A symbol of longevity and vitality in Ancient China, the leaves, seeds, fruits and nuts of ginkgo biloba were used by traditional healers to treat a wide variety of human ailments. These included lung diseases like tuberculosis, asthma and bronchitis, leukorrhea (abnormal vaginal discharge), diarrhea and skin diseases.
Modern researchers, however, have discovered other medicinal uses for this ancient plant. In a recent study, South Korean researchers investigated the neuroprotective properties of ginkgo biloba, which have been consistently reported by a number of studies. They specifically focused on the effects of ginkgo biloba extract (GBE) on hypoxic injury to retinal ganglion cells (RGC), which are nerve cells found near the surface of the retina, both in vitro and in vivo.
The researchers reported their findings in an article published in the Journal of Medicinal Food.
Ginkgo biloba can protect retinal neurons from degeneration that leads to glaucoma
Oxidative stress induced by inadequate oxygen supply (hypoxia) and disturbed microvascular circulation is both implicated in the pathogenesis of glaucoma. Glaucoma is the medical term for a group of eye conditions that damage the optic nerve. Located in the back of the eye, the optic nerve is responsible for transferring visual information in the form of electrical impulses to the vision centers of the brain.
Abnormally high fluid pressure inside the eye is the number one cause of optic nerve damage. When this pressure -- also called intraocular pressure -- becomes too high, it compresses the optic nerve, causing nerve cells to die. This gradual loss of nerve cells causes blind spots to develop in a person’s visual field -- a definite sign of glaucoma. Although most common in older adults, glaucoma can occur at any age and is the leading cause of blindness in people over the age of 60.
According to previous studies, GBE has shown neuroprotective activities against oxidative stress and impaired vascular circulation. Oxidative stress is the result of an imbalance between antioxidant and free radical production; it is said to occur in glaucoma and contributes to the loss of RGC, one of the five types of neurons present in the retina.
For their in vitro experiment, the researchers first induced oxidative stress in RGC using hydrogen peroxide (H2O2). They then treated the cells with a vehicle (control) or EGb 761, a standardized GBE. (Related: From reduced glaucoma risk to better skin, here are 8 reasons to eat collard greens.)
Meanwhile, for their in vivo experiment, the researchers induced hypoxic optic nerve injury by clamping the optic nerve of rats with a microserrefine clip, which was applied without crushing the optic nerve. They then administered different concentrations of EGb 761 or the vehicle to the animals intraperitoneally and measured RGC density to estimate cell survival both in vitro and in vivo.
The researchers reported that compared with the vehicle-treated RGC, ganglion cells treated with 1 or 5 mcg/mL EGb 761 had a significantly higher survival rate. In vivo, RGC density upon treatment with either 100 mg/kg body weight or 250 mg/kg body weight EGb 761 was also significantly higher than the density measured after treatment with the vehicle.
Based on these findings, the researchers concluded that ginkgo biloba extract has neuroprotective effects against hypoxic injury that causes glaucoma.
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