Integrative Approach Based on Leaf Spray Mass Spectrometry, HPLC‑DAD‑MS/MS, and NMR for Comprehensive Characterization of Isoquinoline-Derived Alkaloids in Leaves of Onychopetalum amazonicum R. E. Fr.

Abstract

Onychopetalum is an Amazonian botanical genus close-related with Bocageopsis and Unonopsis, whose species are used in traditional medicine. Although these genera are widely investigated from the phytochemical viewpoint, the knowledge about Onychopetalum remains almost unexplored. In order to perform a comprehensive characterization of isoquinoline-derived alkaloids from Onychopetalum amazonicum, an integrative approach based on the alkaloid profile analysis by leaf spray mass spectrometry (LS-MS), followed by a robust dereplication through highperformance liquid chromatography coupled with diode array detector and atmospheric pressure chemical ionization tandem mass spectrometry, (HPLC-DAD-APCI-MS/MS) and nuclear magnetic resonance (NMR) analysis was adopted. LS-MS allowed the tentative identification of reticuline, norjuziphine, nornuciferine, O-methylisopiline, nuciferine, N-methyl-O-methylisopiline, anonaine, and N-methylanonaine. HPLC-DAD-MS/MS analysis supported the tentative identification of N-methylasimilobine, asimilobine, norushinsunine, N-methylisopiline, isopiline, liriodenine, and lysicamine. Moreover, the integration of MS and NMR data allowed the additional identification of stepholidine and isocorypalmine. The applied integrative approach proposed herein enabled a comprehensive analysis of the alkaloid content from the O. amazonicum, showing to be a useful strategy for the dereplication of isoquinoline-derived alkaloids.

Molecular networking‐based dereplication of strictosidine‐derived monoterpene indole alkaloids from the curare ingredient Strychnos peckii

“…In order to confirm the presence of MIAs in the leaves of S. peckii , and to establish the skeleton arrangements, LS‐MS and LS‐MS/MS experiments were carried out to fingerprint the samples. This approach was adopted since this is a rapid and low‐cost sampling method that provides real‐time information, being useful, in the positive ion mode, mainly for the screening of alkaloids . Thus, the positive LS‐MS spectrum (Figure A) displayed a base peak at m / z 531, along with other less intense ions, including an ion at m / z 571.…”

“…Although the loss of 162 Da (glucose) has been successfully applied as a neutral loss filtering to identify MIAs, this loss is common to other classes, such as triterpene saponins and flavonoid glucosides . The loss of 17 Da (NH 3 ) is also not a structurally significant neutral loss for MIAs, although it is restricted to alkaloids . However, due to the historic occurrence of MIAs within Strychnos , both losses could be used to screen for specific MIAs.…”

“…The MS and MS/MS leaf spray measurements were performed with a home‐made ion source and a TSQ Quantum Access triple quadrupole mass spectrometer (Thermo Fisher, San Jose, CA, USA) according to a previously reported methodology . In brief, dried leaves were cut into triangle‐shaped pieces (base and height of 10 mm each) and held by a metal clip at a distance of 10 mm from the mass spectrometer inlet.…”

Green Extraction of Alkaloids and Polyphenols from Peumus boldus Leaves with Natural Deep Eutectic Solvents and Profiling by HPLC-PDA-IT-MS/MS and HPLC-QTOF-MS/MS

“…Fragments ions at m/z 264 and m/z 248.1 correspond to the consecutive loss of two methyl groups. According to these data, the identity of peak 21 is assigned to isocorydine [36]. For the compound corresponding to peak 27 in positive ionization mode, the molecular formula of ion at m/z 327.14735 was predicted as C 19 H 21 NO 4 .…”

“…In HPLC-PDA-IT-MS/MS analysis, peak 15 showed a molecular ion at m/z 330 [M + H] + and in MS/MS a prominent product ion at m/z 192 [M + H-138] + , which is consistent with the loss of C ring with methoxyl and hydroxyl groups previous to a putative loss of 31 Da from CH 3 NH 2 (very low abundance of fragment at m/z 299). In addition, fragment ion at m/z 192 is a diagnostic ion used to confirm the presence of a methoxyl and hydroxyl groups at the A ring in benzylisoquinoline alkaloids [31,35,36]. According with MS data, peak 15 is reticuline.…”