Cytoprotective and genoprotective effects of aqueous extracts of processed Pleurotus Sajor-caju fruiting bodies on hydrogen peroxide-induced damage of human peripheral blood mononuclear cells / Mohamad Fairus bin Abdul Kadir

Pleurotus sajor-caju authority is one of the mushroom species that is widely grown in Malaysia. The present study was undertaken to evaluate the antioxidant, cytotoxic, cytoprotective, genotoxic and genoprotective activities of crude water extracts of this mushroom. Crude aqueous extracts were prepared from the fruiting bodies that had been processed at different temperatures such as P1: blanching (95°C ± 2°C), P2: sun drying (30°C ± 2°C), P3: freeze drying (-46°C ± 3°C) and different temperatures of oven drying (P4: 45°C, P5: 50°C, P5: 55°C and P6: 60°C ± 2°C respectively). Antioxidant capacity of all the extracts was determined using ferric reducing power (FRAP) and DPPH free radical scavenging assays and the total phenolic content (TPC) was also determined. The TPC per gram of extract in descending order was P2, P4, P7, P6, P5, P3 and P1. Sun dried samples had the highest antioxidant activity compared to other processing method. The correlation analysis showed mild to moderate positive correlation between TPC, FRAP and DPPH. Cytotoxicity and cytoprotective activities were determined by assessing the viability of human peripheral blood mononuclear cells (PBMC) viability using MTT (3-(4, 4-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide) assay. None of the processed mushroom extracts were cytotoxic to the PBMCs. Hydrogen peroxide (H2O2), an oxidant; was used to induce cytotoxicity in PBMC. At a concentration of 0.3mM, H2O2 showed 25% inhibition of cell viability compared to untreated cells. At 100μg/ml, the extracts P3 and P4 exhibited the highest cell viability (10.24±0.36% and 8.20±1.06% increase respectively) compared with untreated PBMCs, while 20μg/ml of phytohaemagglutinin (PHA) only showed 6.66±0.52% increase in cell viability compared with untreated PBMCs. All the mushroom extracts exhibited mild protection against H2O2 induced toxicity. The highest protection of 10.47±0.87% and 15.37±0.99% at 80 and 100μg/ml respectively was by Abstract ii sun dried extracts, whereas at 10μg/ml vitamin C exerted 6.50±1.94% protection. Genotoxicity in PBMC was assessed using single cell gel electrophoresis (COMET assay). None of the mushroom extracts tested had genotoxic effects on the cells. The percentage of head DNA was more than 80% which was similar to control cells treated with water. The cells incubated with 0.2mM H2O2 caused 50% DNA damage. The genoprotective effect of the mushroom extracts was determined by assessing the COMET tail in PBMC, which had been incubated in the presence of H2O2 and the extracts. The P1 mushroom extract (80μg/ml) exhibited approximately 80% protection against H2O2 induced damage. The extracts P2, P3 and P4 of the fruiting bodies of P. sajor-caju showed similar degrees of protection. Thus, it can be concluded that the processing methods do affect the antioxidant level which in turn may affect the cytoprotective and genoprotective activities of P. sajor-caju against cellular or DNA damage induced by H2O2