Determination of quinolizidine alkaloids in different Lupinus species by NACE using UV and MS detection

Abstract

Lupin seeds are important for animal and human nutrition. However, they may contain toxic quinolizidine alkaloids (QA). Analytical methods for a reliable alkaloid determination are therefore of importance. Here the presented study reports on the first CE method for the analysis of QA in Lupinus species. A buffer system consisting of 100mM ammonium formate in methanol, acetonitrile, and small amounts of water and acetic acid enabled the baseline separation of sparteine, lupanine, angustifoline and 13alpha-hydroxylupanine in less than 10min. Applied voltage, temperature and detection wavelength were 25kV, 30 degrees C and 210nm, respectively. Additional compounds were identified in CE-MS experiments, in which all alkaloids could be assigned in positive ESI mode at corresponding [M+H](+) values. The CE method was validated for linearity, sensitivity, accuracy and precision, and then used to assess the seeds of seven different Lupinus species for their alkaloid content. Lupanine was present in all of them within a range from 0.02% (L. densiflorus, L. microcarpus) to 1.47% (L. albus). The highest percentage of an individual alkaloid was found in L. polyphyllus (3.28% of angustifoline), the content of total alkaloids ranged from 0.43% (L. microcarpus) to 5.13% in L. polyphyllus. The quantitative results were in good agreement with literature data.