Microwave-assisted extraction used for the isolation of total triterpenoid saponins from Ganoderma atrum

In this paper, a method of microwave-assisted extraction (MAE) was for the first time used to extract total triterpenoid saponins from Ganoderma atrum, which have been reported to have several medicinal properties and uses. The extracts were directly determined by colorimetric method without any further treatment. Compared with shaking extraction method, heat reflux extraction, supercritical fluid carbon dioxide extraction (SFE) and normal ultrasound-assisted extraction (UAE), MAE only need 5 min to give the highest yield of triterpenoid saponins at 0.968%, while the other extraction methods need several hours or even more than 10 h and give lower yield. Several factors affecting the MAE extraction rate were also discussed, such as extraction time, temperature, ratio of solvent to material and the kind of solvents. Optimal conditions of MAE can be concluded as follows: 5 min at 90 degrees C, the ratio of solvent to material is 25 by using 95% ethanol as the solvent. (c) 2006 Elsevier Ltd. All rights reserved.