Systematic Detection and Identification of Bioactive Ingredients from Citrus aurantium L. var. amara Using HPLC-Q-TOF-MS Combined with a Screening Method.

Bitter orange, Citrus aurantium L. var. amara (CAVA), is an important crop and its flowers and fruits are widely used in China as a food spice, as well as in traditional Chinese medicine, due to its health-promoting properties. The secondary metabolites that are present in plant-derived foods or medicines are, in part, responsible for the health benefits and desirable flavor profiles. Nevertheless, detailed information about the bioactive ingredients in CAVA is scarce. Therefore, this study was aimed at exploring the phytochemicals of CAVA by high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). Here, a systematic screening method combined with HPLC-Q-TOF-MS was presented. This technique was used to systematically screen metabolites, primarily from the complex matrix of CAVA, and to identify these compounds by their exact masses, characteristic fragment ions, and fragmentation behaviors. A total of 295 metabolites were screened by the screening method and 89 phytochemicals were identified in the flowers, fruits, roots, leaves, and branches of CAVA. For the first time, 69 phytochemicals (flavonoids, alkaloids, terpenoids, etc.) were reported from CAVA. The results highlight the importance of CAVA as a source of secondary metabolites in the food, medicine, and nutraceutical industries.

Investigation of fragmentation behaviours of isoquinoline alkaloids by mass spectrometry combined with computational chemistry.

Isoquinoline alkaloids, which are one of the most important types of alkaloids, are extensively distributed in herbal medicines. However, systematic and comprehensive investigations of the fragmentation behaviours of isoquinoline alkaloids have rarely been reported. Therefore, the goal of the present study is to simultaneously investigate the collision-induced dissociation patterns and the corresponding mechanism of isoquinoline alkaloids by mass spectrometry (MS) combined with computations. Nineteen types of isoquinoline alkaloids (66 compounds) were used as references to identify the characteristic fragmentation behaviours by quadrupole time-of-flight mass spectrometry (Q-TOF/MS) in positive electrospray ionization (ESI) mode. These types of isoquinoline alkaloids were divided into three categories primarily by the characteristic [M-NHR1R2]+ (R1 and R2 represent the substituent groups of the N-atom) fragment ions. High- and low-abundance [M-NHR1R2]+ ions were observed respectively for type I (1-13) and type II (14-29) alkaloids, respectively; however, the characteristic fragments were not detected for type III alkaloids (30-66) because of the existence of a p-π conjugated system. Each type of alkaloid was further classified by its characteristic fragmentation patterns and fragment ions. In addition, isoquinoline alkaloid with vicinal methoxy and hydroxy, vicinal methoxy, methylenedioxy, methoxy, and quaternary N-methyl groups could form the characteristic fragments by the loss of CH3OH, CH4, CH2O or CO, CH3 and CO, and CH3 moieties, respectively. The mechanisms of some interesting fragmentation behaviours, such as the formation of [M-NH3]+ and [M-CH3]+ fragment ions, were further demonstrated by computational chemistry. These characteristic fragmentation behaviours and fragment ions of isoquinoline alkaloids provide a solid foundation for the rapid and high-efficiency structural elucidation of similar metabolites in plant-derived medicines.

Systematic identification metabolites of Hemerocallis citrina Borani by high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry combined with a screening method.

Hemerocallis citrina Borani is an important crop and its flower buds are widely consumed in East Asian areas as a vegetable, as well as in traditional Chinese medicine, due to its health-promoting properties. Metabolites present in plant-derived foods or medicines are in part responsible for their desirable flavor profiles and health benefits. Nevertheless, detailed information about these compounds in H. citrina is scarce. Therefore, this study aimed to investigate the metabolites by high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). In this study, a total of 144 compounds, including 14 amides, 25 polyphenols, 44 flavonols, 35 anthraquinones, 15 naphthols, and 11 other components, were detected by the established screening method and were identified by their precise m/z values, characteristic tandem mass spectrometry (MS/MS) data and fragmentation pathways of references, 111 of which were reported in this plant for the first time. The distribution of identified ingredients in different parts of H. citrina was determined. Interestingly, colchicine, which had been reported as a toxic compound in the fresh flower buds in previous studies and various news reports, was not found. This work marks the first comprehensive study of metabolites from commercial flower buds and different parts of H. citrina.