Nitrosation and nitrosylation of haemoproteins and related compounds. Part 1. Porphyrins and metalloporphyrins

Abstract

Acidified nitrite mixtures react with octaethylporphyrin, mesoporphyrin dimethyl ester, and (less effectively) octaethylhaemin to give meso-nitro-derivatives. Such products are also furnished by the reaction of sodium nitrite or nitric oxide with a preparation of the radical cation of zinc(II) octaethylporphyrin. The radical cation also gives meso-substituted derivatives with chloride, thiocyanate, and benzoate ions.

Nitrosylhaems are characterised from the reactions of nitric oxide with octaethylhaemin and protohaemin dimethyl ester. The pigment of cured meat, nitrosylprotohaem, has been fully characterised (as its dimethyl ester) for the first time. The reaction of excess of acidified nitrite with octaethylhaemin for a short period gives a product regarded as a mixture of mono- and di-nitrosyl derivatives, but in the presence of ascorbic acid nitrosylocataethylhaem is formed cleanly. Under suitable conditions nitrosylhaems react with secondary amines to generate nitrosamines. The results are discussed in the context of the chemistry of meat curing processes.