S-Methylcysteine sulfoxide explained

S-Methylcysteine sulfoxide is an organosulfur compound with the formula . It is the sulfoxide of S-methylcysteine. It contributes to the flavor of onions (Allium sp.).^{[1] [2]} The compound is usually encountered as one diastereoisomer, the (R)- and (S)-configurations at the carbon and sulfur stereocenters, respectively. The S-methyl part of the name refers to the location of the methyl group on sulfur. Although odorless, S-methylcysteine sulfoxide is acted upon by alliinase and lachrymatory-factor synthase.

S-Methylcysteine sulfoxide is produced from glutathione.^[3]

Related compounds are the unsaturated sulfoxides S-trans-prop-1-enyl cysteine sulfoxide and S-propyl cysteine sulfoxide, both found also in onions, and S-allyl cysteine sulfoxide, typically found in garlic.^[3]

References

1. 10.1016/j.chroma.2009.08.032 . Chromatographic methods for Determination of S-substituted cysteine derivatives—A comparative study . 2009 . Kubec . Roman . Dadáková . Eva . Journal of Chromatography A . 1216 . 41 . 6957–6963 . 19733357 .
2. 23020262 . 2012 . Bernaert . N. . Goetghebeur . L. . De Clercq . H. . De Loose . M. . Daeseleire . E. . Van Pamel . E. . Van Bockstaele . E. . Van Droogenbroeck . B. . Influence of Cultivar and Harvest Time on the Amounts of Isoalliin and Methiin in Leek (Allium ampeloprasum var. porrum). . Journal of Agricultural and Food Chemistry . 60 . 44 . 10910–10919 . 10.1021/jf302132a .
3. 10.1093/jxb/erh138 . Biosynthesis of the flavour precursors of onion and garlic . 2004 . Jones . M. G. . Hughes . J. . Tregova . A. . Milne . J. . Tomsett . A. B. . Collin . H. A. . Journal of Experimental Botany . 55 . 404 . 1903–1918 . 15234988 .