Hydrogen-donating mechanism of rosmariquinone, an antioxidant found in rosemary

Rosmariquinone (RQ), an ortho-quinone diterpenoid found in rosemary, was shown to act as a hydrogen-donating antioxidant. The proposed mechanism is based on the isolation of the catechol intermediate arucadiol (AD) in methyl oleate test systems. AD was also observed in a bulk soybean oil oxidation experiment, which supports the observation that RQ is converted to AD during oxidation of the oil. Because AD was found in both light-induced oxidation and autoxidation test systems, the antioxidant mechanism proceeds in a similar manner. The antioxidant activities of RQ and AD were not significantly different in the autoxidation experiments, while AD was a significantly better (P < 0.05) antioxidant than RQ in the light-induced oxidation.