Superoxide (O2 •-) and peroxynitrite (ONOO-) have been implicated in many pathophysiological conditions. To develop novel catalysts that have both ONOO- decomposition and O2 •- dismutase activity, and to understand the mechanisms of these processes, we have explored the reactivity of 5,10,15,20-tetrakis(N-methyl-4‘-pyridyl)porphinatomanganese(III) [Mn(III)TMPyP] toward ONOO- and O2 •-. The reaction of Mn(III)TMPyP with ONOO- to generate an oxomanganese(IV) porphyrin species [(oxoMn(IV)] is fast, but Mn(III)TMPyP is not catalytic for ONOO- decomposition because of the slow reduction of oxoMn(IV) back to the Mn(III) oxidation state. However, biological antioxidants such as ascorbate, glutathione, and Trolox rapidly turn over the catalytic cycle by reducing oxoMn(IV). Thus, Mn(III)TMPyP becomes an efficient peroxynitrite reductase when coupled with ascorbate, glutathione, and Trolox (k c ≈ 2 × 106 M-1 s-1), though the direct reactions of ONOO- with these biological antioxidants are slow (88 M-1 s-1, 5.8 × 102 M-1 s-1, and 33 M-1 s-1, respectively). Mn(III)TMPyP is known to catalyze the dismutation of O2 •-, and using stopped-flow spectrophotometry, the rate of Mn(III)TMPyP-catalyzed dismutation has been measured directly (k c = 1.1 × 107 M-1 s-1). Further, O2 •-, like the biological antioxidants, rapidly reduces oxoMn(IV) to the Mn(III) oxidation state (k ≈ 108 M-1 s-1), transforming Mn(III)TMPyP into a O2 •--coupled ONOO- reductase. Under conditions of oxidative stress and reduced antioxidant levels, Mn(III)TMPyP may deplete O2 •- primarily as a function of its ONOO- reductase activity, and not through its O2 •- dismutase activity.

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For these amphiphilic analogs of FeTMPyP and MnTMPyP, the polarity of the environment of the metalloporphyrin headgroup is intimately related to the efficiency of the catalyst; a polar aqueous environment is essential for effective catalysis of ONOO- decomposition. Thus, catalysts 1b. and 2b. react rapidly with ONOO- and are potential therapeutic agents that, unlike their water-soluble TMPyP analogs, could be administered as liposomal formulations in SLs. These SL-bound amphiphilic metalloporphyrins may prove to be highly effective in the exploration and treatment of ONOO- related disease states.

Fused pyrimidine derivativesFused pyrimidine derivatives R 0515 p38 Inhibitors: Piperidine-and 4-Aminopiperidine-Substituted Naphthyridinones, Quinolinones, and Dihydroquinazolinones. -(HUNT*, J. A.; et al.; Bioorg.

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