Dual Effects of Plant Antioxidants on Neuron Cell Viability

  Background : Many studies have focused on oxidative stress induced damage and hence, the protective effects conferred by antioxidants. An example is neurodegenerative diseases which is thought to occur due to neuronal loss associated with oxidative stress. However, some antioxidants such as vitamin E have been shown to also exert pro-oxidative effects at high concentration.   Objective : In this study the cytotoxicity and neuroprotective potentials of Chlorella vulgaris (CV), Momordica charantia (MC) and Piper betle (PB) were investigated and correlated with the antioxidant potential. Tocotrienol Rich Fraction (TRF) served as positive control since it had been shown previously to have high antioxidant potential as well as to exert neuroprotective and neurocytotoxic effects.   Method : Free radical scavenging activities of hot water extract of CV, aqueous extract of MC, aqueous extract of PB and TRF were determined by using DPPH (1, 1-diphenyl-2-picryl-hydrazyl) assay. Cytotoxicity and neuroprotective effects were measured by using 3 - (4, 5 -dimethylthiazol-2-yl) -5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium salt (MTS) against BSO-induced neuron cell death.   Results : Results showed that TRF has the highest radical scavenging activity followed PB> MC> CV. The MTS results showed that TRF (1-50 µg/ml) as positive control, PB (0.001-100µg/ml) and MC (1-500µg/ml) conferred significant protection against BSO-induced cell death. These plants were cytotoxic at high concentrations. However CV extract did not show significant neuroprotective effect against BSO-induced cell death nor cytotoxic effect. Conclusion : The present findings showed that plant extracts with the higher free radical scavenging activity showed neuroprotective effects at low concentrations but were cytotoxic at higher concentrations.