Characterization and Identification of Prenylated Flavonoids from Artocarpus heterophyllus Lam. Roots by Quadrupole Time-Of-Flight and Linear Trap Quadrupole Orbitrap Mass Spectrometry

In this study, a combination of quadrupole time-of-flight mass spectrometry (Q-TOF-MS) and linear trap quadrupole orbitrap mass spectrometry (LTQ-Orbitrap-MS) was performed to investigate the fragmentation behaviors of prenylated flavonoids (PFs) from Artocarpus plants. Fifteen PFs were selected as the model molecules and divided into five types (groups A–E) according to their structural characteristics in terms of the position and existing form of prenyl substitution in the flavone skeleton. The LTQ-Orbitrap-MS(n) spectra of the [M − H](−) ions for these compounds provided a wealth of structural information on the five different types of compounds. The main fragmentation pathways of group A were the ortho effect and retro Diels–Alder (RDA), and common losses of C(4)H(10), CO, and CO(2). The compounds in group B easily lose C(6)H(12), forming a stable structure of a 1,4-dienyl group, unlike those in group A. The fragmentation pathway for group C is characterized by obvious (1,4)A(−), (1,4)B(−) cracking of the C ring. The diagnostic fragmentation for group D is obvious RDA cracking of the C ring and the successive loss of CH(3) and H(2)O in the LTQ-Orbitrap-MS(n) spectra. Fragmentation with successive loss of CO or CO(2), ·CH(3), and CH(4) in the LTQ-Orbitrap-MS(n) spectra formed the characteristics of group E. The summarized fragmentation rules were successfully exploited to identify PFs from Artocarpus heterophyllus, a well-known Artocarpus plant, which led to the identification of a total of 47 PFs in this plant.