Loss of α‐tocopherol upon exposure to nitric oxide or the sydnonimine SIN‐1

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Abstract
SIN-1 which spontaneously decomposes to yield nitric oxide (NO. and Superoxide anion (O2 .− radicals caused a loss of microsomal α-tocopherol paralleled by the formation of α-tocopheryl quinone. The loss was partially prevented by Superoxide dismutase but not by catalase. The SIN-1-induced loss of α-tocopherol also occurred when tocopherol was dissolved in ethanol/potassium phosphate buffer (20/80, v/v). Likewise, addition of authentic NO. to α-tocopherol dissolved in ethanol resulted in loss of the vitamin and quinone formation. These results suggest that NO. or its products such as peroxynitrite or nitrogen dioxide react with α-tocopherol, the quinone derivative being a major oxidation product. Depletion of vitamin E by NO. may contribute to tissue injury, e.g. in neuronal tissues.