Two novel salicylate-derived quinhydrones were evaluated for their effect on the kinetics of cyclooxygenase activity of sheep seminal vesicle prostaglandin H synthase. These quinhydrones, which form semiquinone radicals in solution, were designed to resemble oxidized intermediates of salicylic acid metabolism. Although initially investigated for their potential role in irreversible inactivation of cyclooxygenase, these derivatives were found to give three-fold stimulation of this activity. In the absence of arachidonic acid, preincubation of the enzyme with these quinhydrones did not lead to inactivation of the cyclooxygenase activity. These compounds thus resemble the phenolic antioxidants in their effects on the cyclooxygenase activity of the synthase.
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