Analytical methods for bioactive sulfur compounds in Allium: An integrated review and future directions

Abstract

Plant organosulfur compounds represent one of the main groups of phytochemicals that evidence an ample spectrum of biological activities. There are two major sources of sulfur-containing compounds in plant foods; Allium vegetables, such as garlic, onion, and leek; and cruciferous vegetables, such as broccoli, cabbage, and cauliflower. Among them, garlic is the most studied species, mainly due to the multiple health-enhancing effects attributed to its consumption. Most of these properties have been attributed to organosulfur compounds. Thus, knowledge on the analytical determinations available for the main bioactive sulfur compounds in Allium is of interest. In the present review, an extensive bibliographic survey was performed to compile information regarding the different methodologies that can be used for the determination of alk(en)yl cysteine sulfoxides (ACSOs), S-allyl cysteine (SAC), thiosulfinates (mainly allicin), diallyl, mono- di-, and tri-sulfides, vinyldithiins and (E)- and (Z)-ajoene, as influenced by plant matrices and other factors. The gathered information was analyzed and presented in a systemic and comparative way, describing advantages and disadvantages of the methodologies, considering both extractive and separative techniques, the type of matrices, columns and analytical performance data. In addition, new trends and future prospects for the analysis of sulfur compounds in plants were critically discussed.