Cyclic peroxides and the thiobarbituric assay.

Several monocyclic peroxide compounds and two acyclic hydroperoxides have been tested for activity in the thiobarbituric acid test. All cyclic peroxides tested which have beta dioxygen functionality on non-tertiary carbons gave positive thiobarbituric acid tests at 532 nm. (epsilon = 10(3) --10(4)) Two acyclic unsaturated hydroperoxides which were derived from gamma-linolenic acid also gave positive thiobarbituric acid tests. In addition to the 532-nm-absorbing species, all peroxidic compounds tested showed a transient absorption at 450 nm during the thiobarbituric acid test. The species responsible for this 450 nm absorption appears to be an intermediate in a series reaction sequence. This intermediate is converted, in time, to the 532-nm-absorbing species. Thiobarbituric acid assay of the crude autoxidation product mixture of gamma-linolenic acid also shows this transient 450-nm-absorbing species. Added ferric ion enhances the 532 nm abosrbance of the thiobarbituric acid assay of cyclic peroxides.