文摘
The effect of inclusion complex formation on the fluorescence properties of berberine, a clinically importantnatural alkaloid, was studied using cucurbit[7]uril as macrocyclic host compound. The formation of a verystable 1:1 inclusion complex led to about 500-fold fluorescence intensity enhancement, which facilitated thedetection of berberine even below nanomolar concentration. Addition of NaCl caused a significant change inthe association constant and the fluorescence characteristics of the complex, whereas the variation of theanion had a small effect. 1-Alkyl-3-methylimidazolium type ionic liquids altered the fluorescent propertiesof the berberine-cucurbit[7]uril complex much more efficiently than did NaCl. Time-resolved fluorescencestudies showed ternary complex formation. Because berberine fluorescence is insensitive to pH and increasessubstantially upon inclusion in cucurbit[7]uril, the reversible self-assembly of this host-guest pair may findanalytical application in enzyme assays.