An insight into cyclocurcumin cis–trans isomerization: Kinetics in solution and in the presence of silver nanoparticles

Abstract

Cyclocurcumin (CyCUR) is a non-diarylheptanoid curcuminoid characterized by an α,β-unsaturated dihydropyranone moiety generally existing as trans isomer in the ground state but able to convert into the cis form by photoisomerization. Herein the kinetics of thermal cis–trans isomerization of cyclocurcumin was spectroscopically determined in ethanol, pure water and silver nanoparticles (AgNPs) aqueous solution. Energetic parameters were calculated by Arrhenius and Eyring plots in the temperature range 294–314 K. The presence of AgNPs increases the rate of the reaction, according to the polarizability of the environment. The solvatochromism of cyclocurcumin was also studied by using the Catalán empirical solvent parameters scale in a series of organic solvents. The bathochromic shift of CyCUR suggests that polarizability of the medium plays the major role in the investigated conditions.