Ginkgo biloba

Ginkgo biloba belongs to the botanical family of Ginkgoceae consisting of approximately 15 genera. The ginkgo tree, known to be among the oldest living species on this planet, has flourished in forests for more than 200 million years, hence it is called a “living fossil”. The modern-day Ginkgo biloba has a very distinct appearance characterized by its fan-shaped leaves. They also live a very, very long time. A single Ginkgo biloba tree might drop its distinct fan-shaped leaves every year for centuries, if not millennia. As a ginkgo ages, it does not just survive, it thrives. Though 600-year-old ginkgos grow thinner annual rings, they are likely to pump out just as much defensive and immune-supporting chemicals as their younger relatives.

This tree having survived millions of years has developed a unique adaptability to thrive in even extremely polluted environments. This attribute has made the male ginkgos very popular in air polluted cities. Its resistance, adaptability, and regenerative strength is unsurpassed in the plant kingdom and it imparts this adaptogen quality to its user. Thus, it is medicinally considered an adaptogen remedy. It is a dioecious tree with the male and female reproductive organs on separate trees. The name ginkgo comes from the Chinese words sankyo or yinkuo, which means a hill apricot or silver fruit, due to their apricot shaped mature fruits and yellow color.
It is cultivated around the world for its medicinal properties and aesthetic value.

Ginkgo biloba

Uses

Both the leaves and the nuts of this tree have been in use for the past several centuries in traditional Chinese medicine. In fact, the nuts are known to have a longer history of usage, being first mentioned in herbals in the Yuan dynasty [1280 to 1368 AD], published in 1350 AD.1 Thus, for over 5000 years, the seeds (nuts) have been used to treat pulmonary disorders (like asthma, cough, and enuresis), and bladder inflammation, while the leaves have been mainly used to treat heart and lung dysfunctions and skin infections. However, it was only in the last 30 to 50 years that the use of the ginkgo leaf and its standardized extracts have been used for cognitive ailments.

According to The German Commission E (a scientific advisory board of the Federal Institute for Drugs and Medical Devices), Ginkgo B. has three primary uses or indications:

(1) For symptomatic treatment of disturbed performance in organic brain syndrome within the regimen of a therapeutic concept in cases of dementia syndromes with the following principal symptoms: memory deficits, disturbances in concentration, depressive emotional condition, dizziness, tinnitus, and headache. The primary target groups are dementia syndromes, including primary degenerative dementia, vascular dementia, and mixed forms of both.

(2) Improvement of pain-free walking distance in peripheral arterial occlusive disease in Stage II of Fontaine (intermittent claudication) and in a regimen of physical therapeutic measures, particularly walking.

(3) Vertigo and tinnitus (ringing in the ear) of vascular and involutional origin.

Studies have also shown positive results from the use of ginkgo for the following conditions: sexual dysfunction secondary to the use of selective serotonin reuptake inhibitors, mountain sickness and decreasing vasoactive response to cold, macular degeneration, asthma, and hypoxia.

The World Health Organization reiterated The Commission E approved uses noted above adding the following specific conditions to peripheral arterial occlusive disease: Raynaud’s disease, acrocyanosis, and post phlebitis syndrome.

Chemistry/Pharmacology

Ginkgo contains many different substances. Most of them fall into two categories Flavonoids and Terpenoids or Terpene lactones. Flavonoids are naturally occurring substances that function as antioxidants (scavenge free radicals-damaging compounds in the body that alter cell membranes, tamper with DNA, and even cause cell death) also found in fruits and vegetables. They enhance the immune system in the body and interfere with tumor formation. The type of flavonoid in Ginkgo is called Ginkgolide. Ginkgolides are unique compounds exclusive to Ginkgo and are broken down into separate ginkgolides A, B, C, J, and M. Each Ginkgolide has a different degree of potency. Ginkgolide B is considered the most active. Other flavonoids present are quercetin (which is one of the most studied flavonoids and is a stronger antioxidant than vitamin E), and kaempferol. Terpene lactones are the active constituents that give ginkgo a bitter strong flavor and helps increase blood circulation.

Other components present are Amino Acid-6hydrozykynurenic acid, Dimeric flavones (bilobetin, ginkgetin, isoginkgetin, scieadopitysin), Proanthocyanidins, ginkgolic acid, ascorbic acid, carotenoids, and Bilobalide.

The nuts contain essential oil, fatty acid, tannin, and resin.

Clinical Studies

Data suggest that ginkgo biloba exhibits protective effects in ischemic stroke. Li et. al showed that ginkgo in combination with aspirin treatment alleviated cognitive and neurological deficits after acute ischemic stroke without increasing the incidence of vascular events. Therefore, the administration of G biloba is recommended after acute ischemic stroke.
Several animal studies have shown that ginkgo improves memory. However, human studies have been mixed in demonstrating that ginkgo improves memory and reduces cognitive decline. Some results confirm that the effects of gingko b. on aspects of cognition in asymptomatic volunteers are more pronounced for memory, particularly working memory. Wesnes et. al. showed a ginkgo/ginseng combination to significantly improve an Index of Memory Quality and demonstrated improvements to the memory of healthy middle-aged volunteers. Additionally, it has been shown to reduce tinnitus.
Some of the more promising studies of Ginkgo involve its positive effect in neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease.
Shakibaei et. al. has shown ginkgo biloba to be an effective complementary treatment for ADHD.
Moraga et. al, showed evidence supporting the use of ginkgo in the prevention of acute mountain sickness (AMS), thus demonstrating that 24 hours of pretreatment with ginkgo.
Ginkgo biloba and subsequent maintenance during exposure to high altitude are sufficient to reduce the incidence of AMS in participants with no previous high-altitude experience.
Ye et. al have shown data to suggest ginkgo may reduce ovarian cancer risk.

Biomechanical Mechanism

The mechanism of action of ginkgo is produced by its functions as a neuroprotective agent, an antioxidant, a free-radical scavenger, a membrane stabilizer, and an inhibitor of platelet-activating factor via the terpene ginkgolide B. Other pharmacologic effects include the following: endothelium relaxation mediated by inhibition of 3',5'-cyclic GMP (guanosine monophosphate) phosphodiesterase; inhibition of age-related loss of muscarinergic cholinoceptors and α-adrenoceptors; and stimulation of choline uptake in the hippocampus. Ginkgo extract also has been shown to inhibit beta-amyloid deposition, thus suggested in Alzheimer’s disease.
Ginkgo interacts with several cytochrome P450 enzymes. Pretreatment with G. biloba extract induces expression of CYP3A proteins and mRNA and increases CYP3A activity. It also inhibits CYP2B6 catalytic activity and bupropion hydroxylation. Ginkgo may play a role in decreasing high-glucose-induced endothelial inflammation via inhibition of interleukin-6 activation, and repeated intake of ginkgo enhanced cell proliferation and neuroblast differentiation. Flavonoids present in ginkgo extracts inhibited estrogen biosynthesis via aromatase inhibition, decreased CYP19 mRNA, and induced transcriptional suppression.
Chemopreventive properties of bilobalide, a terpene trilactone, may occur via alterations in cryptal cell proliferation and drug-metabolizing enzyme activities. Exocarp polysaccharides from ginkgo affected expression of c-myc, bcl-2 and c-fos genes, which can inhibit proliferation and induce apoptosis and differentiation of human gastric tumor cells.

Sources/Articles

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