Post-Mortem Changes of Methomyl in Blood with Hemoglobin

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Biochemistry

Background:

• Methomyl is a common pesticide implicated in fatal poisonings.
• Low blood methomyl concentrations in deceased individuals pose a challenge for forensic analysis.
• Previous hypotheses suggested methomyl decomposition or protein binding as causes for low recovery.

Purpose of the Study:

• To investigate the reasons for the insufficient recovery of methomyl in blood.
• To identify specific mechanisms of methomyl interaction with blood components.
• To explore potential biomarkers for methomyl poisoning.

Main Methods:

• Incubation of methomyl with human serum albumin to test for esterase activity.
• Detection and characterization of methomyl-protein adducts using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q/TOF-MS).
• Quantification of methomyl adducts in vitro and in blood samples from an autopsy case.

Main Results:

• Human serum albumin did not exhibit esterase activity towards methomyl.
• Specific methomyl-hemoglobin adducts were identified, primarily involving tryptophan, tyrosine, and valine residues.
• The formation of tryptophan and valine adducts increased dose-dependently in vitro.
• The tryptophan adduct was detected in blood from a methomyl poisoning victim.

Conclusions:

• Methomyl does not decompose via serum albumin esterase activity.
• Methomyl specifically binds to hemoglobin, forming detectable adducts.
• The methomyl-tryptophan hemoglobin adduct is a potential biomarker for methomyl poisoning.
• Quantification of the tryptophan adduct allows for estimation of ingested methomyl dose.