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

The absorption and fluorescence emission spectra of cyanidin and cyanidin 3-O-beta-glucopyranoside (Cy3G1c) 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 230 nm and at higher wavelengths at 270 and 280 nm. Cyanidin exhibits fluorescence emission maxima at 310 nm and in the visible range at 615 nm. The most effective fluorescence excitation for the Cy3GIc was at 220 and at 230 nm, and at higher wavelengths at 300 and at 310 nm. The Cy3G1c 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 Cy3G1c, it can be seen that fluorescence emission intensity for cyanidin is significantly higher than that for Cy3G1c. These results revealed the impact of 3-glucosidic substitution at C-3 of aglycone (to form Cy3G1c) on the significantly decrease in fluorescence emission intensity, and disappearance of the fluorescence emission in visible wavelength range.