title: Spectra and structure of complexes formed by sodium fusidate and potassium helvolate with beta- and gamma-cyclodextrin.
abstract: The complexation of two steroid antibiotics of the fusidane family, sodium fusidate and potassium helvolate, by beta-CD and gamma-CD has been studied by using 1D and 2D-NMR techniques. Both guests form 1:1 complexes with gamma-CD and 1:2 (guest:cyclodextrin) complexes with beta-CD. Thus, both antibiotics behave as monotopic and ditopic guests when they are complexed by gamma-CD and beta-CD, respectively. Both steroids enter into the cavity of the gamma-CD by the side chain, reaching the central region of the steroid (rings C and D), whereas the A and B (partially) rings remain outside. For beta-CD complexes, ROESY spectra show a remarkable absence of interactions of the protons of the C and D rings, whereas clear interactions corresponding to the side chain, and A and B rings are observed. The obtained equilibrium constants (see previous paper) are discussed in terms of the structures proposed for the complexes. NMR spectra of sodium fusidate are revised, and a full assignment of the 1H and 13C NMR spectra is presented for potassium helvolate.
authors.affiliation: Facultad de Ciencias, Departamento de Química Física, Universidad de Santiago de Compostela, Campus de Lugo, Spain.
authors.forename: Aida
authors.initials: A
authors.lastname: Jover
authors.forename: Rosane M
authors.initials: RM
authors.lastname: Budal
authors.forename: Wajih
authors.initials: W
authors.lastname: Al-Soufi
authors.forename: Francisco
authors.initials: F
authors.lastname: Meijide
authors.forename: José
authors.initials: J
authors.lastname: Vázquez Tato
authors.forename: Rosendo A
authors.initials: RA
authors.lastname: Yunes
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001665:Binding Sites; D003505:Cyclodextrins / Q000737:chemistry*; D016503:Drug Delivery Systems; D005672:Fusidic Acid / Q000031:analogs & derivatives* / Q000737:chemistry*; D008956:Models, Chemical; D008962:Models, Theoretical; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D047392:beta-Cyclodextrins; D047408:gamma-Cyclodextrins
chemical_list: D000900:Anti-Bacterial Agents; D003505:Cyclodextrins; D047392:beta-Cyclodextrins; D047408:gamma-Cyclodextrins; D005672:Fusidic Acid; C031215:betadex; C023792:gamma-cyclodextrin; C011267:helvolic acid