Subcritical reactive extraction of shogaol and gingerol: Effect of time and temperature

Abstract

Gingerol and shogaol are two bioactive compounds of ginger which exhibit several positive effects on human health. The conventional method for shogaol preparation is considered ineffective because it causes losses to the environmental system, and the efficiency of the process is low. Reactive extraction with subcritical water is a method that is considered environmentally friendly for the separation of slightly polar components without using organic solvents. The advantage of the reactive extraction process with subcritical water is that it does not require a catalyst because the process is able to form hydronium ions which can act as a catalyst to convert shogaol into gingerol. The effect of time and temperature on the yields of subcritical water reactive extraction of gingerol and shogaol were investigated in the present work. Experiments were carried out at a fixed pressure of 2 bar, and a varied temperature of reactive extraction from 130 to 140°C. Ginger and shogaol contents were analysed from the samples every 10 min. The chemical profiling of the resulting ginger extracts was performed using HPLC-MS. Results showed that the best subcritical water process was at 2 bar, 130°C, and 20 min; shogaol concentration increased to 15.345%, and gingerol to 5.113%. For the reactive extraction time of longer than 20 min, the shogaol concentration of the extract decreased. When temperature was above 120°C, and water hydrogen bonds weakened, thus resulting in high amounts of ionisation products of subcritical water.