What is ginkgo leaf, and how does it differ from the seed?

Ginkgo leaf is the leaf of Ginkgo biloba, a tree so ancient that it is known as a living fossil. Today the leaf is used mostly as an extract, and it is analysed for two main groups of compounds: flavonol glycosides and terpene lactones. In 99 batches of leaves from China, these made up about 0.38–2.08% and 0.03–0.87% of the leaf. The seed, called pae kuai (แปะก๊วย) in Thailand and eaten in sweet soups and Chinese-style dishes, is a different part with a different main compound, ginkgotoxin.

In short:

• What it is: the leaf of Ginkgo biloba, the only living species of the family Ginkgoaceae
• Other names: fossil tree, maidenhair tree, Kew tree, bai guo ye; in Thai, ใบแปะก๊วย for the leaf and แปะก๊วย for the seed
• Main compounds in the leaf: flavonol glycosides and terpene lactones (ginkgolides and bilobalide), plus ginkgolic acids, which extracts keep low
• What changes the amounts: growing region, altitude and soil; studies disagree on whether harvest time matters
• Watch out for: people who are pregnant or breastfeeding, and anyone on regular medication, should ask a doctor or pharmacist; fresh seeds are toxic to eat

What kind of plant is ginkgo?

NCCIH, part of the US National Institutes of Health, describes ginkgo as a deciduous tree so ancient that it is commonly known as a living fossil, and as the last remaining species of a primitive family of plants. A 2008 review by Singh and colleagues in India says the tree has existed on earth for about 200 million years.

Scientific name and family

Its scientific name is Ginkgo biloba. In NCBI Taxonomy, it sits in the genus Ginkgo, family Ginkgoaceae and order Ginkgoales, within the gymnosperms, the seed plants that also include pines.

Other names

How is ginkgo leaf different from the ginkgo seed?

The leaf and the seed come from the same tree, but they are used in different ways and are known for different compounds. NCCIH says that today the leaf, usually as an extract, is the most commonly used form of ginkgo. The seed is the part sold as food.

Sources: NCCIH; van Beek and Montoro 2009; Gong and colleagues 2018; Kong and colleagues 2026.

What compounds are in ginkgo leaves?

A 2009 review by van Beek and Montoro in the Journal of Chromatography A, from Wageningen University in the Netherlands, gathered about 400 papers on the chemical analysis of ginkgo. It lists the important constituents as terpene trilactones (ginkgolides A, B, C, J and bilobalide), flavonol glycosides, biflavones, proanthocyanidins, alkylphenols, simple phenolic acids, 6-hydroxykynurenic acid, 4-O-methylpyridoxine and polyprenols.

The two groups that are measured most

Source: PubChem. Flavonol glycosides are a large family of compounds rather than one substance, so they are not listed in the table.

How are flavonol glycosides measured?

The van Beek and Montoro review explains that no method yet measures all the major flavonol glycosides one by one, because most of them cannot be bought as reference standards. Instead, laboratories break them down with acid into three simpler compounds, quercetin, kaempferol and isorhamnetin, measure those, and then calculate back to an estimate of the total. Quercetin is also found in many everyday foods; see quercetin in everyday food.

What is in the rest of an extract?

The same review notes that terpene trilactones, flavonol glycosides and ginkgolic acids have been the subject of a very large number of papers, while the other constituents, which make up about 70% of standardised ginkgo extracts, have far fewer. Proanthocyanidins alone make up about 7%, and no reliable way of measuring them existed at the time. In the most common standardised extracts, several of the classes found in the leaf are no longer present.

What are ginkgolic acids?

Ginkgolic acids are alkylphenols, a group of compounds found in ginkgo. Van Beek and Montoro write that their toxicity when taken by mouth has never been proven beyond doubt, and that dozens of papers on how to measure them have been published. As a specification for the raw material, most suppliers limit their content in extracts to 5 ppm (5 parts per million, or 5 mg per kg). In 2009 the authors wrote that a method able to detect less than 5 ppm would be added to the European Pharmacopoeia, a European quality standard.

Do the amounts in ginkgo leaves differ by place and season?

Yes, and by a lot. Three studies from China and India show how wide the range is.

The two studies used different methods, so their numbers should not be compared row by row. What they show is that leaves from different places can differ several-fold, or in the Chinese study, by more than twentyfold for terpene lactones.

Altitude

In the Indian study by Kaur and colleagues, from the Institute of Himalayan Bioresource Technology, ginkgolides J and A changed significantly with altitude, while the other compounds stayed more or less the same. The total amounts did not change significantly with the time of collection.

Harvest month and soil

Lin and colleagues (2020) collected leaves in different months and places in Zhejiang province, China. They found that temperature and rainfall had no significant effect on the main compounds, but the type of soil and its manganese and zinc content did. For Zhejiang, they concluded that October was the proper harvest time. The Indian study above, by contrast, found no significant change with the time of collection, so the two studies do not agree on whether harvest time matters.

Other factors compared

Ginkgo has separate male and female trees. Shi and colleagues compared leaves by origin, tree age, harvest time, the sex of the tree and processing method. Their abstract gives the overall range shown in the table but does not say which of these factors mattered most.

The limits of these data: all samples come from China or India, and the studies used different methods. They show how much the amounts can vary, not how much is in ginkgo sold in Thailand. No Thai study of ginkgo leaf content was found.

What is in the ginkgo seed (pae kuai)?

The seed is the part eaten as food. Its best-known safety concern is ginkgotoxin, the name for 4'-O-methylpyridoxine (C9H13NO3) and its glucoside. Its structure is close to that of vitamin B6, and researchers describe it as an anti-vitamin B6.

How much ginkgotoxin is in the seed?

Gong and colleagues (2018), at Nanjing Forestry University in China, measured ginkgotoxin compounds in seeds from three trees through the growing season. The total peaked at the mature stage, at 249.30, 295.62 and 267.85 µg per gram in the three samples. The cultivar had a larger influence on the amount than the age of the tree.

Does cooking change it?

Kong and colleagues (2026) heated ginkgotoxin with water in the laboratory. It broke down into pyridoxine and methanol; at 180 °C, half of the 4'-O-methylpyridoxine was gone in 10.0 minutes and half of its glucoside in 7.1 minutes. This was mainly a laboratory study of the compound heated in water, with a check in whole seeds; it does not show how much remains in seeds cooked at home. NCCIH notes that serious side effects have also occurred in people who ate roasted seeds.

Is there a recommended daily amount of ginkgo?

No. Ginkgo is not a nutrient, so it has no value in the Thai Reference Daily Intakes (Thai RDIs), which cover nutrients such as vitamins and minerals. As shown above, the amounts in the leaf also vary widely from batch to batch.

Who should be careful with ginkgo?

People who are pregnant or breastfeeding

NCCIH says ginkgo may be unsafe during pregnancy and that, if used near the time of delivery, it might cause early labour or extra bleeding. Little is known about whether it is safe while breastfeeding. Memorial Sloan Kettering also says the safety of ginkgo leaf during breastfeeding is not known.

People taking regular medication or other herbs

NCCIH says ginkgo may increase the risk of bleeding in people taking medicines that make blood clot less easily. The Drug Information Center at Mahidol University's Faculty of Pharmacy adds that using ginkgo together with some other herbs, including garlic, ginseng and dong quai, may also raise the chance of bleeding. Anyone taking regular medication should speak to a doctor or pharmacist.

Effects that can occur

NCCIH lists dizziness, stomach and gut symptoms and headache as the most common side effects. The Mahidol Drug Information Center lists nausea, vomiting, diarrhoea and headache.

Eating the seeds

NCCIH states that fresh ginkgo seeds are toxic when eaten, and that serious side effects have also occurred in people who ate roasted seeds.

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