Preparation and purification of garlic-derived organosulfur compound allicin by green methodologies

Abstract

Effective green chemistry, green reversed-phase high-performance liquid chromatography (RP-HPLC), and green thin layer chromatography (TLC) methods used for preparing and purifying allicin, a garlic-derived organosulfur compound, are described here. A greener version of the acidic oxidation reaction of diallyl disulfide (DADS) is used to produce allicin with high yield. Green RP-HPLC eliminates the liquid/liquid extraction step from either the DADS acidic oxidation reaction mixture or from garlic extract, allowing the single-step purification of allicin. The proposed method involved the use of eco-friendly ethanol as the alternative eluent for acetonitrile. The pure allicin HPLC fraction prepared this way is quite stable and can be used directly for chemical and biological applications. In addition, by changing silica gel TLC plate to RP-C18 TLC plate, 50∈% aqueous ethanol, instead of a solvent blend of hexane: isopropanol (92:8) can be used to identify the allicin on TLC plate. Here, the traditional usage of toxic organic solvents has been avoided and a more efficient chemical reaction scheme is employed, which permits the classification of the present method as green. These green methodologies are used successfully to prepare pure allicin, investigate the thermal, pH, and vacuum drying decomposition of the allicin, and analyze various preparations of garlic extract.