Allium chemistry: GC-MS analysis of thiosulfinates and related compounds from onion, leek, scallion, shallot, chive, and Chinese chive

Extracts of onion (Allium cepa), leek (Allium porrum L.), scallion (Allium fistulosum L.), shallot (Allium ascalonicum auct.), chive (Allium schoenoprasum L.), and Chinese chive (Allium tuberosum L.) were analyzed by GC-MS using wide-bore capillary columns (0.53 mm i.d.) with cryogenic (0 degree C) on-column injection and initial column temperature conditions, slow column heating rates (2-5 degrees C/ min), and GC-MS stransfer line temperatures of 80-100 degrees C. Authentic samples of suspected components were used to verify identities and quantitate amounts, employing benzyl alcohol as internal standard. Under these conditions, thiosulfinates MeS(O)SMe 18), PrS(O)SPr (9), MESS(O)PR (13), MES(O)SPr (14), (Z)- and (E)-MeS(O)SCH==CHMe (12,15), (E)-MeSS(O)CH=CHMe (10), and (Z)- and (E)- PrS(O)SCH=CHMe (6,8) and 2,3-dimethyl-5,6-dithiabicyclo[2.1.1]lhexane 5-oxides (31, 30; cis- and trans-zwiebelanes) were all identified in onion, leek, scallion, shallot, and chive while MeS(O)SMe and (E,Z)-MeS(O)SCH=-CHMe were identified in Chinese chive. On the other hand, we could not obtain satisfactory peaks for MeCH-CHS(O)SPr isomers or any thiosulfinates containing a 2-propenyl (allyl) group, which are beet identified by HPLC. Sensory data are provided on compounds 30 and 31