Kinetic studies of the thermal degradation of sulforaphane and its hydroxypropyl-β-cyclodextrin inclusion complex

•The stability of SF and SF/HP-β-CD at various pHs and temperatures was studied.•The SF and SF/HP-β-CD degradation was observed to follow first order kinetics.•The main dynamic parameters of SF and SF/HP-β-CD at various pHs were estimated.•The models to describe the retention ratio at different pH values were proposed.

Sulforaphane (SF) has been of increasing interest for nutraceutical and pharmaceutical industries due to its anti-cancer effect, but it is very sensitive to changes in the temperature and pH. In the present work, pure SF and inclusion complex of SF with hydroxypropyl-β-cyclodextrin (SF/HP-β-CD) were prepared, the depletion rates of SF and SF/HP-β-CD were investigated at temperatures of 60, 75, 82 and 90 °C and pH values of 2.2, 3.0, 4.0, 5.0 and 6.0. The results showed that SF and SF/HP-β-CD were more stable at lower pH values and temperatures, and SF/HP-β-CD was more stable than SF. The SF and SF/HP-β-CD degradation was observed to follow first order kinetics, and the temperature-dependent rate constants for SF and SF/HP-β-CD inclusion complex in aqueous solution were well described by the Arrhenius equation with corresponding activation energies of 70.7 to 94.5 kJ/mol, depending on the pH values. Finally, models to describe the retention ratio of SF and SF/HP-β-CD at different pH values, depletion time and temperatures were proposed.