L-(+)-Abrine is a marker for abrin poisoning. A strong indication for abrin poisoning is the presence of the chemical maker L-(+)-Abrine, which can survive metabolism in significant amounts making it detectable in human urine.

Abrin is a toxic protein found in the jequirity seed. L-(+)-Abrine (L-Abrine) is also found in the jequirity seed and can be used as a biomarker for abrin exposure. An animal study is designed to monitor the excretion and recovery of L-(+)-Abrine in 20 rats. The animals are exposed to one of three concentrations of L-(+)-Abrine, a single high concentration of L-tryptophan, or no agent (control). The low L-(+)-Abrine dose corresponds to 0.63 LD ₅₀ i.p. abrin in mice, assuming a concentration ratio of 1:4 of abrin to L-(+)-Abrine and an LD ₅₀ for abrin of 20 μg/kg. The mid and high L-(+)-Abrine (250 and 400 μg/kg) doses are included to ensure that the target analyte can be detected and tracked over the course of the experiment.