A tissue homogenate method to prepare gram-scale Allium thiosulfinates and their disulfide conjugates with cysteine and glutathione.

The health benefits of Allium vegetables are widely attributed to the enzyme-derived organosulfur compounds called thiosulfinates (TS). However, the lack of a suitable method to prepare TS in good yields has hampered the evaluation of their biological activities. This paper describe a simple enzymatic method using Allium tissue homogenates as a reaction system to prepare gram-scale TS, including those enriched in 1-propenyl groups, which are particularly difficult to obtain. This method is simple, easy to scale up, and requires no column purification step, making it suitable for practical large-scale production of Allium TS. The prepared TS were further utilized to prepare the disulfide conjugates with cysteine and glutathione (CySSR and GSSR, R = methyl, ethyl, propyl, 1-propenyl, and allyl), which are the presumptive metabolites of TS. Among all of the Allium CySSR and GSSR conjugates, the newly prepared glutathione conjugate with 1-propenyl TS, GSSPe, showed the most potent effect to induce quinone reductase (QR, a representative phase II enzyme) in murine hepatoma cells (Hepa 1c1c7) and inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated macrophage cells (RAW 264.7).