Investigation of fluorescence properties of cyanidin and cyanidin 3-o-β-glucopyranoside

The absorption and fluorescence emission spectra of cyanidin and cyanidin 3-O-β-glucopyranoside (Cy3Glc) at pH 5.5 in aqueous solution have been studied. The most effective fluorescence excitations of cyanidin were at the UV absorption maxima at 220 and at 230 nm and at higher wavelengths at 270 and at 280 nm. Cyanidin exhibits fluorescence emission maxima at 310 nm and in the visible range at 615 nm. For the Cy3Glc most effective fluorescence excitation was at 220 and at 230 nm and at higher wavelengths at 300 and at 310 nm. Cy3Glc has fluorescence emission spectra with the maximum at 380 nm and does not show fluorescence emission in the visible range. If compare fluorescence emission spectra of cyanidin and Cy3Glc it can be seen that fluorescence emission intensity for cyanidin is significantly higher than that for Cy3Glc. These results reveals the impact of 3-glucosidic substitution at C-3 of aglycone (to form Cy3Glc) on the significantly decrease in fluorescence emission intensity, and disappearance of the fluorescence emission in visible wavelength range