Quinone-enhanced Ascorbate Reduction of Nitric Oxide: Role of Quinone Redox Potential

Abstract

The quinones 1,4-naphthoquinone (NQ), methyl-1,4-naphthoquinone (MNQ), trimethyl-1,4-benzoquinone (TMQ) and 2,3-dimethoxy-5-methyl-1,4-benzoquinone (UQ-0) enhance the rate of nitric oxide (NO) reduction by ascorbate in nitrogen-saturated phosphate buffer (pH 7.4). The observed rate constants for this reaction were determined to be 16±2,215±6,290±14 and 462±18 M^-1 s^-1, for MNQ, TMQ, NQ and UQ-0, respectively. These rate constants increase with an increase in quinone one-electron redox potential at neutral pH, E₇₁. Since NO production is enhanced under hypoxia and under certain pathological conditions, the observations obtained in this work are very relevant to such conditions.

• Quinones, 1,4-naphthoquinone
• Nitric oxide
• Methyl-1,4-naphthoquinone
• Trimethyl-1,4-benzoquinone
• 2,3-dimethoxy-5-methal-1,4-benzoquinone