Antioxidative Effect of Lactic Acid Bacteria: Intact Cells vs. Intracellular Extracts

Abstract

The present study compared the anti-oxidative ability of intact cells and intracellular extracts of two lactic acid bacterial strains, Bifidobacterium longum and Lactobacillus delbrueckii ssp. bulgaricus. Results showed that both intact cells and intracellular extracts of 10(9) cells of B. longum and L. delbrueckii ssp. bulgaricus had the ability to scavenge alpha-diphenyl-beta-picrylhydrazyl (DPPH) free radical by 70.4-75.1%, to inhibit liposome peroxidation by 25-31%, and to decrease significantly the malondialdehyde (MDA) production in Intestine 407 cells. The effect of intact cells and intracellular extracts of these two bacterial strains on the oxidation of low density lipoprotein (LDL) isolated from cerebrovascular accident (CVA) patients and healthy subjects was also compared. Oxidation of LDL was monitored by measuring the lag time for the formation of conjugated dienes in isolated LDL particles. When LDL was treated respectively with 10(9) intact cells of B. longum and L. delbrueckii ssp. bulgaricus, the lag time of oxidation of LDL was prolonged significantly. The extent of inhibition was greater on LDL isolated from healthy subjects than from CVA patients. When LDL from either CVA patients or healthy subjects was treated with intracellular extracts of 10(9) cells of B. longum and L. delbrueckii ssp. bulgaricus, respectively, the copper-mediated oxidation was extensively inhibited with a lag time exceeding 180 min. Results from this study show a greater inhibitory effect on LDL oxidation exerted by the intracellular extract than the intact cells, suggesting the presence of effective inhibitory factors in the intracellular extract.