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

Introduction: The genus Strychnos is an important source of monoterpene indole alkaloids (MIAs), which are an important class of secondary plant metabolites found in hundreds of species among the Alangiaceae, Apocynaceae, Gelsemiaceae, Icacinaceae, Loganiaceae, Nyssaceae, and Rubiaceae plant families (Brown et al., 2015; Silva et al., 2005). Several plants containing MIAs are used in the traditional medicine, or in other ethnobotanical practices, such as hunting (e.g. S. peckii), fishing and for defense purposes (Philippe et al., 2004; QuentinLeclercq et al., 1990). Although this chemical diversity is biosynthetic intermediated by strictosidine, there are no works focused on fragmentation pattern analysis of strictosidine-type alkaloids. Material and methods: Initially, the alkaloid fingerprint of S. peckii was established by leaf spray with tandem mass spectrometry (LS-MS/MS). Then, high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) analyses were carried to focus on the neutral losses’ patterns under product ion scan experiments with the leaf aqueous extract. Finally, the product ion spectra from a set of presumable strictosidine-type derivatives were analyzed and organized via molecular networking (MN), and dereplicated by manual interpretation of MS/MS spectra. Results e Discussion: The LS-MS analysis allowed the tentative identification of the (MIAs) strictosidine and desoxycordifoline in the leaves of S. peckii, and showed useful neutral losses for the recognition of their analogues by HPLC-MS/MS experiments. The use of MN combined with manual interpretation of the MS/MS spectra highlighted key fragmentations for MIAs and allowed the tentative identification of the strictosidinic acid, 10-hydroxy strictosidine, 5α-carboxystrictosidine, lyaloside, 3,4-dehydrostrictosidine, and strictosidine lactam, besides suggest the presence of unprecedented structures. The proposed showed to be a useful strategy for the recognition of strictosidine-type MIAs in complex matrices, highlighting known and unprecedented structures, and diagnostic product ions. Therefore, this can be an effective approach for characterizing strictosidine-type alkaloids in future dereplication works.