Subcritical water extraction of 6-gingerol and 6-shogaol from zingiber officinale

Abstract

Nowadays, natural products extract as a nutritional supplement becomes a part of healthy lifestyle. However, numerous scientific evidences suggested that the processing methods that mainly use organic solvents in extraction processes may result an undesired toxic residues in the product. Thus, the so called ‘green’ solvent that is water seems to be best alternative to substitute the organic solvent in the natural herb extraction process. In this study, the effect of subcritical water extraction (SWE) was employed for the extraction of bioactive compounds from zingiber officinale namely 6-gingerol, 6-shogaol and 10-gingerol. Two types of SWE equipment which are ASE 200 and CLEAR SWE prototype had been utilized. The ASE 200 with the capacity of 24 ml was used to evaluate the performance of the CLEAR SWE prototype with capacity of 1000 ml. Three parameters were manipulated in the SWE optimization process that are extraction temperature (100 to 200°C), static extraction time (10-60 minutes) and solvent to sample ratio (28/3-28/1 ml/g) at a fixed pressure of 3.5 MPa. The analysis was done using the High Performance Liquid Chromatography. Two main bioactive compounds namely 6- gingerol and 6-shogaol were extracted with the traces of 10-gingerol. The extraction and fractionation of 6-gingerol and 6-shogaol were obtained at the lower and higher temperature; respectively. The optimum conditions for the 6-gingerol was at the temperature of 130°C, in 30 minutes and solvent to sample ratio of 28/2 ml/g with the overall mass transfer coefficient of 8.1179 x10 -7 m/s. Meanwhile the optimum condition for the 6-shogaol was at the temperature of 170°C, in 20 minutes and solvent to ratio of 28/2 ml/g with the overall mass transfer coefficient of 18.3764 x 10-7 m/s. It is found that the ginger bioactive compounds will be started to degrade at a temperature above 180 °C.