Spectroscopic investigation of the conformational properties and self-association behaviour of natural compounds in solution

The conformational properties and self-association behaviour of rifaximin and rifaximin OR (Open Ring) were investigated in solution by NMR and IR spectroscopy. The dependence of proton chemical shift on concentration and temperature were analysed to study the self-association process. IR spectra of rifaximin and rifaximin OR were also used at different concentrations to investigate the entity of specific inter- and intra:molecular interactions. Although similar in structure the two molecules had different chemical properties in solution. This could be of some interest in view of the biological importance of this class of antibiotic molecules.