Nitrite contamination in hypotensive preparations of dinitrosyl iron complexes with glutathione

Summary The content of nitrite admixture in preparations of dinitrosyl iron complexes (DNIC) with glutathione synthesized by treatment of aqueous solutions of Fe 2+ + glutathione with gaseous NO (complex 1) or by mixing solutions of S-nitrosoglutathione (GS-NO) with solutions of Fe 2+ + glutathione (complex 2) was determined using the Griess method and HPLC as well as from the level of HNO 2 formed upon interaction of gaseous NO with acidified distilled water. In both preparations, DNIC were predominantly represented by the binuclear form (B-DNIC). In complex 1, the appearance of nitrite in DNIC solutions was induced by nitrogen dioxide present in gaseous NO; its interaction with NO gives an adduct, which is further hydrolyzed to nitrite in aqueous solutions. In complex 2, the presence of nitrite admixture could appear in the presence of nitrite non-incorporated into GS-NO synthesized by mixing glutathione and nitrite in acid media. The per cent content of nitrite (with respect to the total content of complex 1) was 6%, whereas in complex 2 it was as low as 0.4%. Such a low level of nitrite contamination in the course of conventional synthesis of DNIC with glutathione does not make any significant contribution to their biomedical (e.g., hypotensive or vasodilator) activity.