Ginkgo Biloba: Traditional Use, Constituents and Evidence

Two-hundred-and-seventy million years. That's roughly how long Ginkgo biloba has been on this planet , pre-dating the dinosaurs, outlasting at least five mass extinction events, and still turning up in neat rows along the footpaths of Adelaide's North Terrace. I walk past a pair of them most weeks on the way to the State Library, and every autumn, when the leaves go that unmistakable waxy gold, I think about how strange it is that we're still arguing about what they do.

The short version is: ginkgo's chemical profile is genuinely interesting, its traditional history runs deep, and its clinical evidence base is real but far messier than the supplement aisle suggests. Let me unpack that properly.

A living fossil with a long paper trail

Ginkgo biloba is the sole surviving species of the division Ginkgophyta , a relic lineage with no close living relatives. The tree was cultivated in Chinese temple gardens for centuries before Western botanists encountered it; its leaves and seeds appear in Chinese materia medica texts dating back at least to the 15th century, with some historians tracing references further. The seeds (bai guo) were used in traditional Chinese medicine for lung-related presentations, whilst the leaf was employed for circulatory complaints , although the standardised leaf extract we now associate with research is a 20th-century development, not something an 18th-century herbalist would have recognised.

It arrived in Europe around 1730, initially as a botanical curiosity. The German physician and botanist Engelbert Kaempfer described it formally after encountering it in Japan. It would take another two centuries before pharmaceutical-grade extraction processes were developed in Europe; predominantly in Germany, to produce the concentrated leaf extracts that entered clinical trials from the 1960s onward.

Key constituents: what's actually in the leaf

The chemistry of ginkgo leaf is dominated by two classes of compound: flavonoid glycosides and terpene trilactones.

The flavonoid fraction includes quercetin, kaempferol, and isorhamnetin derivatives, compounds found across many plants, but present in ginkgo in a specific and concentrated profile. The terpene trilactones are more distinctive: ginkgolides A, B, C, and J, and bilobalide. Ginkgolide B in particular has attracted significant research attention for its role as a platelet-activating factor (PAF) antagonist; meaning it appears to interfere with PAF receptor binding in laboratory models.

Worth knowing: the terpene backbone of ginkgolides is structurally unusual, and the biosynthetic pathway that produces them in the tree is still being mapped by phytochemists. Bilobalide is a sesquiterpene lactone with a cage-like structure not found in any other known plant genus. That kind of chemical singularity is part of what makes ginkgo interesting to researchers, and to people like me who got a bit obsessed with 19th-century botanical chemistry after finding a battered copy of Pereira's Elements of Materia Medica in a secondhand bookshop in Hahndorf years ago. Anyway.

Standardised extracts (the kind used in most clinical trials) are typically prepared to contain 24% flavonoid glycosides and 6% terpene trilactones. This matters because wild or unprocessed leaf material varies substantially in constituent concentration. For more on how this type of preparation works, our standardised extract glossary entry explains the methodology in context.

One note on safety chemistry: raw ginkgo seeds contain ginkgotoxin (4-O-methylpyridoxine), which can be toxic in quantity. This is why traditional preparations specified careful processing, and why most regulatory guidance focuses on leaf-based standardised extracts rather than seed preparations.

How ginkgo constituents interact with biological systems

This is where the research gets interesting, and where people sometimes start making claims the evidence doesn't fully support.

In laboratory and animal models, ginkgo flavonoids have demonstrated antioxidant activity, free-radical scavenging, and inhibition of certain oxidative pathways. The ginkgolides' PAF antagonism has been studied in the context of platelet aggregation. Bilobalide has been examined in models of neuronal cell function, with some in-vitro work suggesting interaction with GABA-A receptors.

Here's where I'd ask you to be careful with that last point. In-vitro findings; cells in a dish, don't automatically translate to effects in a living human. Bioavailability and first-pass metabolism shape what actually reaches target tissues, and for ginkgo constituents, the pharmacokinetic data (our pharmacokinetics entry covers this in more depth) suggests significant variability between individuals.

None of this means the compounds are inactive in vivo. It means the step from "we see X in a laboratory model" to "therefore this substance treats Y condition" is much longer and harder than marketing copy implies.

The clinical evidence: promising but patchy

Ginkgo has one of the larger bodies of clinical trial data of any botanical, there are hundreds of published studies. The challenge is quality and consistency, not volume.

The most cited area is cognitive function, particularly in older adults. Early meta-analyses showed modest positive signals in some populations. Then the large, rigorously designed Ginkgo Evaluation of Memory (GEM) study, published in JAMA in 2008, followed over 3,000 participants over six years and found no significant difference between a standardised ginkgo extract and placebo on rates of dementia or cognitive decline. This was a well-powered, randomised controlled trial; it deserves to be taken seriously.

Other areas of research include peripheral vascular function, tinnitus, and altitude acclimatisation. The evidence across these is mixed. The Cochrane Collaboration has published systematic reviews on ginkgo for cognitive impairment and dementia that describe "inconsistent and unconvincing" overall evidence, whilst acknowledging some individual trial data is positive. That's an honest read of a messy literature.

I'd argue the emphasis on ginkgo as a memory product in mainstream retailing has run well ahead of what the trial data can actually support. That's not unique to ginkgo, it's a recurring issue in botanical product marketing, but it's worth naming plainly.

Regulatory status in Australia

In Australia, ginkgo preparations are regulated by the Therapeutic Goods Administration (TGA) under the Therapeutic Goods Act 1989. Most products are listed on the Australian Register of Therapeutic Goods (ARTG) as Listed medicines (AUST L number); a category that permits claims based on traditional use or low-level evidence, provided claims are "permitted indications" from the TGA's approved list.

Listed medicines do not undergo the same pre-market efficacy assessment as Registered (AUST R) medicines. This means a product can appear on shelf with a listed number and an indication like "maintain/support healthy circulation" without that claim being independently verified by the TGA before listing. The TGA audits compliance after the fact. This is a legitimate regulatory pathway, but it's important context for understanding what an AUST L listing does and doesn't tell you.

Ginkgo is not a scheduled poison under the Poisons Standard. It's not restricted in the same manner as, say, kava (which has specific import controls under Australian Border Force regulations) or Schedule 4/8 substances. Standard leaf extract preparations are available over-the-counter. Manufacturing must comply with Good Manufacturing Practice (GMP) requirements. The phytomedicine regulatory framework here is more permissive than for pharmaceutical drugs, but it's not unregulated, the distinction matters.

For reference, the TGA's permitted indications list for ginkgo-containing products covers circulation-related and cognitive support claims. Any supplier making claims outside permitted indications, or failing to hold a valid ARTG listing, is in breach of the Act.

Interactions and safety signals

This section matters. Ginkgo's antiplatelet activity; the PAF antagonism noted above, means it may interact with anticoagulant medications. Several case reports and pharmacological reviews have flagged potential interactions with warfarin and aspirin; the clinical significance in individual patients depends on dose and co-administered agents. This is well enough established that most clinical pharmacology references recommend caution.

Ginkgo is also a moderate inhibitor of certain cytochrome P450 enzymes, particularly CYP2C19 and CYP3A4, pathways involved in metabolising a range of pharmaceutical drugs. Again, clinical significance varies, but it's not something to wave away.

People on prescription anticoagulants, antiplatelet therapy, or managing seizure disorders should discuss ginkgo use with their prescriber. That's not a blanket prohibition; it's the kind of drug-herb interaction awareness that should accompany any botanical product used alongside medication.

Sources

• Listed Medicines Evidence Guidelines; Therapeutic Goods Administration (TGA)
• DeKosky ST et al. (2008). Ginkgo biloba for Prevention of Dementia, JAMA (via PubMed/NCBI)
• Tan MS et al. (2015). Efficacy and Adverse Effects of Ginkgo biloba for Cognitive Impairment and Dementia, Journal of Alzheimer's Disease (via PubMed/NCBI)
• Permissible Indications for Listed Medicines; Therapeutic Goods Administration (TGA)

, Naomi Ellison, Botanical & phytomedicine writer

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