Synthesis of novel pyrano-3,7-deoxyanthocyanin derivatives and study of their thermodynamic, photophysical and cytotoxicity properties

Pyranoflavylium-derived compounds have been shown to have improved properties over the corresponding flavylium precursors, such as chemical and photochemical stability. In addition, they have the characteristic of responding to stimuli like pH due to the proton transfer reactions leading to different colored quinoidal bases. Thus, these dyes can be used as powerful pH-indicators for several sensing applications. In this work, the thermodynamic constants and photophysical properties of novel pyrano-3,7-deoxyanthocyanin dyes bearing phenol and catechol groups were studied by UV-vis absorbance and fluorescence measurements as a function of pH. The cytotoxicity properties of these compounds were also evaluated. Overall, the symmetrical phenol-based pyranoflavylium dye showed the greatest color variation within pH range of food spoilage process, remarkable fluorescence properties, and reduced cytotoxicity, which make it a promising candidate as a pH-dependent colorimetric and fluorescence sensor for food intelligent packaging.