Complexation of Sulfonamides With β-Cyclodextrin Studied by Experimental and Theoretical Methods

The complex formation between three structurally related sulfonamides (sulfadiazine (SDZ), sulfamerazine (SMR), and sulfamethazine (SMT)) and β-cyclodextrin (β-CD) was studied, by exploring its structure affinity relationship. In all the cases, 1:1 stoichiometries were determined with different relative affinities found by phase solubility (SDZ:β-CD > SMR:β-CD > SMT:β-CD) and nuclear magnetic resonance (NMR) (SMT:β-CD > SMR:β-CD > SDZ:β-CD) studies. The spatial configurations determined by NMR were in agreement with those obtained by molecular modeling, showing that SDZ included its aniline ring into β-CD, while SMR and SMT included the substituted pyrimidine ring. Energetic analyses demonstrated that hydrophobicity is the main driving force to complex formation.