title: Stereoselective Metabolism of the Sterol Biosynthesis Inhibitor Fungicides Fenpropidin, Fenpropimorph, and Spiroxamine in Grapes, Sugar Beets, and Wheat.
abstract: Metabolism of chiral pesticides in crops is typically studied using achiral analytical methods and, consequently, the stereoisomer composition of residues is unknown. In this study, we developed an enantioselective GC-MS/MS method to quantify residues of the fungicides fenpropidin, fenpropimorph, and spiroxamine in plant matrices. In field trials, the fungicides were applied to grapevines, sugar beets, or wheat. Fenpropidin was metabolized with no or only weak enantioselectivity. For fenpropimorph, slightly enantioselective metabolism was observed in wheat but more pronounced in sugar beets. This enantioselectivity was due to different rates of metabolism and not due to interconversion of enantiomers. The four stereoisomers of spiroxamine were also metabolized at different rates, but selectivity was only found between diastereomers and not between enantiomers. trans-Spiroxamine was preferentially degraded in grapes and cis-spiroxamine in wheat. These findings may affect the consumer dietary risk assessment because toxicological end points were determined using racemic test substances.
authors.affiliation: Institute for Plant Production Sciences, Agroscope , CH-8820 Wädenswil, Switzerland.
authors.forename: Ignaz J
authors.initials: IJ
authors.lastname: Buerge
authors.affiliation: Institute for Plant Production Sciences, Agroscope , CH-8820 Wädenswil, Switzerland.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Krauss
authors.affiliation: IRNAS, Institute of Natural Resources and Agrobiology of Seville , E-41012 Seville, Spain.
authors.forename: Rocío
authors.initials: R
authors.lastname: López-Cabeza
authors.affiliation: Institute for Plant Production Sciences, Agroscope , CH-8820 Wädenswil, Switzerland.
authors.forename: Werner
authors.initials: W
authors.lastname: Siegfried
authors.affiliation: Institute for Plant Production Sciences, Agroscope , CH-8820 Wädenswil, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Stüssi
authors.affiliation: Institute for Sustainability Sciences, Agroscope , CH-8046 Zürich, Switzerland.
authors.forename: Felix E
authors.initials: FE
authors.lastname: Wettstein
authors.affiliation: Institute for Plant Production Sciences, Agroscope , CH-8820 Wädenswil, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Poiger
mesh_terms: D027461:Beta vulgaris / Q000737:chemistry / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D010575:Pesticides / Q000737:chemistry / Q000378:metabolism*; D013141:Spiro Compounds / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D013261:Sterols / Q000096:biosynthesis*; D053719:Tandem Mass Spectrometry; D014908:Triticum / Q000737:chemistry / Q000378:metabolism*; D027843:Vitis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010575:Pesticides; D013141:Spiro Compounds; D013261:Sterols; C510887:spiroxamine
keywords: enantioselective GC-MS; fenpropidin; fenpropimorph; pesticide residues; spiroxamine; stereoselective metabolism; sterol biosynthesis inhibitor