A sweeter way to combat Helicobacter pylori? Bismuth(III) complexes and oxido-clusters derived from non-nutritive sweeteners and their activity against H. pylori

Eight new homo-and hetero-leptic bismuth(III) complexes and two new polynuclear bismuth(III) oxido clusters derived from acetosulfame (AceH) and cyclamic acid (CycH(2)) have been synthesised and characterised. Complexes, [Ph2Bi(Ace)] 1, [Bi(Ace)(3)] 2, [PhBi(Ace)(2)] 3, [Bi(CycH)(3)] 6, [Ph2Bi(CycH)] 7 and [PhBi(CycH)(2)] 8 were synthesised by treating BiPh3 with the appropriate acid in 1: 1, 1: 2 and 1: 3 stoichiometric ratios under solvent-free or solvent-mediated conditions. Complex 4, [Bi(OH)(Ace)(2)], was obtained from the hydrolysis of 3. [Bi-2(Cyc)(3)] 9 was obtained from the reaction of cyclamic acid with (Bi(OtBu)(3)) in a 3: 2 ratio under inert conditions. The polynuclear bismuth oxido clusters, [Bi50O64(Ace)(22)(H2O)(10)] 5 and [Bi38O45(CycH)(24)(H2O)(14)] 10 were obtained using Bi2O3 under sonication in water and their composition confirmed through elemental and thermogravimetric analyses. The DMSO soluble complexes, 1, 2, 4, 5, 6, 7 and 9, were all assessed for their in-vitro activity against three strains of H. pylori (251, 26695 and B128). All compounds gave an MIC value of 6.25 mu g/mL, indicating that bactericidal activity is insensitive to increased substitution by acetosulfamate or cyclamate at the Bi(III) centre. (C) 2012 Elsevier B. V. All rights reserved.