ABSTRACT
Dept. of Neurological, Neurosurgical and Behavioural Sciences, “Giorgio Segre” Pharmacology Section, University of Siena.
The extract of Ginkgo biloba L. (Egb 761) is known for its therapeutic properties andhas been used to increase peripheral and cerebral blood flow as well as for the treatment of dementia.
EGb761 is a standard extract from the leaves of Ginkgo biloba containing 24% ginkgo-flavone glycosides and 6% terpenoid (e.g. ginkgolides A, B, C, J and bilobalide) (1).
The numerous pharmacological activities allow to use it in many pathological conditions (metabolic, hemodynamic, hemorheological) occurring in cerebral, retinal, cochleo-vestibular, cardiac or peripheral ischemia. Additionally, EGb761 inhibits the PAF (platelet activating factor), is a potent free radical scavenger (2), and in ischemic retina animal models, EGb improved retinal functioning by decreasing oxidative retinal stress (3).
The aim of this study was to assess the effect of Egb 761 (100 mg/kg) on non-enzymatic retinal antioxidant defense system: glutathione reduced (GSH) and glutathione oxidized (GSSG), ascorbic acid (AA) in a rat model of retinal damage induced by ischemia.
Male albino Wistar rats were divided into 3 groups: (I) control group without treatment, (II) group subjected to retinal ischemia and (III) group subjected to retinal ischemia and then treated with Egb 761 (100 mg/kg/day orally) for 7 days. After 7 days the animals were sacrificed and the retina were rapidly removed and utilizedto determination of biochemical parameters involved in antioxidant defense system. In addition we have determinedmalondialdehyde (MDA) levels as index of lipid peroxidation and cellular damage.These parameters were measured by spectrophotometric and HPLC methods.
Data obtained showed a decrease significantly (P<0.02) of GSH levels (-25%), AA (-18%) and an increase of MDA (+10%) after ischemia (group II) respect to group I. After Egb 761 administration in the group III GSH and AA increase significantly (+15%, P<0.02 and +11%, P<0.05 respectively) respect to group II but however remained significantly lower respect to control group (10% and -6%, P<0.05 respectively). In addition the MDA levels remained unchanged respect to ischemic group and increased (+8% P<0.05) respect to controls.
The results suggest that Egb 761 may to protect the retina by oxidative damage and it may be used as agent for improving the antioxidant defensive system, even if it doesn't appear to be sufficient to counteract completely the ischemic damage.
References
- De Feudis FV: Ginkgo biloba extract (EGb761): pharmacological activities and clinical applications. Elsevier, Paris, 1991.
- McKenna DJ, Jones k, Hughes K. Efficacy, safety, and use of Ginkgo biloba in clinical and preclinical applications. Altern Ther Health Med.2001;7:70-90.
- Droy-Lefaix MT, Cluzel J, Menerath JM, Bonhomme B, Doly M. Antioxidant effect of a Ginkgo biloba extract (EGb 761) on the retina. Int J Tissue React.1995;17:93-100.