Isolation of the sweet components from Siraitia grosvenorii

Abstract

Powdered concentrate from dried Luo Han Guo fruit was subjected to liquid extraction by Soxhlet (hexane:ethanol, 1/4 v/v) or with subcritical water (scH 2O) or with supercritical ethanol carbon dioxide (scCO 2). Whereas exhaustive Soxhlet extraction of the crude dried fruit powder (CDFP) was inefficient, pressurized water extraction in the presence of chromatographic support (Alumina, Celite or Silica gel) was beneficial to the scH 2O recovery of mogrosides as determined by colourimetry. With a flow rate of 0.7 mL min −1 scH 2O and a back pressure of 11.7 MPa, a maximum recovery was obtained at 150 °C; yet increases in recovery for extractions beyond 10 min were marginal. The recovery of target compounds were very inefficient for scCO 2 alone but was improved with the addition of 0.3 mL min −1 ethanol as co-solvent to the mobile phase and by adding chromatographic support to the substrate. Increased pressure during the scCO 2 extractions were beneficial to the recoveries that were maximized at 60 °C. However, increases in the recoveries of mogrosides for extractions beyond 90 min for the dried fruit powder or beyond 30 min for the partially purified concentrate were very modest. Of the three extraction techniques, Soxhlet, scCO 2 or scH 2O, the latter technique, in tandem with ultra-sonication of the dried fruit powder proved to be very efficient so that there was little value to partially purifying this substrate prior to pressurized fluid extraction.