title: Precursors and formation of pyrithione and other pyridyl-containing sulfur compounds in drumstick onion, Allium stipitatum.
abstract: Two novel, structurally unusual cysteine derivatives were isolated from the bulbs of Allium stipitatum (Allium subg. Melanocrommyum) and shown to be S-(2-pyridyl)cysteine N-oxide and S-(2-pyridyl)glutathione N-oxide. The former compound is the first example of a naturally occurring alliinase substrate that contains an N-oxide functionality instead of the S-oxide group. In addition, S-methylcysteine S-oxide (methiin) and S-(methylthiomethyl)cysteine 4-oxide (marasmin) were found in the bulbs. Presented data suggest that the previously reported identification of S-(2-pyridyl)cysteine S-oxide was most likely erroneous. The alliinase-mediated formation of pyridyl-containing compounds following disruption of A. stipitatum bulbs was studied by a combination of HPLC-MS, HPLC-PDA, DART-MS, and NMR techniques. It was found that no pyridyl-containing thiosulfinates are present in homogenized bulbs in detectable quantities. Instead, various pyridine N-oxide derivatives are formed, including N-hydroxypyridine-2(1H)-thione (pyrithione), 2-(methyldithio)pyridine N-oxide, 2-[(methylthio)methyldithio]pyridine N-oxide, di(2-pyridyl) disulfide N-oxide, and di(2-pyridyl) disulfide N,N'-dioxide. This represents the first report of pyrithione formation as a natural product.
authors.affiliation: Department of Applied Chemistry, University of South Bohemia, České Budějovice, Czech Republic. kubecr@centrum.cz
authors.forename: Roman
authors.initials: R
authors.lastname: Kubec
authors.forename: Petra
authors.initials: P
authors.lastname: Krejcová
authors.forename: Petr
authors.initials: P
authors.lastname: Simek
authors.forename: Lukás
authors.initials: L
authors.lastname: Václavík
authors.forename: Jana
authors.initials: J
authors.lastname: Hajslová
authors.forename: Jan
authors.initials: J
authors.lastname: Schraml
mesh_terms: D000490:Allium / Q000737:chemistry*; D013437:Carbon-Sulfur Lyases / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D018517:Plant Roots / Q000737:chemistry* / Q000378:metabolism; D011725:Pyridines / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013457:Sulfur Compounds / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D013871:Thiones / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011725:Pyridines; D013457:Sulfur Compounds; D013871:Thiones; C008704:pyrithione; D013437:Carbon-Sulfur Lyases; C019243:alliin lyase