Antioxidant effects of rosemary extracts on sunflower oil compared with synthetic antioxidants

Summary The antioxidant activities of ethanol extracts of rosemary ( Rosmarinus officinalis L.) (RE) were tested in natural sunflower oil stored at 60 °C by measuring their peroxide values ( POV ), thiobarbituric acid‐reactive substances ( TBARS ), free fatty acid ( FFA ) content and p‐anisidine value ( AnV ) after regular intervals compared with synthetic antioxidants. After 3 weeks of storage at 60 °C, sunflower oil containing 200 mg kg −1 rosemary extracts showed lower POVs (75.7 ± 0.47  meq kg −1 ), thiobarbituric acid‐reactive substances ( TBARS )(0.161 ± 0.002 μg mL −1 ), FFA contents (0.45 ± 0.04 mg g −1 ) and AnV (12.4 ± 0.02) than the control sample. Sunflower oil containing 200 ppm butylated hydroxyanisole ( BHA ), butylated hydroxytoluene ( BHT ) and tert‐butylhydroquinone ( TBHQ ) showed POVs (204 ± 0.68, 159 ± 0.55, 20 ± 0.49 meq kg −1 ), thiobarbituric acid‐reactive substances ( TBARS ) (0.171 ± 0.002, 0.184 ± 0.002, 0.069 ± 0.001 μg mL −1 ), FFA contents (0.34 ± 0.03, 0.46 ± 0.03, 0.2 ± 0.01 mg g −1 ) and AnV (14.7 ± 0.03, 16.5 ± 0.04, 6.77 ± 0.01), respectively, after 3 weeks of storage at 60 °C. These results illustrate that rosemary extracts exhibited very strong antioxidant activity, almost equal to that of synthetic antioxidants ( BHA and BHT ).