Quantitative HPLC–MS/MS analysis of toxins in soapberry seeds: Methylenecyclopropylglycine and hypoglycin A

•Quantitates MCPG and HGA levels in soapberry seeds.•Adapts previous platform used to quantitate MCPG and HGA levels in soapberry arils.•Enables public health investigators to determine how ripeness affects MCPG and HGA.•Provides first quantitation of HGA in litchi, mamoncillo, and longan seeds. Methylenecyclcopropylglycine (MCPG) and hypoglycin A (HGA) are naturally occurring amino acids found in various soapberry (Sapindaceae) fruits. These toxins have been linked to illnesses worldwide and were recently implicated in Asian outbreaks of acute hypoglycemic encephalopathy. In a previous joint agricultural and public health investigation, we developed an analytical method capable of evaluating MCPG and HGA concentrations in soapberry fruit arils as well as a clinical method for the urinary metabolites of the toxins. Since the initial soapberry method only analyzed the aril portion of the fruit, we present here the extension of the method to include the fruit seed matrix. This work is the first method to quantitate both MCPG and HGA concentrations in the seeds of soapberry fruit, including those collected during a public health investigation. Further, this is the first quantitation of HGA in litchi seeds as well as both toxins in mamoncillo and longan seeds.