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.