Spectroscopic study of molecular associations between riboflavin and some β-carboline derivatives

Abstract

The formation of molecular complexes between riboflavin (RFN) and some β-carboline derivatives (antidepressant drugs that have a pronounced inhibition of monoamine oxidase) has been studied by using electronic absorption and fluorescence spectroscopic methods in aqueous solution. The formation constants for the molecular complexes were determined from data of absorption, using the Foster–Hammick–Wardley method. The quenching phenomenon observed in RFN fluorescence is related to the concentration of the β-carboline derivatives, allowing the calculation of the quenching constants for RFN–β-carboline complexes. Thermodynamic parameters have been determined from the values of associations constants for the molecular complexes at various temperatures. The influence of substituents in the β-carboline molecule on the stability of the complexes formed was also investigated.