Estimation of association constants between oral malodor components and various native and derivatized cyclodextrins

The association constants of 33 oral malodorous compounds and odor precursors (9 organic acids, 7 amine-containing bases, 11 organic neutral and aromatic compounds, and 6 amino acids) with native and derivatized cyclodextrins were measured using one or more of a variety of techniques including affinity capillary electrophoresis, nuclear magnetic resonance titrations, and head-space gas chromatography. With the exception of formic acid and urea, which had binding constants that were too small to measure, all analytes showed significant binding to at least one of the cyclodextrins studied. In most cases, the native cyclodextrins exhibited the most stable complexes with these analytes. However, with cationic analytes under acidic conditions, the negatively charged sulfated and carboxymethyl cyclodextrins had higher association constants. The six amino acid precursor molecules only bound significantly with the sulfated cyclodextrins. In addition, several analyte–cyclodextrin combinations were observed to form insoluble complexes, indicating that these cyclodextrins are particularly effective at extracting these compounds from aqueous solution.