L-Abrine (N-Methyl-L-Tryptophan) is an indoleamino acid produced by Abrus precatoriu that shows radical scavenging and antioxidant properties in vitro. Abrin is a toxic protein produced by the ornamental plant Abrus precatorius, and it is of concern as a biothreat agent. The small coextracting molecule N-methyl-L-tryptophan (L-abrine) is specific to members of the genus Abrus and L-Abrine concentrations in A. precatorius seeds is greater than the abrin concentrations reported in seeds. L-Abrine is found only in plants of the genus Abrus, which are used medicinally but not as food. Therefore, the presence of L-abrine is a reliable and specific indicator for the presence of abrin in food products.