Characteristics of the excited states of Nitrofurantoin, an anti-inflammatory and photoactive nitrofuran derivative

Abstract Spectral characteristics of bio and photoactive nitrofuran derivative drug [ N -(5-nitro-2-furfurylidene)−1-aminohydantoin], (Nitrofurantoin, NFT) were investigated using optical absorption and fluorescence spectroscopies, both in “steady-state” and time resolved forms. The irradiation of the NFT in the UV region in aqueous solution induces the fluorescence with quantum yield Φ fl ≈0.03% and lifetime τ fl ≈1 ns with these values being practically independent of the NFT protonation state. The NFT transient absorption spectrum and lifetime (τ T ) depend on the NFT protonation state with τ T being 0.04 μs for mono-protonated NFT state, 0.22 μs for its non-protonated one, and with quantum yield, Φ T ≈ 0.0001% which is practically independent of its protonation state. The quenching of this transient by molecular oxygen accompanied by simultaneous singlet oxygen formation ( 1 O 2 ) allows associate this specie with the NFT molecules in the triplet state being the efficiency of this process dependent of NFT protonation state, η pH10 ≈0.53 and η pH2.5 ≈0.07. The extremely low quantum yields, Φ fl and Φ T , and short τ fl and τ T are, probably, associated with alternative ways of the dissipation of the NFT excited state energy: the NFT photoisomerization and NO • photorelease. The synergic action of two highly reactive species such as 1 O 2 and NO • in biological medium is extremely valuable for applications in photochemotherapy, thus making NFT a potential candidate for further studies in vitro and in vivo .