Protection against tBHP-induced oxidative stress by SFE. Cell viability was quantified by a Calcein AM assay 24 h after exposure to t-BHP, following a 2 h pretreatment with SFE. Treatment with t-BHP (50 μM) alone was seen to significantly decrease cell viability. SFE showed protection against t-BHP-induced cell toxicity in a dose-dependent manner. Values represent mean ± SD (n=5).