Nabumetone (NAB) forms a 1/1 supramolecular complex with β- cyclodextrin (β-CD) both in the absence and presence of linear alcohols (ROH). The apparent association constants, K_(app), were measured using a steady-state fluorescence method. K_(app) decreases linearly with an increasing number of carbon atoms in the chain of the alcohol. We attribute this to a competition between nabumetone and linear alcohol for the β-CD hydrophobic cavity as detailed analysis of K_(app) as a function of [alcohol] suggests that the interactions in the β-CD/NAB/ROH system do not result in the formation of ternary supramolecular complex. Quenching the florescence of nabumetone with NaI shows that the β-CD cavity acts as a shield against contact between nabumetone and this aqueous phase quencher, while addition of alcohols inhibits this protective effect. This again suggests that alcohols occupy the space within the β-CD cavity and force nabumetone molecules to reside in the aqueous environment. Based on the significant enhancement of the fluorescence intensity of nabumetone produced through complex formation, a spectrofluorimetric method for the determination of nabumetone in bulk aqueous solution in the presence of β-CD is developed. The linear relationship between the fluorescence intensity and nabumetone concentration was obtained in the range of 0～3.0 μg·mL~(-1), with a correlation coefficient (r) of 0.9997. The detection limit is 1.0 ng·mL~(-1). There is no interference from the excipients normally used in tablet formulations. The application of the present method to the determination of nabumetone in tablets gave satisfactory results and was compared with the reference method.

Key words: cyclodextrin, nabumetone, FLUOROSPECTROPHOTOMETRY