importantly: vitamin C reverses this. Vitamin C enhances iron absorption and counteracts the inhibitory effect of tannins on iron uptake. Foods that contain both high tannins and high vitamin C — like Kakadu plum — do not carry the same risk as tannin-only sources.

Our Kakadu plum powder delivers 60mg of vitamin C per 500mg capsule — alongside the tannins. The mineral-binding concern that applies to black tea (which has tannins but minimal vitamin C) does not apply in the same way to whole Kakadu plum fruit.

People with established iron deficiency should still avoid taking any concentrated tannin supplement at the same time as iron-rich foods. For most people eating a varied diet, the antioxidant benefit of tannin-rich whole foods outweighs the mineral-binding concern.

Why Our Capsules Contain the Whole Fruit — Seed and All

Most Kakadu plum products use only the dried fruit flesh. Ours uses whole fruit powder — fruit and seed kernel together, ground to the same fine consistency throughout. The seed kernel is milled to the same standard as the fruit, producing a smooth powder with no grit. That level of processing takes more work.

We do it because the numbers are worth it. The seed kernel carries the highest concentrations of every mineral the body uses in its antioxidant and cellular protection processes:

• Zinc: 6.0mg per 100g in the seed — 10 times more than the fruit flesh (0.57mg)
• Copper: 2.5mg per 100g in the seed — 8 times more than the fruit flesh (0.30mg)
• Manganese: 9.1mg per 100g in the seed — 2.6 times more than the fruit flesh (3.5mg)
• Iron: 6.1mg per 100g in the seed — 50% more than the fruit flesh (4.0mg)

The seed also carries 32% protein, 35% fat (four-fifths unsaturated), 21% fibre, 539mg calcium, 421mg magnesium and 669mg potassium per 100g. No other Kakadu plum supplement we are aware of includes the seed.

Kakadu Plum Capsules — whole fruit and seed, 64 cents each, 140 capsules →

For the full antioxidant picture — vitamin C, vitamin E, tannins, flavonoids and carotenoids together — see our antioxidant rich foods page.

Frequently Asked Questions

What are tannins?

Tannins are a family of polyphenol compounds found in plants. They are large molecules with multiple hydroxyl groups, which gives them the ability to bind to proteins, minerals and other molecules — and to donate electrons to free radicals, making them potent antioxidants. Plants produce them as a defence mechanism. In food and drink, tannins are responsible for the dry, puckering sensation — the astringency you feel from strong tea, red wine, unripe fruit or dark chocolate. The word comes from their historical use in tanning leather, where tannins bind to animal hides and convert them to stable leather.

What do tannins do in the body?

Tannins act as antioxidants in the body, donating electrons to free radicals and preventing them from damaging cells, proteins and DNA. The ellagitannins in Kakadu plum — including corilagin and punicalagin — are also metabolised by gut bacteria into smaller compounds called urolithins. Urolithins (particularly urolithin A) have been studied for their role in supporting mitochondrial function and cellular recycling (mitophagy). Research from the University of Queensland (2024) found that gut bacteria break Kakadu plum tannins into metabolites that show higher antioxidant activity than the original compounds — meaning the full antioxidant effect of tannins may be larger after digestion than laboratory tests on the raw fruit suggest.

Are tannins good or bad for you?

Tannins have been called antinutrients because they can bind to iron and other minerals, reducing their absorption in the gut. This is a real effect, but context matters. The binding occurs mainly when tannin-rich food and an iron-rich meal are consumed at the same time. Vitamin C — which Kakadu plum contains in very high quantities — counteracts this effect directly: it enhances iron absorption and effectively reverses the inhibitory effect of tannins on iron uptake. People with established iron deficiency should avoid consuming large amounts of tannins with iron-rich foods. For most people consuming tannins as part of a whole food, the antioxidant benefit outweighs the mineral-binding concern.

What foods are highest in tannins?

Foods highest in tannins include pomegranate (marketed heavily on its punicalagin content), grape skins and red wine, black tea and green tea, dark chocolate and cocoa, walnuts and chestnuts, berries, and unripe fruit. Kakadu plum stands out because it contains not one or two named tannins but 11 named compounds — including punicalagin (the same tannin pomegranate is marketed on), corilagin (1.6 to 1.8 grams per 100g dried fruit, making it the most plentiful single compound in the whole fruit), ellagic acid (up to 3.4g per 100g across all its forms), and terminalagin — a tannin so recently discovered it was named in a 2024 scientific paper and appears to be unique to Kakadu plum.

What is terminalagin?

Terminalagin is a tannin so recently identified that it was named in a 2024 scientific paper (PubMed 41391874). It is named after Terminalia ferdinandiana — the scientific name of the Kakadu plum tree — and appears to be unique to this species. It belongs to the ellagitannin family, the same group as corilagin, punicalagin and ellagic acid. Its identification represents the ongoing scientific discovery around Kakadu plum: researchers are still characterising compounds in this fruit that do not exist in any other food source.

What is corilagin?

Corilagin is an ellagitannin — one of the class of tannins found in Kakadu plum, pomegranate, and a small number of other plant sources. In Kakadu plum, it is the single most plentiful compound in the whole fruit, measured at 1.6 to 1.8 grams per 100 grams of dried fruit. A fermentation study confirmed corilagin remains active through a 48-hour fermentation process. It belongs to the same compound family as punicalagin (the tannin pomegranate is most associated with) and ellagic acid. Corilagin has been studied in multiple contexts; its high concentration in Kakadu plum makes it one of the fruit’s most scientifically interesting compounds.

Do tannins survive digestion?

Tannins are partially absorbed and partially metabolised by gut bacteria. A 2022 study modelling Kakadu plum through a simulated digestion process found that ellagic acid survived at 33% to 48% of its original concentration. University of Queensland research from 2024 found that gut microbes break the large tannins (ellagitannins) into smaller compounds called urolithins — and those urolithins showed higher antioxidant activity in lab tests than the original tannin compounds. This suggests the antioxidant benefit of tannins may be greater after digestion than laboratory tests on the raw fruit alone indicate. Whether a person produces urolithins depends on their individual gut microbiome.

References

1. Phan ADT et al. Hydrolysable tannins of wild-harvested Terminalia ferdinandiana fruit at different maturity stages. Frontiers in Nutrition, 2022. PMC9372433.
2. Akter S et al. In vitro Bioaccessibility and Intestinal Absorption of Bioactive Compounds in Terminalia ferdinandiana. Frontiers in Nutrition, 2022. PMC8828953.
3. Konczak I, Zabaras D, Dunstan M et al. Health Benefits of Australian Native Foods. RIRDC (Australian Government) Pub. No. 09/133, Sept 2009.
4. Kaur P et al. Gut microbiota-mediated transformation of polyphenols from Terminalia ferdinandiana. University of Queensland, 2024.
5. Terminalagin, a New Ellagitannin from Kakadu Plum. PubMed 41391874.

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