Interaction of fisetin with human serum albumin by fluorescence, circular dichroism spectroscopy and DFT calculations: binding parameters and conformational changes

► Fisetin-BSA system was studied by fluorescence spectroscopy. ► Binding parameters, association constant and number of sites were estimated. ► Binding site of fisetin was identified by competitive experiments. ► Conformational changes in HSA and fisetin were evidenced by circular dichroism. ► TDDFT calculated CD spectra supported the experimental data.