THE ANALYSIS OF S-ALK(EN)YL-L-CYSTEINE SULFOXIDES (FLAVOR PRECURSORS) FROM SPECIES OF ALLIUM BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A method of extraction, purification and separation has been developed for the determination of the alk(en)yl-L-cysteine sulphoxides in species of Allium. Alliinase was inhibited during extraction by the addition of 10 mm hydroxylamine. The sulphoxides were separated from the crude extract by passage through an Amberlite IR 120 anion exchange column (H+ form) eluted with 2 M NH4OH, and further purified by high performance liquid chromatography (HPLC) on two Spherisorb columns S5ODS2 in series. The major sulphoxide component found in garlic was (+)-S-allyl-L-cysteine sulphoxide (> 95%); in onion, trans-(+)S-1-propenyl-L-cysteine sulphoxide accounted for 78% of the total sulphoxides extracted, and in chives (+)-S-methyl-L-cysteine sulphoxide was the major component (65%). The analysis provides a sensitive and routine method for estimating the sulphoxide flavour precursors in the Allium species.