Medicinal Value and Side Effects of Ginkgo Nuts (Seeds of Ginkgo biloba)

Doctor zhou
The ginkgo (Ginkgo biloba) is an ornamental plant found throughout China. Each autumn, when its leaves turn yellow, cities gain a striking scenic sight. Wild ginkgo grows mainly in the natural forests of Tianmu Mountain, at elevations of 500–1000 m on acidic, well-drained soil. Ginkgo fruit ripens in the seventh and eighth lunar months and falls naturally to the ground; some people gather it to sell to herb dealers, while others take it home for their own use. Ginkgo nuts have a long history as medicine. The official pharmacopoeia of the Southern Song, Shaoxing Bencao, was the first to list ginkgo nuts, recording: "Ginkgo... is produced in many places; only those from Yizhou that are large are fine. The fruit is gathered in the seventh and eighth months and sun-dried. Because its color is like silver and its shape like a small apricot, it is so named."
The ginkgo is a very unusual plant; botanists place it alone in its own class, order, family, genus, and species. It is called the panda and the living fossil of the plant world. Ginkgo retains many primitive features; its leaf venation is "dichotomously branched," unique among gymnosperms but common in ferns. When its male pollen germinates, it produces only two ciliated, motile sperm— a feature found among gymnosperms only in cycads, yet common in ferns. This shows ginkgo to be a more ancient plant than pines, firs, and cypresses. We rarely see ginkgo flower, but Compendium of Materia Medica (Bencao Gangmu) records: "(Ginkgo) flowers in clusters in the second month, blue-white; it blooms at the second watch and immediately falls, so that people rarely see it."
Bai guo (ginkgo nut) is the kernel of the ginkgo fruit, so the ginkgo tree is often called the white-fruit tree. Ginkgo nut is the white kernel left after the fleshy fruit coat is removed. TCM uses it as a cough-suppressing and anti-asthmatic herb; it also treats frequent urination, and can achieve nearly 100% efficacy for senile frequent urination. However, ginkgo nuts are toxic, and overeating can cause poisoning, with especially marked side effects in children. Riyong Bencao records: "Eating too much obstructs qi and provokes wind; children who eat too much become giddy, convulse, and induce gan (infantile malnutrition); eaten with eel it causes soft wind." Sui Xiju Yinshi Pu records: "Those poisoned by it (ginkgo nuts) become dizzy as if drunk; ginkgo shell or the head of a dried white croaker, decocted, counteracts it. If eaten to excess, it may even be fatal; the prudent should know this."
Because many people in folk medicine do not understand the toxicity of ginkgo nuts when eating them, ginkgo nut poisoning occurs from time to time, especially in children. It is generally caused by overeating or eating raw nuts, with a latent period of 1–12 hours. Common symptoms of ginkgo nut poisoning include nausea, vomiting, abdominal pain, diarrhea, and loss of appetite; severe symptoms may include restlessness, fear, convulsions, limb rigidity, opisthotonus, spasms, limb weakness, paralysis, and difficulty breathing, and severe cases can be fatal. Adults who overeat may also develop severe convulsions. The juice of ginkgo's outer seed coat is also highly irritating to the skin; ginkgotoxin contained in ginkgo nuts can also cause poisoning through skin contact. After percutaneous absorption it is excreted through the intestine and kidneys and can cause enteritis and nephritis. Therefore, when harvesting and eating ginkgo nuts we must protect ourselves and keep them out of children's reach. Because ginkgo nut poisoning can be fatal, victims must be rushed to hospital immediately; do not try to detoxify at home.
TCM holds that ginkgo nuts astringe the lung and calm asthma, and check vaginal discharge and reduce urination. They are used mainly for asthma and cough, leukorrhea and turbid discharge, seminal emission and frequent urination, unexplained swellings and toxins, and ringworm sores. The usual internal dose as a decoction is 3–9g. They may also be pounded for juice and applied externally, or sliced and rubbed on ringworm sores. The LD50 (intraperitoneal in mice) of the water-soluble component of ginkgo's outer seed coat is about 5 g/kg, so adults using fully ripe ginkgo nuts at ordinary doses will generally not be poisoned.
There are reports of using ginkgo nuts 30g and 10 jujubes, one dose daily decocted in water, to treat frequent urination in the elderly; effect appeared within 3 days, and of 10 cases treated, all were cured. There are also reports of grinding 250g ginkgo nuts into fine powder, adding 20g borneol and 400ml of 60% ethanol, steeping in a 500ml glass vessel for 24 hours, then rubbing the face; during treatment all cosmetics are forbidden. This treats acne with a cure rate as high as 89%. Ginkgo nuts for ringworm sores of the head and face are also recorded in antiquity; for example, in the Sha's Jingyan Fang, a formula for head and facial ringworm uses raw ginkgo kernel cut open and rubbed frequently on the affected area.
In Shoushi Baoyuan there is an ointment formula called Ginkgo Paste that treats chronic cough with sputum that has lasted for years. It uses 4 taels of aged fine tea (lightly roasted and ground to fine powder), 4 taels of ginkgo nut (half with the red skin removed, half with the white skin removed, mashed), 4 taels of walnut meat (mashed), and half a jin of honey, simmered together in a pot into an ointment, taken at any time.
Diannan Bencao records that ginkgo nuts steamed with glutinous rice and made into honey pills, taken together with walnut meat, can treat dysphagia and stomach reflux, turbid leukorrhea, and cold strangury. It also records that ginkgo nuts mashed and applied to the temples treat headache (tou feng) and eye pain.
Modern pharmacology confirms that ginkgo nuts have a expectorant effect on the respiratory system; they also lower blood pressure and improve cerebral ischemia and can be used to treat ischemic stroke, although ginkgo-leaf extract capsules are more commonly used for cerebral thrombosis. In addition, ginkgo nuts have immunosuppressive and anti-allergic effects and can be used to treat allergies, as well as antimicrobial and anti-aging effects. But given ginkgo nuts' certain toxicity, use should follow a physician's advice; self-medication by patients is not recommended.

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