Pharmacodynamics:

The extract of Ginkgo biloba characterized @ 24% Ginkgo flavone glycosides has been shown to inhibit platelet aggregation ²⁷, and demonstrates a "scavenging" effect on free radicals. ⁵ It also appears to inhibit histamines, and leukotriene production. ⁶ It has demonstrated the ability to inhibit the reduction of muscarinergic cholinoceptors and 2-adrenoceptors. It has the ability to alter the rheological properties of blood (see Clinical Studies).

The European Ginkgo product sold as EGb 761 has demonstrated an excitatory effect on the lateral vestibular nuclei (LVN) neurons and in-vivo and in-vitro studies shown to increase synaptosomal uptake of 5- hydroxytryptamine. ⁷

It has also been shown to prevent the ascorbic acid/Fe2+ induced decrease in synaptosomal membrane fluidity. "Preoccupation of neuronal membrane lipids induced by ascorbic acid/Fe2+ is associated with a decrease in membrane fluidity which, in turn, reduces the ability of the dopamine transporter to take up dopamine." ⁸

"The extract (Ginkgo biloba) slows down O2 consumption (respiratory burst) of stimulated cells by its inhibitory action on NADPH-oxides, the enzyme responsible for the reduction of O2 to O-2. Consequently, superoxide anion (O-.2) and hydrogen peroxide (H2O2) production is significantly decreased when the PMNs stimulation is done in the presence of the extract at concentrations of 500, 250 and 125 micrograms/ml. Moreover, the hydroxyl radical generation (OH) is very much decreased at concentrations as low as 15.6 micrograms Gbe/ml, which indicates that the extract also has free radical scavenging activity. Gbe is able at least to reduce very severely the activity of myeloperoxidase contained in neutrophils" ⁵.

Systemic Bioavailability-

Absorption rate was found to be 60% in tests with rats. ^9/10

Bioavailabity of ginkgolides A for humans has been reported at 98-100%, Ginkgolide B was 79-93% and over 70% or greater for bilobalide. ¹⁰

A study of 12 volunteers showed after single dose administration of Ginkgo biloba Extract @.90 mg to 3.36 mg "when given (ginkgo) orally, while fasting, the extents of bioavailability are high, as shown by bioavailability coefficients (FAUC) mean (+/- SD) values equal to 0.80 (+/- 0.09), 0.88 (+/- 0.21) and 0.79 (+/- 0.30) for Ginkgolide A, Ginkgolide B and Bilobalide respectively. Food intake does not change AUC quantitatively but increases Tmax. ¹¹

LD ^50___

LD ⁵⁰ was 7725-mg/kg b.d. weight after oral application in the mouse. Therefore, toxicity can be considered very low. ¹⁰

PUBLISHED STUDIES

Alzheimer''s Disease/ Dementia /Aging/Memory/Mental Capability-

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