L-(+)-Abrine (L-Abrine)

Quantification of L-abrine in human and rat urine: a biomarker for the toxin abrin

Abrin is a toxic protein found in the jequirity seed. L-Abrine (N-methyl-tryptophan) is also found in the jequirity seed and can be used as a biomarker for abrin exposure. Analysis of L-abrine was added to an existing method for quantifying ricinine as a marker for ricin exposure in human urine and analytically validated. Accuracy and reproducibility were enhanced by including a newly synthesized (13)C(1)(2)H(3)-L-abrine internal standard. One-milliliter urine samples were processed using solid-phase extraction prior to a 6-min high-performance liquid chromatography separation. Protonated molecular ions were formed via electrospray ionization in a triple-quadrupole mass spectrometer and quantified via multiple reaction monitoring. Method validation included the characterization of two enriched urine pools, which were used as quality control materials. Endogenous levels of L-abrine were quantified in a reference range of 113 random urine samples at 0.72 +/- 0.51 ng/mL. Urinary concentrations of L-abrine were monitored in an intentional rat exposure study for up to 48 h. Comparing the results from the human reference range and the animal exposure study indicates that this method is suitable for quantifying L-abrine within 24 h post-exposure. Quantification of L-abrine beyond 24 h is limited by rapid excretion of the biomarker and the level of the L-abrine dose.

Isolation, Solid-state Structure Determination, In Silico and In Vitro Anticancer Evaluation of an Indole Amino Acid Alkaloid L-Abrine

Background: Abrus precatorius Linn. (Kunch in Bengali) is widely spread in tropical and sub-tropical regions. It is a typical plant species which is well-known simultaneously as folk medicine and for its toxicity.
Objective: Phytoceutical investigation of the white variety seeds of Abrus precatorius Linn.
Methods: Traditional extraction, separation, isolation, and purification processes were followed. The structure was elucidated by various spectral analyses and the solid-state structure of this indolealkaloid was determined by X-ray crystallographic analysis. Docking interactions of L-abrine had been studied against ten major proteins, responsible for various types of cancers. In silico studies were done by Schr?dinger Maestro, AutoDock4, PyMOL and AutoDock Vina. The protein structures were downloaded from Protein Data Bank. Sulforhodamine B (SRB) colorimetric assay was used for in vitro anticancer evaluation against four human cancer cell lines.
Results: An indole-containing unusual amino acid alkaloid had been isolated from the white variety seeds of Abrus precatorius Linn. In silico docking studies demonstrated significant antiproliferative activity against four human cancer cell lines.
Conclusion: The solid-state zwitterion structure of the indole-containing alkaloid (α-methylamino- β-indolepropionic acid, L-abrine) has been confirmed for the first time by X-ray crystallography. Highly promising in silico and in vitro results indicate that L-abrine may find its space in future anticancer drug discovery research.

Rapid method using two microbial enzymes for detection of L-abrine in food as a marker for the toxic protein abrin

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 thus can be used as a marker for the presence or ingestion of abrin. Current methods for the detection of abrin or l-abrine in foods and other matrices require complex sample preparation and expensive instrumentation. To develop a fast and portable method for the detection of l-abrine in beverages and foods, the Escherichia coli proteins N-methyltryptophan oxidase (MTOX) and tryptophanase were expressed and purified. The two enzymes jointly degraded l-abrine to products that included ammonia and indole, and colorimetric assays for the detection of those analytes in beverage and food samples were evaluated. An indole assay using a modified version of Ehrlich's/Kovac's reagent was more sensitive and less subject to negative interferences from components in the samples than the Berthelot ammonia assay. The two enzymes were added into food and beverage samples spiked with l-abrine, and indole was detected as a degradation product, with the visual lower detection limit being 2.5 to 10.0 μM (?0.6 to 2.2 ppm) l-abrine in the samples tested. Results could be obtained in as little as 15 min. Sample preparation was limited to pH adjustment of some samples. Visual detection was found to be about as sensitive as detection with a spectrophotometer, especially in milk-based matrices.

A case of abrin toxin poisoning, confirmed via quantitation of L-abrine (N-methyl-L-tryptophan) biomarker

Introduction: The seeds of Abrus precatorius contain the highly toxic plant protein abrin. There is no antidote for abrin poisoning. Management, largely supportive, may consist of administering intravenous fluids, anti-emetics, and activated charcoal depending on the time of exposure. We report the presentation of a single case of unintentional abrin poisoning confirmed by the quantitation of L-abrine biomarker.
Case report: A previously healthy 22-month-old, 11.5-kg female presented to the hospital after ingesting approximately 20 rosary peas (A. precatorius) sold as a "peace bracelet". Her primary manifestations were episodes of forceful emesis that included food particles progressing to clear gastric fluid. The patient was tachycardic (HR = 134 bpm) but had brisk capillary refill and normal blood pressure (96/60 mmHg). Laboratory testing revealed elevated blood urea nitrogen (16 mg/dL) and serum creatinine (0.4 mg/dL). In the emergency department, the patient was resuscitated with 40 mL/kg normal saline via peripheral IV and received ondansetron (0.15 mg/kg IV) to control retching. The patient was discharged well 24 h after the ingestion.
Discussion: This is the first case of human abrin toxin poisoning confirmed by the quantitation of L-abrine as a biomarker. Quantifying the levels of abrin toxin in the body after exposure can help clinicians make informed decisions when managing patients with symptomatic exposures to seeds of A. precatorius.

Metabolomic Characterization of Acute Ischemic Stroke Facilitates Metabolomic Biomarker Discovery

Acute ischemic stroke (AIS) is characterized by a sudden blockage of one of the main arteries supplying blood to the brain, leading to insufficient oxygen and nutrients for brain cells to function properly. Unfortunately, metabolic alterations in the biofluids with AIS are still not well understood. In this study, we performed high-throughput target metabolic analysis on 44 serum samples, including 22 from AIS patients and 22 from healthy controls. Multiple-reaction monitoring analysis of 180 common metabolites revealed a total of 29 metabolites that changed significantly (VIP > 1, p < 0.05). Multivariate statistical analysis unraveled a striking separation between AIS patients and healthy controls. Comparing the AIS group with the control group, the contents of argininosuccinic acid, beta-D-glucosamine, glycerophosphocholine, L-abrine, and L-pipecolic acid were remarkably downregulated in AIS patients. Twenty-nine out of 112 detected metabolites enriched in disturbed metabolic pathways, including aminoacyl-tRNA biosynthesis, glycerophospholipid metabolism, lysine degradation, phenylalanine, tyrosine, and tryptophan biosynthesis metabolic pathways. Collectively, these results will provide a sensitive, feasible diagnostic prospect for AIS patients.