Ginkgo

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Ginkgo biloba
A ginkgo leaf
A ginkgo leaf
Scientific classification
Domain: Eukaryota
Kingdom: Plantae
Phylum: Ginkgophyta
Class: Ginkgoopsida
Family: Ginkgoaceae
Genus: Ginkgo
Species: G. biloba

Ginkgo (or maidenhair) is the common name for the tree Ginkgo biloba.

The Ginkgo family first appeared 200 to 225 million years ago[1], in the Paleozoic era. Ginkgoes were widespread about 100 million years ago, but now they only exist in a wild state in a remote region in China. However, they have been widely exported to the rest of the world as an ornamental tree, where ginkgoes are also known as "maidenhair" trees[1]. The ginkgo is the only living member of its phylum.

Ginkgoes are unique in the plant kingdom, as evidenced by their sole membership of the Ginkgophyta phylum. For one thing, they are possibly the only plants to have centrioles. Ginkgoes represent the only extant link between lower and higher plants because of their method of fertilization, which involves swimming sperm[1].

Ginkgoes are dioecious, though the two sexs are similar in morphology until about 30 years old[1]. Among other identifying characteristics, female trees develop edible but foul-smelling seeds in the autumn[2]. In the spring, older ginkgoes will develop sporangia.They are a resilient species, able to withstand city pollution and fungus and insect attacks[1]. One ginkgo in Hiroshima, Japan even managed survive the atomic blast that leveled much of the city in World War II[3].

Clinical role

Ginkgoes may have medical applications. The extract EGb 761has also been used to treat hearing problems, impotence, circulatory problems, and oxygen deprivation[3].

Ginkgo biloba does not prevent dementia according to a large randomized controlled trial[4] and systematic review[5] by the Cochrane Collaboration.

Selected trials of gingko for dementia[6][7][4]
  Patients Intervention Outcome
North American EGb Study Group:[6]
1997
309 patients with mild to severe dementia 120 mg/d beneficial
Solomon:[7]
2002
203 "healthy adults older than 60 years with Mini-Mental State Examination scores greater than 26 40 mg 3 times per day not beneficial
GEM:[4]
2008
3069 "community volunteers aged 75 years or older with normal cognition or mild cognitive impairment" 120 mg twice daily not beneficial

References

  1. 1.0 1.1 1.2 1.3 1.4 Hori, T., Ridge, R.W., Tulecke, W., Del Tredici, P., Trémouillauw-Guiller, J., and H. Tobe. (1997). Preface. In Hori, T. et al (Eds.), Ginkgo biloba, a global treasure: from biology to medicine. New York: Springer-Verlag. pp. vii-ix.
  2. Soma, S. Development of the female gametophyte and the embryogeny of Ginkgo biloba. (1997). In Hori, T. et al (Eds.), Ginkgo biloba, a global treasure: from biology to medicine. New York: Springer-Verlag. pp. 51-65.
  3. 3.0 3.1 Gorman, C. (1997). More than a funny name. Time. November 3, p. 53.
  4. 4.0 4.1 4.2 DeKosky ST, Williamson JD, Fitzpatrick AL, et al (November 2008). "Ginkgo biloba for prevention of dementia: a randomized controlled trial". JAMA 300 (19): 2253–62. DOI:10.1001/jama.2008.683. PMID 19017911. Research Blogging.
  5. Birks J, Grimley Evans J (2009). "Ginkgo biloba for cognitive impairment and dementia". Cochrane Database Syst Rev (1): CD003120. DOI:10.1002/14651858.CD003120.pub3. PMID 19160216. Research Blogging.
  6. 6.0 6.1 Le Bars PL, Katz MM, Berman N, Itil TM, Freedman AM, Schatzberg AF (1997). "A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. North American EGb Study Group". JAMA 278 (16): 1327–32. PMID 9343463[e]
  7. 7.0 7.1 Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R (2002). "Ginkgo for memory enhancement: a randomized controlled trial". JAMA 288 (7): 835–40. PMID 12186600[e]