Reaction of reduced metronidazole with guanosine to form an unstable adduct.

Metronidazole, which is known to react with DNA under certain conditions, forms an adduct with guanosine in the presence of the reducing agent, sodium dithionite. This product has been purified by HPLC, characterized by UV and fast atom bombardment mass spectrometry, and tentatively identified as 1-(2-hydroxyethyl)-2-methyl-5-(N2-guanosinylamino)imidazole. This adduct is very unstable and decomposes to a variety of products including guanosine. Formation of this and similar DNA adducts from metronidazole in vivo, and the decomposition of these products, are probably both strongly dependent on details of intracellular metabolism.