Background: Probiotics are survival microorganisms that, when administered in sufficient amounts, confer health benefits to the host and can be used in an antioxidative role. Objectives: The antioxidative effect of whole cells and intracellular cell-free extracts of the lactic acid bacteria Lactobacillus acidophilus (PTCC 1643) as a probiotic at three different time intervals was investigated. Materials and Methods: Antioxidant biomarkers, such as total antioxidant power (TAP), measured with the FRAP (ferric-reducing ability of plasma) method, were evaluated at 24, 48, and 72 hours. Results:The results showed that extracts and bacteria of L. acidophilus were able to significantly increase TAP after 24 and 72 hours. Conclusions:The results showed that the effect of L. acidophilus is time-dependent.