Ultraviolet fluorescence of cyanidin and malvidin glycosides in aqueous environment

The fluorescence of cyanidin 3-glucoside (Cy 3-glc), cyanidin 3,5-diglucoside (Cy 3,5-diglc) and malvidin 3,5-diglucoside (Mv 3,5-diglc) in binary solvents (water-methanol, 1:1, v/v) and in water at pH 4-5.5 has been studied. The absorption spectra, steady-state fluorescence spectra, and fluorescence excitation spectra have been measured. Fluorescence excitation was in the UV range at the absorption maxima of cyanidin and malvidin glycosides (lambda(exc) = 220 nm) and at the characteristic absorption band of about lambda(exc) = 280 nm. In the aqueous environment, Cy 3-glc exhibits short-wavelength fluorescence F-SH at lambda(fl)(max) = 299 nm which was most effectively excited at 220 nm. Similar short-wavelength fluorescence F-SH was observed for Cy 3,5-diglc (lambda(fl)(max) = 308 nm) and Mv 3,5-diglc (lambda(fl)(max) = 293 nm) in a binary solvent system.