AbstractBackground: Antioxidants are known to play a role in the prevention of coronary artery disease (CAD) whereas oxidative stress contributes to endothelial dysfunction and the development of atherosclerosis. Studies have reported low levels of total antioxidant capacity (TAC) in ACS patients. The objective of our study was to evaluate levels of TAC between different populations and its prognostic value. Methods and Results: A total of 163 subjects were included in the study consisting of Control (N=21), Chronic Stable Angina (CSA) (N=21), Non-ST-elevation myocardial infarction (NSTEMI) (N=57) and ST-Elevation Myocardial Infarction (STEMI) (N=64) patients between the period March 2017 to April 2018. Antioxidant levels from the plasma samples were measured by Trolox Equivalent Antioxidant Capacity (TEAC) assay. Patients were also followed up at different time intervals to identify the occurrence of major adverse cardiac events (MACE). All statistical analyses were performed using SPSS software version 16.0 (SPSS Inc., Chicago, IL). The concentration between the 3 groups varied significantly (p=0.002) with an average trolox concentration of 1.562 mM as observed in Control, 2.05 mM in CSA and 2.55 mM in ACS subjects. We also observed a negative correlation between TAC and cardiac markers, creatine phosphokinase (CPK) (r= -0.194, p=0.040) and Creatine kinase-MB (CK-MB) (r= -0.232, p=0.013). However, TAC levels did not provide any prognostic information [AUC = 0.458, p = 0.630, 95% CI (0.297-0.619)]. Conclusion: TAC levels did not provide any prognostic value. Larger sample sizes are required to assess their role.