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Characteristic ion clusters as determinants for the identification of pyrrolizidine alkaloid N ‐oxides in pyrrolizidine alkaloid–containing natural products using HPLC–MS analysis
Author(s) -
Ruan Jianqing,
Li Na,
Xia Qingsu,
Fu Peter P.,
Peng Shuying,
Ye Yang,
Lin Ge
Publication year - 2012
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.2969
Subject(s) - chemistry , pyrrolizidine , pyrrolizidine alkaloid , mass spectrum , alkaloid , high performance liquid chromatography , fragmentation (computing) , mass spectrometry , ion , chromatography , stereochemistry , organic chemistry , computer science , operating system
Pyrrolizidine alkaloid (PA)–containing plants are widely distributed in the world. PAs are hepatotoxic, affecting livestock and humans. PA N ‐oxides are often present together with PAs in plants and also exhibit hepatotoxicity but with less potency. HPLC–MS is generally used to analyze PA‐containing herbs, although PA references are unavailable in most cases. However, to date, without reference standards, HPLC–MS methodology cannot distinguish PA N ‐oxides from PAs because they both produce the same characteristic ions in mass spectra. In the present study, the mass spectra of 10 PA N ‐oxides and the corresponding PAs were systemically investigated using HPLC–MS to define the characteristic mass fragment ions specific to PAs and PA N ‐oxides. Mass spectra of toxic retronecine‐type PA N ‐oxides exhibited two characteristic ion clusters at m / z 118–120 and 136–138. These ion clusters were produced by three unique fragmentation pathways of PA N ‐oxides and were not found in their corresponding PAs. Similarly, the nontoxic platynecine‐type PA N ‐oxides also fragmented via three similar pathways to form two characteristic ion clusters at m / z 120–122 and 138–140. Further application of using these characteristic ion clusters allowed successful and rapid identification of PAs and PA N ‐oxides in two PA‐containing herbal plants. Our results demonstrated, for the first time, that these characteristic ion clusters are unique determinants to discriminate PA N ‐oxides from PAs even without the availability of reference samples. Our findings provide a novel and specific method to differentiate PA N ‐oxides from PAs in PA‐containing natural products, which is crucial for the assessment of their intoxication. Copyright © 2012 John Wiley & Sons, Ltd.