|
|
|
|
The results of numerous in-vitro and in-vivo
studies have shown Ginkgo biloba extract to
have a varied pharmacology and interesting
potential in the management of a range of
conditions (note Ginkgo biloba is an ingredient in PowerMate, Sunnie and Diabetiks):
Circulatory system
Ginkgo biloba extract is held to have a number
of vaso-protective actions including a relaxing
effect on blood vessels, a contractile action resulting in an increase of
tone in abnormally relaxed vessels, a protective action against
capillary permeability, antithrombotic activity as well as anti-ischemic
and anti-edemic properties.
Cognition and memory
Ginkgo biloba extract is believed to support both cognitive and
memory function. Studies suggest a range of pharmacological actions
including enhancement of neurotransmitter release, the inhibition of
biogenic amine uptake and a protection of endothelial derived factor
(EDRF) central mechanisms. Bilobalide contained in Ginkgo biloba
extract may also reduce ATP loss thus supporting cognition, memory
and over brain energy levels.
Platelet activating factor (PAF)
PAF is an inflammation mediator involved in various
pathophysiological conditions affecting heart, lung, brain and vessels
due to its potent chemotactic activity on neutrophils inducing
superoxide release, aggregation and degranulation. Ginkgolide B has
been found to be the most active PAF antagonist compound
contained in Ginkgo biloba extract (28,29,30) and is thought to be
effective in improving the blood rheology and microcirculation,
inhibiting super oxide generation and in modulating the effect of PAF
on vascular bed (28,31,32,33).
Activity on ageing and age-related disorders
Ginkgo biloba extract is believed to have a protective effect that may
guard against some of the effect of the ageing process. Animal
studies indicate that Ginkgo biloba extract may protect cerebellar
neurones against oxidative stress induced by hydrogen peroxide.
Pre-treatment of neurones with Ginkgo biloba was reported to
reduce cell death rate during the exposure to oxidative stress and to
defend against cell apoptosis and DNA fragmentation induced by
hydroxyl radicals (42,43). Peroxidation of LDL is one of the
mechanisms involved in the deposition of cholesterol in the arterial
wall and the consequent formation of the atherosclerotic plaque.
Ginkgo biloba is thought to protect LDL against oxidative stress
caused by superoxide, peroxyl and hydroxyl radicals (44).
It was also observed that the extract may be able to improve the
mitochondria respiration in gerbils with cerebral ischaemia and the
age-related learning deficits in rats and mice (46), moreover it was
also reported to improve the short-term memory in aged mice and to
reduce the age-related changes in membrane fluidity (47).
Anti-ischemic and cardio-protective activities.
Studies report that Ginkgo biloba has an activity on the cardiovascular system particularly at the level of the arteries, veins,
capillaries and cellular elements of the blood. On an isolated rat heart
Ginkgo biloba demonstrated an antiarrhythmic effect on
post-ischaemic arrhythmia and a protective action against cardiac
ischaemia-reperfusion oxidative injury by inhibition of oxygen free
radicals production during reperfusion and preventing the leakage
and oxidation of ascorbate - a myocardial endogenous antioxidant
(36,37).
The German Monograph - the clinically proven standard for
Ginkgo biloba
The extracts referred to in clinical trials on Ginkgo biloba are
manufactured using a multi-step process specifically designed to
concentrate the active principles from the Ginkgo biloba leaves.
Limits (both upper and lower) are defined in the German
Monograph.
Ginkgo biloba extract should contain approximately 24%
flavonglycosides (primarily composed of quercetin, kaempferol, and
isorhamnetin) and 6% terpene lactones (min 2.8 - max 3.4%
ginkgolides A, B, and C, and min 2.6- max 3.2% bilobalide). Other
constituents include proanthocyanadins, glucose, rhamnose, organic
acids (hydroxykinurenic, kynurenic, protocatechic, vanillic, shikimic),
D-glucaric acid and ginkgolic acid (max 5 ppm), and related
alkylphenols .
Antioxidant and free radical scavenger
Free radical scavenger
The free radical scavenging activity of Ginkgo biloba is most likely
due to the flavonoid constituents of the extract. Ginkgo biloba
protects endothelial cells against the negative effects of oxygen
produced by the hypoxanthine/xanthine oxidase system by inhibiting
the lipid peroxidation and by preventing the decrease of intracellular
glutathione. The extract is thought to have a behaviour similar to a
superoxide dismutase, scavenging superoxide anion (18).
Ginkgo biloba is also thought to be able to inhibit the oxygen radical
production by human polymorphonuclear neutrophils activated by
bacterial chemotactic peptide or by type I collagen (19).
Antioxidant
The antioxidant activity of Ginkgo biloba has also been demonstrated
on the membrane micro-rheological changes and on lipoperoxidation
induced by exposure of human erythrocytes to hydrogen peroxide
(20,21). Many other studies also demonstrate the antioxidant activity
and the scavenger effect on free radicals possessed by Ginkgo biloba
extract (22-27).
Ginkgo biloba
Ginkgo Biloba is extracted from the leaves of the
Ginkgo Biloba tree dating from the Palaeozoic era (350 million years
ago). The Ginkgo Biloba tree, which is notable for high resistance to
both pollutants and pests, has a long tradition of use in Oriental
medicine; in particular for the treatment and control of respiratory
and circulatory ailments and for brain function.
The name Ginkgo is derived from a wrong transcription of the
Japanese name Yin-Kwo that means silver fruit, while the name
biloba derives from the bilobed shape of its leaf (1).
Cosmetic applications
Cosmoceutical applications include anti-ageing, elimination of toxins,
free radical scavenger, powerful antioxidant, strengthening of the
skins defences, improvement of dermal micro-circulation and
stimulation of lymph drainage. Among the range of products currently
marketed are face creams, anti-ageing creams, anti-wrinkle creams,
shampoo, anti-cellulite preparations and toothpaste.
As some rare occurrences of skin sensitivity to the terpene lactones
of Ginkgo biloba have been observed
|
| |
|
|
| |
|
|
|
