Ikeda Mohando Ltd.

Guanosine 7-N-oxide (I) [106073-74-9] was prepared from guanine 7-N-oxide  [5227-68-9] and ribose 1-phosphate  [14075-00-4] using a cell suspension of Bacillus subtilis.The reaction is catalyzed by bacterial purine nucleoside phosphorylase.After incubation at 60° for 3.5 h, the reaction mixture is centrifuged and the supernatant was applied onto Dowex 50W × 4 and eluted with 0.2M NH₄HCO₃.The fractions containing I were concentrated in vacuo and purified by gel filtration on Sephadex G-10.The physicochem. properties of I are given.I had a very weak antimicrobial activity but it inhibited L-5178Y mouse leukemia cells in culture at IC₅₀ of 0.60 μg/mL (2.01 × 10^-6M).I.p. administration of I showed a life prolongation effect on mice bearing P388 leukemia.It also showed a dose-dependent inhibition of the growth of Ehrlich solid carcinoma in mice.Mouse tolerated I at 50 mg/kg, i.p.