Title: Ajothiolanes: 3,4-Dimethylthiolane Natural Products from Garlic (Allium sativum)

Abstract

Stereoisomers of 5-(2-allylsulfinyl)-3,4-dimethylthiolane-2-ol, a family of 3,4-dimethylthiolanes of formula C₉H₁₆O₂S₂ we name ajothiolanes, were isolated from garlic (Allium sativum) macerates and characterized by a variety of analytical and spectroscopic techniques, including ultraperformance liquid chromatography (UPLC), direct analysis in real time-mass spectrometry (DART-MS), and liquid chromatography–tandem mass spectrometry (LC-MS/MS). Ajothiolanes were found to be spectroscopically identical to a family of previously described compounds named garlicnins B_1–4 (C₉H₁₆O₂S₂), whose structures we demonstrate have been misassigned. 2D ¹³C–¹³C NMR incredible natural abundance double quantum transfer experiments (INADEQUATE) were used to disprove the claim of nine contiguous carbons in these compounds, while X-ray absorption spectroscopy (XAS) along with computational modeling was used to disprove the claim that these compounds were thiolanesulfenic acids. On the basis of the similarity of their NMR spectra to those of the ajothiolanes, we propose that the structures of previously described, biologically active onionins A_1–3 (C₉H₁₆O₂S₂), from extracts of onion (Allium cepa) and Allium fistulosum, and garlicnin A (C₁₂H₂₀O₂S₄), from garlic extracts, should also be reassigned, in each case as isomeric mixtures of 5-substituted-3,4-dimethylthiolane-2-ols. We conclude that 3,4-dimethylthiolanes may be a common motif in Allium chemistry. Finally, we show that another garlic extract component, garlicnin D (C₇H₁₂O₂S₃), claimed to havemore » an unprecedented structure, is in fact a known compound from garlic with a structure different from that proposed, namely, 2(E)-3-(methylsulfinyl)-2-propenyl 2-propenyl disulfide.« less

Authors:

Block, Eric  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-4668-1687"

Dethier, Bérénice ^[1]; Bechand, Benjamin ^[1]; Cotelesage, Julien J. H. ^[2]; George, Graham N.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-0420-7493"

Goto, Kei ^[3]; Pickering, Ingrid J.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-0936-2994"

Mendoza Rengifo, Emerita ^[2]; Sheridan, Robert ^[4]; Sneeden, Eileen Y. ^[5]; Vogt, Linda ^[2]

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+ Show Author Affiliations

1. State Univ. of New York, Albany, NY (United States). Dept. of Chemistry
2. Univ. of Saskatchewan, Saskatoon, SK (Canada). Dept. of Geological Sciences
3. Tokyo Inst. of Technology, Tokyo (Japan). Dept. of Chemistry
4. NYS Dept. of Agriculture and Markets, Albany, NY (United States). Food Laboratory Division
5. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)

Publication Date:

Sun Sep 09 00:00:00 EDT 2018

Research Org.:

SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Institutes of Health (NIH)

OSTI Identifier:

1490686

Grant/Contract Number:  

AC02-76SF00515; GM57375; 5R01 DC014423-02; P41GM103393; CHE-0744578; CHE-1429329; CHE-1265679

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Agricultural and Food Chemistry

Additional Journal Information:

Journal Volume: 66; Journal Issue: 39; Journal ID: ISSN 0021-8561

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 3,4-dimethylthiolanes; ajothiolane; Allium cepa; Allium fistulosum; Allium sativum; DART-MS; garlic; INADEQUATE NMR; naturally occurring thiolanes; onion; sulfenic acids; thiolane-2-ol; UPLC; X-ray absorption spectroscopy