Ginkgo biloba, Ginkgo
A beautiful coniferous tree with fan-shaped leaves and a lengthy tradition of use in Asia, now recognised for its help to treat anxiety, poor circulation and dementia.
scientific name Ginkgo biloba L.
family Ginkgoaceae
alternate names Maidenhair tree
parts used Leaves
A ginkgo tree bearing fruit in Bordeaux, France
Description
A deciduous conifer tree growing up to 30m tall and 9m wide, having glossy green fan-shaped leaves with irregularly toothed upper margins. The ginkgo is regarded as a living fossil, related to tree ferns and cycads. Trees are dioecious and may be male or female; male specimens are said to be upright and irregular while females are lower and spreading. Flowers are inconspicuous and appear after 20-35 years. Yellow/orange plum-like seeds about 2cm long are edible and can be roasted but the fleshy coat does deteriorate and smell similar to rancid butter due to its butyric acid content.
Habitat
The ginkgo is a native of China, growing in silty soils along stream banks, but is endangered in the wild. It is widely grown in Europe and America, introduced in the UK in 1754.1
Related plants
The ginkgo is the sole survivor of an ancient tree family. ‘Fastigiata’ is a columnar form; ‘Pendula’ has spreading or weeping branches.
Cultivation and harvest
The ginkgo tree can grow in a wide range of soils, preferring deep fairly rich soil with a neutral pH2 and full sun. It can tolerate drought and pollution, but does best in moist and well-drained soil. It is hardy to USDA zone 5a (UK zone 4) and does not need frost protection. Ginkgo is a relatively slow-growing tree, averaging less than 30cm per year, reaching 10m in 30 years. It can be readily coppiced or pruned, and this is best done while dormant in January or February. Ginkgo can be pot grown, in a well-drained container, using good quality multipurpose compost with 10% grit added. Keep moist and a little mulch can be added to the surface of the soil in spring.
Pests and diseases
Ginkgo has few pests or diseases.
Propagation
Collect ginkgo fruits in October and remove the pulp. The fresh seed is warm stratified for 1-2 months and then cold stratified for 1-2 months. The seed can be sown outside for spring germination in a moist seedbed. Cuttings taken in July root well.
Harvesting
The leaves are harvested in late summer not long before they start to turn yellow, and can be dried for later use. Whole branches can be removed for stripping of leaves. Drying should be done in a single layer or with regular turning to avoid the leaves sticking together.
Dried leaves of ginkgo
Therapeutic use
Traditional
Ginkgo has longstanding use in Asia, particularly for the seeds, which have been used as an aid to digestion and to reduce alcohol intoxication. The leaves were recorded for external use in a text of 1436 during the Ming dynasty, and then for internal use for diarrhoea in 1505. In traditional Chinese medicine, ginkgo is used for respiratory problems (asthma and bronchitis), brain disorders and urinary conditions.
Medicinal actions
Antihypoxic (increases peripheral and cerebral blood flow), anti-oxidant, cardiovascular tonic, anticoagulant and vasodilator. Uses of ginkgo are primarily indicated in poor circulation and in age-related cognitive impairment.3
Clinical applications and research
Almost all research on ginkgo has been performed with a German standardised extract known as EGb 761 or GBE, which is analytically controlled to 6% terpene lactones and 24% flavone glycosides. Studies have found evidence of improvements in circulation to the eye and brain4 and decreases in intermittent claudication (poor circulation in legs). A double-blind placebo-controlled trial using doses of 240mg and 480mg of the standardised extract over four weeks found a significant decrease in anxiety in patients with anxiety disorders.5 Studies have also considered possible benefits in dementia, memory and tinnitus.6 The broad spectrum of medicinal activities of ginkgo make it useful for an extremely wide range of chronic degenerative conditions.7
Sample preparations and dosage
Leaf tincture 2-5ml three times daily. Dried leaf infusion or powder in capsules, 6-12g per day.
A young ginkgo tree
Constituents and commerce
Key constituents
The leaves contain flavonoids including flavonol glycosides (including quercitin, kaempferol), biflavones, diterpenes (including terpene lactones), triactonic diterpenes (including ginkgolides A, B, C, J, M), the sesquiterpene bilobalide, and other organic acids and tannins.8 The maximum active terpenoid ingredients are found in late summer and early autumn, then declining until leaf fall.
Commerce
For medicinal use, leaves are harvested from trees of 2m or higher planted at a spacing of 3-6m. The leaves are dried in drum dryers and yields are 2-4 tons of dried leaves per hectare depending on site.9 World supplies of ginkgo come from plantations in the US, Japan, Korea, France and China. Ginkgo is commercially cultivated in plantations of up to 25,000 plants per hectare, where a row cultivation technique is used keeping the plants cut to 30cm in autumn, harvesting the leaves in late summer. Intensive growing can attain leaf yields of 20 tons per hectare after three years.10 Ginkgo leaf extract is now a widely sold supplement throughout the world, particularly for circulatory and cognitive disorders. Manufacturers’ preparations may vary, but most are standardised. However, there is concern about adulteration of ginkgo products with cheaper substitutes such as buckwheat or pea family ingredients as one study showed that 33 out of 35 products did not have the recommended levels of key ingredients.11
Safety
Tolerance of ginkgo extract is excellent and side effects minimal. The commonest problems are gastrointestinal upset, dizziness and headache. There have been isolated reports of adverse effects of bleeding when used alongside antiplatelet drugs so caution is needed in using ginkgo alongside anticoagulant medication.12 For safety, ginkgo should be discontinued at least two weeks before having dental or surgical treatment.
1 Hillier J and Lancaster R. (eds) (2014) The Hillier Manual of Trees and Shrubs. Eighth ed. London: Royal Horticultural Society, p489.
2 Laurain D. (2003) Cultivation of Ginkgo biloba on a large scale. In: VanBeek TA (ed) Ginkgo biloba, Boca Raton: CRC Press, pp68-88.
3 Committee on Herbal Medicinal Products (HMPC). (2015) European Union Herbal Monograph on Ginkgo biloba L., folium, London: European Medicines Agency.
4 Wu Y, Li S, Cui W, et al. (2007) Ginkgo biloba extract improves coronary blood flow in patients with coronary artery disease: Role of endothelium-dependent vasodilation. Planta Med 73: 624-628.
5 Woelk H, Arnoldt K, Kieser M, et al. (2007) Ginkgo biloba special extract Egb 761 in generalized anxiety disorder and adjustment disorder with anxious mood: A randomized, double-blind placebo-controlled trial. J Psychiatr Res 41: 472-480.
6 Brondino N, De Silvestri A, Re S, et al. (2013) A systematic review and meta-analysis of Ginkgo biloba in neuropsychiatric disorders: From ancient tradition to modern-day medicine. Evid Based Complement Alternat Med 2013: 915691; Hashiguchi M, Ohta Y, Shimizu M, et al. (2015) Meta-analysis of the efficacy and safety of Ginkgo biloba extract for the treatment of dementia. J Pharm Health Care Sci 1: 14.
7 Ramassamy C, Longpré F and Christen Y. (2007) Ginkgo biloba extract (EGb 761) in Alzheimer’s disease: Is there any evidence? Curr Alzheimer Res 4: 253-262.
8 Busia (2016) vol 2, p147.
9 Greenfield J and Davis JM. (eds) (2004) Medicinal Herb Production Guide: Ginkgo (Ginkgo biloba L.), North Carolina: Consortium on Natural Medicines and Public Health.
10 Crawford M. (2015) p87.
11 Booker A, Frommenwiler D, Reich E, et al. (2016) Adulteration and poor quality of Ginkgo biloba supplements. J Herb Med 6: 79-87; Gafner S. (2016) Ginkgo extract adulteration in the global market: A brief review. HerbalGram 109: 58-59.
12 Williamson et al. (2009) p207.