ALLIUM CHEMISTRY - HPLC ANALYSIS OF THIOSULFINATES FROM ONION, GARLIC, WILD GARLIC (RAMSOMS), LEEK, SCALLION, SHALLOT, ELEPHANT (GREAT-HEADED) GARLIC, CHIVE, AND CHINESE CHIVE - UNIQUELY HIGH ALLYL TO METHYL RATIOS IN SOME GARLIC SAMPLES

Room temperature vacuum distillates and extracts of onion (Allium cepa), garlic (Allium sativum), wild garlic (Allium ursinum), leek (Allium porrum L.), scallion (Allium fistulosum L.), shallot (Allium ascalonicum auct.), elephant (or great-headed) garlic (Allium ampeloprasum L. var. ampeloprasum auct.), chive (Allium schoenoprasum L.), and Chinese chive (Allium tuberosum L.) were analyzed by HPLC and H-1 NMR using authentic samples of suspected thiosulfinate components to evaluate the methods. Of the eight different thiosulfinates separated and identified in each plant extract, several are reported here for the first time. It is concluded that gas chromatography, as typically performed with high injector and column temperatures, presents an erroneous picture of the composition of room temperature extracts from Allium species and that HPLC provides a reliable qualitative and semiquantitative measure of what is actually present. A simple vacuum distillation procedure facilitating qualitative analysis of Allium volatiles is described. A number of significant trends are noted regarding the varying proportions of different thiosulfinates in each Allium species. In particular, some garlic varieties grown in cooler climates show a higher allyl to methyl ratio than garlic grown in warmer climates.