Crushing Garlic and Slicing Onions: Detection of Sulfenic Acids and Other Reactive Organosulfur Intermediates from Garlic and Other Alliums using Direct Analysis in Real-Time Mass Spectrometry (DART-MS)

Abstract

Direct analysis in real-time mass spectrometry (DART-MS) under both positive-ion (PI) and negative-ion (NI) high-resolution (HR) conditions has been used to identify reactive sulfur-containing compounds formed from cutting seven different genus Allium species, garlic, onion, elephant garlic, leek, Chinese chives, and the ornamental species, Allium siculum and A. stipitatum. From cut garlic, PI-DART-MS shows allicin, allyl/methyl and dimethyl thiosulfinates, diallyl trisulfane S-oxide, allyl alcohol, and propene, whereas NI-DART-MS shows 2-propenesulfenic acid, 2-propenesulfinic acid, SO₂, and pyruvate. From cut onion, PI-DART-MS shows mainly the lachrymatory factor (LF), along with much lower amounts of thiosulfinates, zwiebelanes, and a bis-sulfine. From cut elephant garlic, both allicin and LF are found, along with thiosulfinates and bis-sulfine. From cut leek, using PI-DART-MS, mixed methyl-1-propenyl-n-propyl thiosulfinates are found, whereas cut Chinese chive shows predominantly methyl with lesser amounts of mixed allyl/methyl thiosufinates. From cut A. siculum, PI-DART-MS shows butanethial S-oxide along with lesser amounts of mixed 1-butenyl/n-butyl/methyl thiosulfinates, while from cut A. stipitatum, N-hydroxy-2-pyridinethione (pyrithone) is seen. PI-DART-MS analysis of all six cut Allium species showed that disulfanes and polysulfanes were absent, which is consistent with these compounds being artifacts from handling and analysis.

Keywords:

• Alliums
• DART-MS
• garlic
• sulfenic acids
• sulfines
• trisulfane S-oxide

Acknowledgments

Support from the National Science Foundation (CHE-0744578; E.B.) is gratefully acknowledged.