Suitability of TBA Method for the Evaluation of the Oxidative Effect of Non-water-soluble and Water-soluble Rosemary Extracts

The antioxidative effects of rosemary and grape-seed extracts spiked in human plasma were examined using the thiobarbituric acid (TBA) method. The TBA values of plasma spiked with reagents to generate reactive oxygen species, such as singlet oxygen (O-1(2)), hydroxyl radicals ((OH)-O-center dot), peroxynitrite (ONOO-), and superoxide anions (O-2(center dot-)), were measured by a flow injection analysis method with fluorescence (FL) detection. TBA values obtained by the addition of 50 mg/mL of rosemary extracts for O-1(2), (OH)-O-center dot, ONOO-, and O-2(center dot-) increased to 964 +/- 65%, 1063 +/- 61%, 758 +/- 78%, and 698 +/- 41%, respectively (n = 3, P < 0.01), whereas the values with 1 mg/mL of grape-seed extracts or tocopherol decreased (40.2 66.3%). Furthermore, the antioxidative effects of rosemary extract in rat plasma, spiked with reagents to generate (OH)-O-center dot, were examined by high-performance liquid chromatography with FL detection. No peak, other than TBA malondialdehyde, could be detected using wavelengths of 532 (lambda(ex)) and 553 nm (lambda(em)).