Gallocatechin (GC)

Gallocatechin, or GC, is a flavan-3-ol. That is the plant compound family that holds catechin and the green tea catechins EGC and EGCG. Compared with catechin, GC carries one extra hydroxyl group on its side ring, three instead of two.

Plants use it for defense. A fungus carried by bark beetles can infect Norway spruce. When it did, the gallocatechin in the bark and wood rose, and by more than catechin did. In the lab, GC held back the fungus’s melanin pigment more than catechin did. Catechin was better at stopping the fungus from growing.

In food, gallocatechin is mostly a tea story. The Japanese biochemist Michiyo Tsujimura first isolated it from green tea in 1934.

It is a minor tea catechin. In USDA data, green tea holds 1.54 mg of GC per 100 g, against 29.2 mg of EGC and 70.2 mg of EGCG. GC and EGC have the same atoms and differ only in how the middle ring is arranged: trans in GC and cis in EGC.

Heat adds a twist. Canned and bottled tea drinks contain GC along with other close cousins of the tea catechins, called epimers. In the lab, autoclaving (pressure-heating) a green tea extract at 120 °C for 20 minutes produced them. So some of the GC in a bottle may come from the factory rather than the leaf.

We found no trial that gave people GC on its own, so what it does for health is mostly unknown.

Health benefits of gallocatechin

• ★Brain-imaging change, but no better test scoresIn 35 healthy adults, one 900 mg dose of a green tea extract rich in GCG (a related molecule, not GC) changed a brain-imaging signal. Cognitive test scores did not differ.
• Population studyLinked to lower death risk in metabolic syndromeIn US adults with metabolic syndrome, higher gallocatechin intake from food went with a lower risk of death (0.71 times the risk). There was no link to heart-related death, and it cannot be separated from other tea compounds.

Foods high in gallocatechin

Green tea is the one food with a clear amount of gallocatechin in USDA data. It holds 1.54 mg per 100 g, or 3.77 mg in a 245 g cup. Everything else in the ranking below holds far less. Blueberries have 0.12 mg per 100 g and plums 0.09, and the ranking shows the rest.

Heating changes tea. Canned and bottled tea drinks contain GC, and in one lab test, autoclaving a tea extract at 120 °C for 20 minutes produced it. A green tea extract heat-processed at 121 °C for 1 minute still held GC among the eight flavanols identified in it.

We found no paper that measured GC in bottled and brewed tea side by side, so we cannot say how much more a bottle holds. GC turns up in other plants too. It was purified from pomegranate peel, and in a test tube a banana fruit homogenate turned EGC into GC.

How gallocatechin works

Almost nothing is known about how gallocatechin works in people. Most tea research is on EGCG, so we use only work that names GC. That work comes from test tubes, cells and animals.

It points to three ideas. GC scavenges radicals, but less than EGC. It slowed cancer cell growth in a dish at doses far above blood levels. And gut bacteria change it. Here is each one, and what has been seen in people.

It scavenges radicals, but less than EGC

Radicals are reactive molecules that can damage fats and proteins, and antioxidant tests measure how well a compound calms them. In three test-tube tests (human LDL oxidation, FRAP and DPPH), GC was less potent than EGC. That is even though the two have the same atoms and differ only in the arrangement of the middle ring.

Purified from pomegranate peel, GC alone also scavenged less than linked pairs of GC units in a water-based test. The authors of the epimer study concluded that the heat conversion in bottled tea would not much change a drink’s overall antioxidant activity or absorption.

It slowed cancer cell growth in a dish, at doses far above blood levels

In a cell study, GC at 50 µM blocked most of the growth of human breast, colon and lung cancer cells. GCG, its gallate relative, blocked 97%, 93% and 67%. Catechin and epicatechin did nothing even at twice that dose.

Blood holds far less. In ten people who drank 500 mL of green tea, single tea metabolites peaked at 29 to 126 nM in blood. Those are metabolites of several tea compounds, not free GC, so the comparison is rough. But the gap is about 400 times.

Gut bacteria change it

A lot of tea flavan-3-ol passes on to the colon. Some people have an ileostomy, an opening that bypasses the colon. When they drank green tea, 70% of the flavan-3-ols was still in the fluid leaving the small intestine. A third of it was unchanged. In a lab dish, three of four gut bacteria broke GC down, and we do not know what the breakdown products do in people.

What has been seen in people

Not much. No trial tested GC on its own. The only human trial used a GCG-rich extract and, for a day, changed a brain-imaging signal without changing test scores. One cohort linked higher dietary GC to lower mortality in metabolic syndrome, but it cannot separate GC from other tea compounds.

Absorption studies report GC and EGC together as “(epi)gallocatechin”. In ten people drinking 500 mL of green tea, urine held (epi)gallocatechin metabolites equal to 11.4% of the amount in the tea. So the lab findings above are ideas to test, not proven effects.

Is gallocatechin safe? Supplements, dose and interactions

Green tea as a drink is judged safe at usual intakes. But as far as we found, no official body has set an acceptable intake or upper level for gallocatechin on its own.

EFSA, the EU’s food safety agency, issued a 2018 opinion on green tea catechins. It said catechins from traditionally prepared green tea infusions are in general considered safe at the intakes reported in the EU. Its concern was EGCG, the main tea catechin. It noted rare cases of liver injury after drinking infusions, most probably an individual (idiosyncratic) reaction. It also noted higher serum transaminases (liver enzymes) at 800 mg of EGCG a day or more from supplements. The opinion gives no figure for GC.

• Doses in trials. We found no trial of GC alone. The one human trial gave a single 900 mg dose of a GCG-rich extract to 35 healthy adults. Its abstract says nothing about side effects, and GCG is a different molecule.
• Liver. The liver signal belongs to EGCG-rich supplements, and whether GC adds to it is unknown. Ask a doctor before taking green tea extract supplements if you have liver problems.
• Drugs and pregnancy. We found no studies of GC with medicines, and none in pregnancy or breastfeeding, so ask your doctor.

How to get more gallocatechin

• Best food. Green tea, at 1.54 mg per 100 g in USDA data. The next food, blueberries, holds 0.12 mg per 100 g.
• Bottled tea. Heat processing forms GC from other tea catechins, so canned and bottled teas contain it. We found no numbers that compare bottled with brewed tea.
• Absorption. In ten people drinking 500 mL of green tea, urine held (epi)gallocatechin metabolites equal to 11.4% of the amount in the tea. The paper does not separate GC from EGC. In rats, bioavailability was low (0.08 to 0.31) for tea catechins and their epimers. We found no data on taking GC with fat or food.

History of gallocatechin

Gallocatechin was found in green tea. The Japanese agricultural chemist Michiyo Tsujimura worked out much of what tea contains. She isolated catechin from green tea in 1929 and earned a doctorate in agriculture in 1932, the first woman in Japan to do so.

In 1934 she reported another tea compound as a new catechin, which she called tea catechin II, or gallo-catechin.

The heat story came later. Hong Kong researchers studying canned and bottled tea showed in 2001 that autoclaving turns EGCG into its epimer GCG. In 2004 they showed that the same treatment of a tea extract yields GC from EGC, along with other epimers.

In 2018, researchers in Germany and South Africa showed that Norway spruce builds more gallocatechin from catechin when a fungus attacks. So the plant side of GC is about defense too.

Frequently asked questions about gallocatechin

What does gallocatechin do for the body?

Nobody knows yet, because no trial has tested it on its own. In the lab it scavenged radicals less strongly than EGC. At 50 µM it blocked most growth of cancer cells, but blood levels after tea are at least 400 times lower. One US cohort of adults with metabolic syndrome linked higher gallocatechin intake to a lower risk of death (hazard ratio 0.71). None of this reaches moderate evidence.

Which foods are high in gallocatechin?

Green tea, by a wide margin. USDA data give 1.54 mg per 100 g, or 3.77 mg in a 245 g cup. Blueberries have 0.12 mg per 100 g and plums 0.09, and the ranking above shows the rest. Canned and bottled tea drinks also contain it, because heat forms it.

What is the difference between gallocatechin and epigallocatechin (EGC)?

They have the same atoms and differ only in the arrangement of the middle ring: trans in GC and cis in EGC. In USDA data, green tea holds 1.54 mg of GC and 29.2 mg of EGC per 100 g, about 19 times more EGC. In the lab, GC was a weaker antioxidant than EGC. See our pages on EGC and EGCG.

Does bottled tea have more gallocatechin than brewed tea?

Possibly, but we found no measurement that compares them. Canned and bottled drinks contain GC because heat during manufacture turns other catechins into epimers. In one lab test, autoclaving a tea extract at 120 °C for 20 minutes did this. That study concluded that the change would not much alter the total antioxidant activity or absorption of tea polyphenols.

What is the difference between gallocatechin and gallocatechin gallate (GCG)?

GCG is a different molecule that carries a galloyl group, and GC does not. The only human trial we found used a GCG-rich extract, so it tells us nothing direct about GC. In the cell test above, GC blocked 87% of lung cell growth and GCG 67%, while GCG did better on breast and colon cells.

How much gallocatechin should you take?

No dose has been tested or set. We found no trial of GC on its own. The nearest human dose, 900 mg of a GCG-rich extract once, is not a GC dose. EFSA gives no figure for GC, and its liver concern is for 800 mg of EGCG a day or more from supplements. Drinking tea is how most people get GC.

Does gallocatechin have side effects?

None are reported for GC on its own, because it has not been tested alone. EFSA found rare liver injury linked to green tea infusions, most probably an individual reaction. It also found raised liver enzymes at 800 mg of EGCG a day or more from supplements. We found no studies of GC with medicines or in pregnancy.

Is gallocatechin a strong antioxidant?

In the test tube it works, but less well than EGC. GC was less potent than EGC in three tests, and GC-containing dimers from pomegranate peel beat the GC monomer in a water-based test. Whether this matters in the body is unknown, and no trial measured it for GC.