Antioxidant effect of a Ginkgo biloba extract (EGb 761) on the retina

Several investigations have recently shown that the retina is very sensitive to oxygenated free radicals (O2-, OH.) at the origin of the membrane phospholipids peroxidation. Peroxy radical (ROO.) release is responsible for the induction of electrophysiological disturbances leading to retinopathy development. As Ginkgo biloba extract (EGb 761, IPSEN, France) was reported to scavenge primary (O2-, OH.) and secondary (ROO.) free radicals, we evaluated its antioxidant effect on retinas of albino rats submitted to different types of aggressors. On isolated rat retina, EGb 761 given orally significantly protected against lipoperoxidation induced by a mixture of ferrous sulfate and sodium ascorbate added to the perfusion solution. With EGb 761, the decrease of the b-wave ERG amplitude was less pronounced and the retina survival was increased. EGb 761 was also effective against ischaemia-reperfusion disorders due to occlusion of the central retinal artery or by intraocular hypertony. Like other antioxidants such as superoxide dismutase tested on these models, EGb 761 significantly attenuated, according to a dose-response effect, the free-radical injury. EGb 761 reduces the decrease of the b-wave amplitude, the oedema, necrosis and ion homeostasis disturbances. Xenobiotics are also responsible for the retinotoxicity partly due to free radicals and PAF release. We noted an EGb 761 dose-dependent protective effect against acute and chronic chloroquine toxicity to the retina. The deleterious effect of chloroquine was characterized by a delayed b-wave and an asymmetry of the signal with slow declining b-wave. After EGb 761 treatment, the ERG aspect was partially normal. In conclusion, EGb 761, by its general free-radical scavenger properties, is an antioxidant that inhibits or reduces the functional and morphological retina impairments observed after lipoperoxide release.