Mixture of American ginseng extract, ginkgo biloba extract and St. John's wort extract enhances the survival of axotomized retinal ganglion cells

Abstract

American ginseng (AG) saponins and Ginkgo biloba (GB) extract were shown to exhibit neuroprotective effect against ischemic injury. St. John’s wort (SJW) extract has also been shown recently to have free radical scavenging ability. GB, AG and SJW could therefore offer neuroprotection in a model of optic nerve (ON) transection, where recent evidence implicates the involvement of free radicals in the delayed death of axotomized retinal ganglion cells (RGCs). Transection of the ON 1.5mm from the optic disc was performed on adult hamsters. Starting on the day of operation, the animals received daily oral administration for 7 days of: (1) vehicle (0.01M PBS), (2) GB extract (2, 6 or 12 mg), (3) AG extract (10, 20 or 30mg), (4) SJW extract (10, 20 or 30mg), (5) 30mg of AD-FX, a mixture consisted of 80% AG and 20% GB extracts by weight or (6) 30mg of Menta-FX, a mixture composed of 30.8% AG, 7.7% GB and 61.5% SJW extracts by weight. AD-FX and Menta-FX were purchased from CV Technologies, Canada. RGCs survival 7 days post axotomy was quantified by applying 6% FluoroGold to the transected ON to retrogradely label the surviving RGCs 2 days before the animals were killed. The retinae were dissected and the number of fluorescent labeled RGCs was counted. We found that only treatment with Menta-FX can significantly augment the number of surviving RGCs 7 days after axotomy (p<0.01, one way ANOVA). We therefore showed for the first time that a mixture of GB, AG and SJW extracts, but not each of the extracts alone, can significantly enhance axotomized RGCs survival 7 days after ON transection. Supported by Research Grants from the University of Hong Kong