The effect of inclusion complex formation on the fluorescence properties of berberine, a clinically important natural alkaloid, was studied using cucurbituril as macrocyclic host compound. The formation of a very stable 1:1 inclusion complex led to about 500-fold fluorescence intensity enhancement, which facilitated the detection of berberine even below nanomolar concentration. Addition of NaCl caused a significant change in the association constant and the fluorescence characteristics of the complex, whereas the variation of the anion had a small effect. l-Alkyl-3-methylimidazolium type ionic liquids altered the fluorescent properties of the berberine-cucurbituril complex much more efficiently than did NaCl. Time-resolved fluorescence studies showed ternary complex formation. Because berberine fluorescence is insensitive to pH and increases substantially upon inclusion in cucurbituril, the reversible self-assembly of this host - guest pair may find analytical application in enzyme assays.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films