The antioxidant activities of the essential oil and crude methanolic extract (CEx) of cumin seed (Cuminum cyminum) were evaluated. Total phenolics and tocopherols contents, reducing power, DPPH radical-scavenging capacity (EC50), and the oxidative/oil stability index were assessed. The contents of total phenolics and total tocopherols in the essential oil (18.47 and 0.11 mg/g, respectively) were significantly lower than those of the CEx (29.12 and 0.42 mg/g, respectively). The CEx had an EC50 value (0.74 mg/mL) significantly lower than those of the essential oil and a-tocopherol (1.20 and 32.50 mg/mL, respectively). The reducing power of the CEx (459.46 mmol Fe2þ per mass) was significantly higher than those of the essential oil (18.47 mmol/L) and a-tocopherol (99.96 mmol/L). The addition of CEx to the purified sunflower oil significantly improved its oxidative stability at the levels of 800 ppm and higher whereas the essential oil indicated no antioxidant activity at the levels experimented (200–2000 ppm). The CEx was considered to be a useful antioxidative compound in bulk oil and emulsion systems but the essential oil showed no antioxidant activities. The CEx in the bulk oil system had higher antioxidant activities than in the emulsion system. The CEx concentration of 2000 ppm showed the highest antioxidant activity and reduced the formation of hydroperoxides and secondary products more than the other antioxidative compounds applied in this study.

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