The present study was designed to evaluate the safety degree of lactic acid bacterial (LAB) usage on mammalian cells and anti-oxidative ability of their intact cells, and both extra-and intra-cellular extracts. The non-toxic doses of eleven different LAB strains were detected by cytotoxicity assay test on peripheral blood mononuclear cells (PBMC) using neutral red stain. The antioxidant properties of LAB strains were evaluated biochemically using OH- scavenging assay, superoxide scavenging assay, hydrogen peroxide scavenging assay, DPPH radical scavenging assay, reducing ability assay, inhibition of lipid peroxidation assay, and inhibition of human blood erythrocyte haemolysis assay. In addition, in-vitro antioxidant evaluation was carried out by using Flow Cytometric assay, on which the ROS produced by the stress factor Helicobacter pylori LPS on PBMC. The cytotoxicity results clarified that the safe doses of LAB extracellular extracts reached up to 20% while, the intracellular extracts safe doses reached up to 14%. Out of eleven tested LAB strains, Lactobacillus plantarum, Lactobacillus bulgaricus DSMZ 20080 andLactobacillus acidophilus showed maximum free radical scavenging abilities at two levels: at intact cell level and at extract levels. In addition, in-vitro assay showed that ROS scavenging ability reached up to 100% in case of using mixture of both extracts of these strains.
Key words: Lactic acid bacteria, antioxidant, DPPH, flow cytometer
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