Supercritical fluid extraction and liquid chromatographic-electrospray mass spectrometric analysis of stevioside from Stevia rebaudiana leaves

Optimal conditions were developed for the HPLC-ESI-MS and supercritical fluid extraction of stevioside from Stevia rebaudiana leaves. In the HPLC-ESI-MS of this compound, the negative ion mode showed higher sensitivity than both UV and the positive ion mode. In developing an alternative extraction method for stevioside using SFE, the effect of temperature, pressure, and percentage of modifier was evaluated on the extraction yield. Although sufficient extractability was not obtained by pure CO2 under any conditions of temperature and pressure, the addition of a modifier dramatically improved the extraction yield of stevioside, making it comparable to organic solvent extraction. Among the modifiers evaluated, the mixture of methanol and water showed greater extraction efficiency than the others. The extraction yield by CO2-methanol-water (80:16:4) was found to be 150% of conventional organic extraction. In addition to improving the extraction yield, SFE obviously provided a higher purity of stevioside in the final extract.