Development and validation of a rapid and sensitive LC-MS/MS approach for alkaloid testing in different Lupinus species

Foods derived from lupin are attracting consumers and producers for their nutritional value and low cost of production. Lupin products may pose a health risk to consumers due to the presence of toxic alkaloid compounds. To monitor alkaloids in lupin seeds, we developed and validated a rapid LC-MS/MS method for the determination of five quinolizidine alkaloids and one indole alkaloid in lupin seeds. The final method involves extraction by water/acetonitrile, ultrasonication, separation using NaCl and MgSO4, alkalinisation by NaOH and analysis using HPLC-MS/MS. The separation was achieved in 6 min using HPLC directly coupled to MS/MS on a 6500 + QTRAP in ESI-positive mode. The method showed acceptable recovery for all tested compounds in soybean grain at a wide range from 0.55 (LOQ) to 55 mg/kg, with a mean recovery of 93% for the total alkaloid content (SD <2.5%). The method was tested on a commercial lupin flour sample yielding an alkaloid concentration of 130 mg/kg (SD 3.6%). Alkaloid profiles were assessed across different cultivars of five Lupinus species (Lupinus angustifolius, L. cosentinii, L. albus, L. luteus, and L. mutabilis). Using the method presented, toxic alkaloid levels can be monitored in lupin-based products to ensure their safety for human consumption. The method was deployed to measure the alkaloid content across different seeds of narrow-leaf lupin from the same farm, revealing that the alkaloid content varied widely from seed to seed from the same farm.