Identification of fonofos metabolites in Latuca sativa, Beta vulgaris, and Triticum aestivum by packed capillary flow fast atom bombardment tandem mass spectrometry.
The metabolism of fonofos, a thiophosphonate insecticide, was investigated in mature lettuce (Latuca sativa), beet (Beta vulgaris), and wheat (Triticum aestivum). Six new metabolites were identified by LC-MS and LC-MS-MS analysis using fast atom bombardment (FAB) and packed capillary LC columns with application of the on-column focusing technique. These methods provided the sensitivity required to identify unknown metabolites that were present in the mature plants at only 20-230 ppb. Structural elucidation was facilitated by use of fonofos labeled with both carbon-14 and carbon-13 in the phenyl ring. In all three plants fonofos was converted to a glucose conjugate of thiophenoxylactic acid. Oxidation of the glucose conjugate gave isomeric sulfoxides in all species examined. Thiophenoxylactic acid was found esterified to malonic acid in lettuce. In beets, S-phenylcysteine was found as its malonic acid amide. A second metabolite unique to beets was N-(malonyl)-[2[(ethoxyethylphosphinothionyl)oxy]phenyl]cysteine. This novel structure was confirmed by synthesis.
Onisko
Bruce C
BC
Syngenta, 1200 South 47th Street, Box 4023, Richmond, California 94804-0023, USA. onibid@earthlink.com
Tambling
Doug R
DR
Gorder
Greg W
GW
Diaz
David G
DG
Ericson
John L
JL
Prisbylla
Mike P
MP
Spillner
Chuck J
CJ
D027461:Beta vulgaris / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D004951:Esterification; D004397:Fonofos / Q000032:analysis* / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D005947:Glucose / Q000378:metabolism; D018545:Lactuca / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008314:Malonates / Q000378:metabolism; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014908:Triticum / Q000737:chemistry*
D008314:Malonates; C030290:malonic acid; D005947:Glucose; D004397:Fonofos