Ginkgo is the oldest living tree species on the earth, dating back to the time of the dinosaurs.It is native to northeast Asia. Medically its leaves used to prevent slow memory loss associated with aging. It has various other medical uses.
A folk etymology for the word says that, the Japanese characters used to write ginkgo look as though they could be read ginkyÅ, and this was the name Engelbert Kaempfer, the first Westerner to see the species in 1690, wrote down in his Amoenitates Exoticae (1712). However, his y was misread as a g, and the misspelling stuck
The Ginkgo (Ginkgo biloba; in Chinese), frequently misspelled as “Gingko”, and also known as the Maidenhair Tree, is a unique tree with no close living relatives. It is classified in its own division, the Ginkgophyta, comprising the single class Ginkgoopsida, order Ginkgoales, family Ginkgoaceae, genus Ginkgo and is the only extant species within this group. It is one of the best known examples of a living fossil. In the past it has also been placed in the divisions Spermatophyta or Pinophyta. Ginkgo is a gymnosperm: its seeds are not protected by an ovary wall. The apricot-like structures produced by female ginkgo trees are technically not fruits, but are the seeds having a shell that consists of a soft and fleshy section (the sarcotesta), and a hard section (the sclerotesta).
For centuries it was thought to be extinct in the wild, but is now known to grow in at least two small areas in Zhejiang province in eastern China, in the Tian Mu Shan Reserve. However, ginkgo trees in these areas may have been tended and preserved by Chinese monks for over 1000 years. Therefore, whether native ginkgo populations still exist is uncertain
Ginkgos are medium-large deciduous trees, normally reaching a height of 20â€“35 m (66-115 feet), with some specimens in China being over 50 m (164 feet). The tree has an often angular crown and long, somewhat erratic branches, and is usually deep rooted and resistant to wind and snow damage. Young trees are often tall and slender, and sparsely branched; the crown becomes broader as the tree ages. During autumn, the leaves turn a bright yellow, then fall, sometimes within a short space of time (1â€“15 days). A combination of resistance to disease, insect-resistant wood and the ability to form aerial roots and sprouts makes ginkgos very long-lived, with some specimens claimed to be more than 2,500 years old: A 3,000 year-old ginkgo has been reported in Shandong province in China (Lewington and Parker, 183).
Some old Ginkgos produce aerial roots, known as chichi (Japanese; “nipples”) or zhong-ru (Chinese), which form on the undersides of large branches and grow downwards. Chichi growth is very slow, and may take hundreds of years to occur. The function, if any, of these thick aerial roots is unknown.
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Ginkgo branches grow in length by growth of shoots with regularly spaced leaves, as seen on most trees. From the axils of these leaves, “spur shoots” (also known as short shoots) develop on second-year growth. Short shoots have very short internodes (so that several years’ growth may only extend them by a centimeter or two) and their leaves are ordinarily unlobed. They are short and knobby, and are arranged regularly on the branches except on first-year growth. Because of the short internodes, leaves appear to be clustered at the tips of short shoots, and reproductive structures are formed only on them (see picture to above leftâ€” seeds and leaves are visible on short shoots). In Ginkgos, as in other plants that possess them, short shoots allow the formation of new leaves in the older parts of the crown. After a number of years, a short shoot may change into a long (ordinary) shoot, or vice versa.
The leaveslare unique among seed plants, being fan-shaped with veins radiating out into the leaf blade, sometimes bifurcating (splitting) but never anstomosing to form a network. Two veins enter the leaf blade at the base and fork repeatedly in two; this is known as dichotomous venation. The leaves are usually 5-10 cm (2-4 inches), but sometimes up to 15 cm (6 inches) long. The old popular name “Maidenhair tree” is because the leaves resemble some of the pinnae of theMaidenhair fern Adiantum capillus-veneris.
Leaves of long shoots are usually notched or lobed, but only from the outer surface, between the veins. They are borne both on the more rapidly-growing branch tips, where they are alternate and spaced out, and also on the short, stubby spur shoots, where they are clustered at the tips. During summer the leaves are a deep green, turning to brilliant yellow in the autumn. They generally remain yellow for a time, then suddenly drop most of their leaves in a short period.
The extract of the Ginkgo leaves contains flavonoid glycosides and terpenoids (ginkgolides, bilobalides) and has been used pharmaceutically. It has many alleged nootropic properties, and is mainly used as memory enhancer and anti-vertigo agent. However, studies differ about its efficacy. Some controversy has arisen over the conclusions drawn by some studies that were allegedly funded by a firm which marketed Ginkgo. Slate, an Internet-based magazine owned by The Washington Post Company, reported in April 2007:
Ginkgo biloba has been used medicinally for thousands of years. Today, it is one of the top selling herbs in the United States.
Ginkgo is used for the treatment of numerous conditions, many which are under scientific investigation. Available evidence demonstrates ginkgo’s efficacy in the management of intermittent claudication, Alzheimer’s/multi-infarct dementia, and “cerebral insufficiency” (a syndrome thought to be secondary to atherosclerotic disease, characterized by impaired concentration, confusion, decreased physical performance, fatigue, headache, dizziness, depression, and anxiety).
Although not definitive, there is promising early evidence favoring use of ginkgo for memory enhancement in healthy subjects, altitude (mountain) sickness, symptoms of premenstrual syndrome (PMS), and reduction of chemotherapy-induced end-organ vascular damage.
Although still controversial, a recent large trial has shifted the evidence against the use of ginkgo for tinnitus.
The herb is generally well tolerated, but due to multiple case reports of bleeding, should be used cautiously in patients on anti-coagulant therapy, with known coagulopathy, or prior to some surgical or dental procedures.
In 2002, a long-anticipated paper appeared in JAMA (Journal of the American Medical Association) titled “Ginkgo for memory enhancement: a randomized controlled trial.” This Williams College study, sponsored by the National Institute on Aging rather than Schwabe, examined the effects of ginkgo consumption on healthy volunteers older than 60. The conclusion, now cited in the National Institutes of Health’s ginkgo fact sheet, said: “When taken following the manufacturer’s instructions, ginkgo provides no measurable benefit in memory or related cognitive function to adults with healthy cognitive function.”
Dr. Willmar Schwabe GmbH & Co. is a German pharmaceutical company that markets a Ginkgo product within the United States.
Out of the many conflicting research results, Ginkgo extract seems to have three effects on the human body: it improves blood flow (including microcirculation in small capillaries) to most tissues and organs; it protects against oxidative cell damage from free radicals; and it blocks many of the effects of PAF (platelet aggregation, blood clotting) that have been related to the development of a number of cardiovascular, renal, respiratory and CNS (Central Nervous System) disorders. Ginkgo can be used for intermittent claudication.
A 2004 conference paper summarizes how various trials indicate that Ginkgo shows promise in the treatment of Alzheimer’s disease, although further study is needed.
Ginkgo is commonly added to energy drinks, but the amount is typically so low it does not produce a noticeable effect, except perhaps via a placebo effect from Ginkgo being listed on the label.Ginkgo supplements are usually taken in the range of 40â€“200 mg per day.
Ginkgo may have some undesirable effects, especially for individuals with blood circulation disorders and those taking anti-coagulants such as aspirin and warfarin, although recent studies have found that ginkgo has little or no effect on the anticoagulant properties or pharmacodynamics of warfarin. Ginkgo should also not be used by people who are taking monoamine oxidase inhibitors (MAOI) or by pregnant women without first consulting a doctor.
What the Science Says
Numerous studies of ginkgo have been done for a variety of conditions. Some promising results have been seen for Alzheimer’s disease/dementia, intermittent claudication, and tinnitus among others, but larger, well-designed research studies are needed.
Some smaller studies for memory enhancement have had promising results, but a trial sponsored by the National Institute on Aging of more than 200 healthy adults over age 60 found that ginkgo taken for 6 weeks did not improve memory.1
NCCAM is conducting a large clinical trial of ginkgo with more than 3,000 volunteers. The aim is to see if the herb prevents the onset of dementia and, specifically, Alzheimer’s disease; slows cognitive decline and functional disability (for example, inability to prepare meals); reduces the incidence of cardiovascular disease; and decreases the rate of premature death.
Ginkgo is also being studied by NCCAM for asthma, symptoms of multiple sclerosis, vascular function (intermittent claudication), cognitive decline, sexual dysfunction due to antidepressants, and insulin resistance. NCCAM is also looking at potential interactions between ginkgo and prescription drugs.
Side Effects and Cautions
Side effects of ginkgo may include possible increased risk of bleeding, headache, nausea, gastrointestinal upset, diarrhea, dizziness, or allergic skin reactions. More severe allergic reactions have occasionally been reported. If any side effects are experienced, consumption should be halted immediately.
There are some data to suggest that ginkgo can increase bleeding risk, so people who take anticoagulant drugs, have bleeding disorders, or have scheduled surgery or dental procedures should use caution and talk to a health care provider if using ginkgo.
Uncooked ginkgo seeds contain a chemical known as ginkgotoxin, which can cause seizures. Consuming large quantities of seeds over time can cause death. Ginkgo leaf and ginkgo leaf extracts appear to contain little ginkgotoxin.
It is important to inform your health care providers about any herb or dietary supplement you are using, including ginkgo. This helps to ensure safe and coordinated care.
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The information presented herein by is intended for educational purposes only.Individual results may vary, and before using any supplements, it is always advisable to consult with your own health care provider.
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