ACTION

Inhibition of PAF (platelet activating factor), Antioxidant (free-radical scavenging), Reduction of blood viscosity (causes an increase in the rate of blood flow), Neuro-protection, Stabilization of capillary permeability.

INDICATIONS

Ginkgo biloba is a plant extract used to alleviate symptoms associated with cognitive deficits, e.g., decreased memory performance, lack of concentration, decreased alertness, tinnitus, and dizziness. A treatment period of 4 to 6 weeks is needed before a pronounced effect could be expected (Soholm, B. 1998).

• PAF antagonist: PAF, a plasmalogen is a major mediator of hypersensitivity, acute inflammatory reactions and anaphylactic shock.
  
  Platelet activating factor (PAF)

  In hypersensitive individuals, cells of the polymorphonuclear (PMN) leukocyte family (basophils, neutrophils and eosinophils) macrophages, and monocytes are coated with IgE molecules that are specific for a particular antigen (e.g., pollen, dust, insect stings, certain molecules in foods). Subsequent re-exposure to the antigen and formation of antigen-IgE complexes provokes the synthesis and release of PAF. PAF is not stored in the body but only synthesized and released when PMNs are stimulated.

  When PAF is released, they cause; platelet aggregation, edema, PMN cell chemotaxis, contraction of smooth muscle, reduction of coronary circulation, hypertension, bronchoconstriction, increase permeability of cutaneous vessels, raised haematocrit, and secretion of lysosomal enzymes.

  Ginkgolide B blocks the binding of PAF to membrane receptors (Simon, M.F. et al., 1987) .

  

  GINKGOLIDE	R1	R2	R3	R4
  Ginkgolide A	H	HO	H	HO
  Ginkgolide B	H	HO	HO	HO
  Ginkgolide C	HO	HO	HO	HO
  Ginkgolide J	HO	HO	H	HO
  Ginkgolide M	HO	H	HO	HO

• Free radical scavenging: Ginkgo extract stimulates prostaglandin synthesis and inhibits lipid peroxidation in the cell membrane (Pincemail and Deby, 1991). Pincemail et al. (1987,1989) were also able to show that ginkgo possesses superoxide dismutase activity. Superoxide dismutase (SOD) is a group of metalloenzymes that catalyze a disproportionation reaction in which superoxide is reduced to hydrogen peroxide according to the following equation:
  O₂^- + O₂^- + 2H⁺ -> H₂O₂ + O₂

• Rate of blood flow: The flow of blood is mainly influenced by the haematocrit, plasma viscosity, the aggregation and flexibility of the erythrocytes. In therapeutic concentrations of 35 to 70µg/10ml, ginkgo extract produced a significant reduction in erythrocyte aggregation in patients with vascular disease involving abnormal erythrocyte aggregation and flexibility (Ernst and Matrai, 1986) .

KEY CONSTITUENTS

Terpenoids (bilobalide), Diterpenoids (ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide J, ginkgolide M), Flavonoids: Flavones(luteolin, tricetin, 2-hydroxyluteolin), Biflavones (amentoflavone, ginkgetin, isoginkgetin, sciadoptysin, 5-methoxybilobetin, bilobetin), Flavonols (caempherol, quercetin, isorhammetin), Flavone glycosides, Flavone acyl glycosides, Catechins, Steroids (sitosterol, sitosterol glucoside).

REFERENCES

Ernst, E. and Matrai, A. (1986). Hamorheologische in-vitro Effekte von Ginkgo biloba. Herz/Kreislauf. 18;358.

Pincemail, J., Thirion, A., Dupuis, M., Braquet, P., Drieu, K., and Delby, C. (1987). Ginkgo biloba Extract Inhibits Oxygen Species Production Generated by Phorbol Myristate Acetate Stimulated Human Leukocytes. Experientia. 43(2); 181-184.

Pincemail, J., Dupuis, M., Nasr, C., Hans, P., Haag-Berrurier, M., Anton, R. and Delby, C. (1989). Superoxide Anion Scavenging Effect and Superoxide Dismutase Activity of Ginkgo biloba Extract. Experientia. 45(8); 708-712.

Pincemail, J. and Deby, C. (1991). In: F.H. Kemper and H. Schmid-Schonbein, eds. Ginkgo biloba EGb 761, Vol.1; Pharmakologie, pp.91-102. Springer Verlag, Berlin.

Simon, M.F., Chap, H., Braquet, P. and Douste-Blazy, L. (1987). Effect of BN 52021, a specific Antagonist of Platelet Factor (PAF-acether), on Calcium Movements and Phosphatidic Acid Production Induced by PAF-acether in Human Platelets. Thromb. Res. 45(4);299-309.

Soholm, B. (1998). Clinical improvement of memory and other cognitive functions by Ginkgo biloba: review of relevant literature. Adv. Ther. 15(1):54-65.

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.