title: An integrated strategy for the systematic characterization and discovery of new indole alkaloids from Uncaria rhynchophylla by UHPLC/DAD/LTQ-Orbitrap-MS.
abstract: The exploration of new chemical entities from herbal medicines may provide candidates for the in silico screening of drug leads. However, this significant work is hindered by the presence of multiple classes of plant metabolites and many re-discovered structures. This study presents an integrated strategy that uses ultrahigh-performance liquid chromatography/linear ion-trap quadrupole/Orbitrap mass spectrometry (UHPLC/LTQ-Orbitrap-MS) coupled with in-house library data for the systematic characterization and discovery of new potentially bioactive molecules. Exploration of the indole alkaloids from Uncaria rhynchophylla (UR) is presented as a model study. Initially, the primary characterization of alkaloids was achieved using mass defect filtering and neutral loss filtering. Subsequently, phytochemical isolation obtained 14 alkaloid compounds as reference standards, including a new one identified as 16,17-dihydro-O-demethylhirsuteine by NMR analyses. The direct-infusion fragmentation behaviors of these isolated alkaloids were studied to provide diagnostic structural information facilitating the rapid differentiation and characterization of four different alkaloid subtypes. Ultimately, after combining the experimental results with a survey of an in-house library containing 129 alkaloids isolated from the Uncaria genus, a total of 92 alkaloids (60 free alkaloids and 32 alkaloid O-glycosides) were identified or tentatively characterized, 56 of which are potential new alkaloids for the Uncaria genus. Hydroxylation on ring A, broad variations in the C-15 side chain, new N-oxides, and numerous O-glycosides, represent the novel features of the newly discovered indole alkaloid structures. These results greatly expand our knowledge of UR chemistry and are useful for the computational screening of potentially bioactive molecules from indole alkaloids. Graphical Abstract A four-step integrated strategy for the systematic characterization and efficient discovery of new indole alkaloids from Uncaria rhynchophylla.
authors.affiliation: Shanghai Research Center for Modernization of Traditional Chinese Medicine, National Engineering Laboratory for TCM Standardization Technology, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Haike Road 501, Shanghai, 201203, China.
authors.forename: Huiqin
authors.initials: H
authors.lastname: Pan
authors.forename: Wenzhi
authors.initials: W
authors.lastname: Yang
authors.forename: Yibei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Min
authors.initials: M
authors.lastname: Yang
authors.forename: Ruihong
authors.initials: R
authors.lastname: Feng
authors.forename: Wanying
authors.initials: W
authors.lastname: Wu
authors.forename: Dean
authors.initials: D
authors.lastname: Guo
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006027:Glycosides / Q000032:analysis; D026121:Indole Alkaloids / Q000032:analysis*; D013058:Mass Spectrometry / Q000379:methods; D010936:Plant Extracts / Q000737:chemistry*; D018547:Plant Stems / Q000737:chemistry; D032070:Uncaria / Q000737:chemistry*
chemical_list: D006027:Glycosides; D026121:Indole Alkaloids; D010936:Plant Extracts