<i>Allium</i> Chemistry: Supercritical Fluid Extraction and LC−APCI−MS of Thiosulfinates and Related Compounds from Homogenates of Garlic, Onion, and Ramp. Identification in Garlic and Ramp and Synthesis of 1-Propanesulfinothioic Acid <i>S</i>-Allyl Ester

Abstract

Supercritical fluid (SF) extracts of homogenized garlic (Allium sativum L.), ramp (A. tricoccum Ait.), and onion (A. cepa) were characterized with liquid chromatography (LC) and atmospheric pressure chemical ionization mass spectrometric identification. The major thiosulfinates from garlic and ramp were readily characterized by this technique. Small quantities of ajoene, a potent antithrombotic agent, were also found in SF extracts of garlic homogenates. The profiles of onion juice extracts revealed the usual thiosulfinates, zwiebelanes, and bissulfine reported in prior studies, as well as cepaenes previously identified in extracts of onion juice through extensive isolation steps and spectroscopic methods. The presence of trace quantities of allyl compounds in onion juice and propyl compounds in garlic and ramp homogenates has been verified by LC−mass spectrometry (MS). The presence of these compounds was not readily evident in previous analyses using gas chromatography−MS with cold-on-column injection and reversed-phase or normal phase LC with UV detection. Keywords: Supercritical fluid extraction; liquid chromatography; mass spectrometry; LC−MS; onion, Allium cepa; garlic, Allium sativum L.; ramp, Allium tricoccum Ait.; thiosulfinates