Neopterin as an endogenous antioxidant

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Abstract
The in vitro potency of neopterin (NP) as an antioxidant and its in vivo activity to suppress alloxan‐induced diabetes were investigated. The reduced form of neopterin, 5,6,7,8‐tetrahydroneopterin (NPH‐4), showed an extremely high superoxide anion radical scavenging activity in two assay systems, i.e. xanthine/xanthine oxidase‐ and macrophage/phorbol myrislate acetate (PMA)‐reaction systems. NPH‐4 also inhibited the oxidation of linoleic acid about as effectively as uric acid. Furthermore, NPH‐4 and NP effectively suppressed alloxan‐induced mouse diabetes. These results suggest that pteridines play an important role as endogenous antioxidant.