Off-Line Supercritical Fluid Extraction of Thiosulfinates from Garlic and Onion

Supercritical fluid (SF) extracts of fresh garlic (Allium sativum) and fresh onion (Allium cepa) were analyzed by liquid chromatography, gas chromatography (GC), and mass spectrometry (MS). Allicin (2-propene-1-sulfinothioic acid S-2-propenyl ester), the major thiosulfinate found in fresh garlic, was readily extracted by using supercritical CO2 (SC-CO2). Under SF extraction conditions using a solvent trap, the yield of allicin from a water homogenate of fresh garlic was 98.2%; however, when a solid-phase trap (i.e., condensation on glass beads) was used, the yield of allicin was 124.6% relative to yields obtained with methylene chloride extraction. An increase in the quantity of thermal decomposition products with respect to allicin was evident when the garlic was extracted at temperatures greater than 36 degrees C. The identity of allicin in the garlic SF extracts was confirmed by thermospray MS. The SF extraction of yellow onion was ca. 69% as efficient as the extraction with diethyl ether, as determined by GC-MS