Cataldi Tommaso R I, Lelario Filomena, Bufo Sabino A
Dipartimento di Chimica, Università degli Studi della Basilicata, Via N. Sauro, 85100 Potenza, Italy.
Rapid Commun Mass Spectrom. 2005;19(21):3103-10. doi: 10.1002/rcm.2176.
Steroidal glycoalkaloids (SGAs) extracted from tomato leaves and berries (Lycopersicon esculentum Mill.) were separated and identified using optimized reversed-phase liquid chromatography with electrospray ionization (ESI) and ion trap mass spectrometry (ITMS). The ESI source polarity and chromatographic conditions were evaluated. The ESI spectra contain valuable information, which includes the mass of SGAs, the mass of the aglycones, and several characteristic fragment ions. Cleavage at the interglycosidic bonds proximal to the aglycones is the most prominent process in the ESI process. A protonated molecule, [M+H]+, accompanied by a mixed adduct ion, [M+H+Na]2+, was observed for alpha-tomatine (i.e., m/z 1034.7 and 528.9) and dehydrotomatine (i.e., m/z 1032.6 and 527.9) in positive ion mode spectra. The structures of these tomato glycoalkaloids were confirmed using tandem mass spectrometry. The identification of a new alpha-tomatine isomer glycoalkaloid, named filotomatine (MW 1033), which shares a common tetrasaccharide structure (i.e., lycotretraose) with alpha-tomatine and dehydrotomatine, and soladulcidine as an aglycone, is described for the first time. It occurs in significant amounts in the extracts of wild tomato foliage. Multistage mass spectrometry both of the protonated molecules and of the doubly charged ions was used for detailed structural elucidation of SGAs. Key fragmentations and regularities in fragmentation pathways are described and the fragmentation mechanisms involved are proposed.
从番茄叶和果实（番茄）中提取的甾体糖生物碱（SGAs），通过优化的反相液相色谱与电喷雾电离（ESI）和离子阱质谱（ITMS）进行分离和鉴定。对ESI源极性和色谱条件进行了评估。ESI谱包含有价值的信息，包括SGAs的质量、苷元的质量以及几个特征性碎片离子。在苷元附近的糖苷键处断裂是ESI过程中最显著的过程。在正离子模式谱中，观察到α-番茄碱（即m/z 1034.7和528.9）和脱氢番茄碱（即m/z 1032.6和527.9）的质子化分子[M+H]+以及混合加合离子[M+H+Na]2+。这些番茄糖生物碱的结构通过串联质谱得到确证。首次描述了一种新的α-番茄碱异构体糖生物碱，命名为菲洛番茄碱（分子量1033），它与α-番茄碱和脱氢番茄碱具有共同的四糖结构（即番茄四糖），苷元为澳洲茄碱，在野生番茄叶提取物中大量存在。对质子化分子和双电荷离子均采用多级质谱对SGAs进行详细的结构解析。描述了关键的碎片化过程和碎片化途径中的规律，并提出了所涉及的碎片化机制。
