Edible wild vegetable, Gymnaster koraiensis protects retinal ganglion cells against oxidative stress

This study was conducted to determine whether Gymnaster koraiensis is effective at blunting the negative influence of N-methyl-d-aspartate (NMDA) on the retinas of rats and on oxidative stress induced cell death in transformed retinal ganglion cells (RGC-5).The ethyl acetate fraction of G. koraiensis (EAGK) and the isolated compound, 3,5-di-O-caffeoylquinic acid (3,5-DCQA), were shown to significantly attenuate the negative effect of H₂O₂ on the RGC-5 cells tested by various procedures.The inclusion of EAGK or 3,5-DCQA in the culture reduced the reactive oxygen species (ROS) and replenished the reduced glutathione levels caused by various radical species such as H₂O_2, O₂⁻ or OH. Moreover, EAGK or 3,5-DCQA inhibited lipid peroxidation caused by sodium nitroprusside (SNP) in rat brain homogenates.From in vivo experiments, the presence of NMDA in the retina affected the thickness of the inner plexiform layer (IPL) and the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) in positive ganglion cells. EAGK or 3,5-DCQA protected the thinning of the IPL and increased TUNEL positive cells in the ganglion cell layer (GCL).Our results clearly demonstrate the neuroprotective effect of EAGK both in vitro and in vivo. Moreover, 3,5-DCQA is suggested to be the active compound of EAGK.