Synthesis and Properties of a pH‐Insensitive Fluorescent Nitric Oxide Cheletropic Trap (FNOCT)

The synthesis and properties of the new fluorescent nitric oxide cheletropic trap (FNOCT) 14 , designed for the trapping and quantification of nitric oxide (NO) production in chemical and biological systems, is described (Scheme 3). The dicarboxylic acid 14 and the corresponding bis[(acetyloxy)methyl] ester derivative 15 of the FNOCT contain a 2‐methoxy‐substituted phenanthrene group as fluorophoric unit. The fluorescence of the reduced NO adduct of this FNOCT (λ_exc 320 nm, λ_em 380 nm) is pH‐independent. Trapping experiments were carried out in aqueous buffer solution at pH 7.4 with nitric oxide being added as a bolus as well as being released from the NO donor compound MAHMA NONOate (= (1Z)‐1‐{methyl[6‐(methylammonio)hexyl]amino}diazen‐1‐ium‐1,2‐diolate), indicating a trapping efficiency of ca. 50%. In a biological application, nitric oxide was scavenged from a culture of lipopolysaccharide‐stimulated rat alveolar macrophages. Under the applied conditions, a production of 11.1 ± 1.5 nmol of NO per hour and per 10⁵ cells was estimated.