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Strychnos peckii (Loganiaceae) is an important active ingredient in curare poisons in the Amazon rainforest. Although previous studies have identified this species as a promising source of monoterpene indole alkaloids (MIAs), knowledge about other natural products is still scarce. Thus, to detect and guide the isolation of unprecedented bioactive compounds from the leaves of S. peckii, an untargeted high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) analysis was performed with the leaf aqueous extract. The HPLCMS analysis allowed the detection of eleven compounds, including the alkaloids harman-3-carboxylic acid (5) and N,ß-glucopyranosyl vincosamide (6), and the flavonoids quercetin 3-O-rhamnopyranoside (9) and kaempferol 3-Orhamnopyranoside (10), all not previously reported in the Loganiaceae family. These compounds, along with strictosidine (3), 5-carboxystrictosidine (7), and desoxycordifoline (8) were isolated through modern chromatographic techniques and determined by using NMR spectroscopy in combination with MS. Overall, the untargeted HPLC-MS analysis proved to be a simple and effective approach to guide the isolation of substances not yet identified from S. peckii. [ABSTRACT FROM AUTHOR]

Rationale: Monoterpene indole alkaloids (MIAs) are a large group of biologically active compounds produced by hundreds of plant species in numerous plant families, such as Apocynaceae, Loganiaceae and Rubiaceae. Although this diversity is biosynthetically intermediated by strictosidine, there are no works focused on the fragmentation patterns under collision-induced dissociation of strictosidine-derived alkaloids., Methods: Initially, the alkaloid fingerprint of Strychnos peckii was established using 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 out to focus on the patterns of neutral losses in 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: LS-MS/MS allowed the tentative identification of strictosidine-derived alkaloids in the leaves of S. peckii, showing useful neutral losses for the dereplication of strictosidine analogues by HPLC/MS/MS experiments. The use of MN combined with manual interpretation of the fragmentation patterns highlighted characteristic fragmentation pathways, and allowed the tentative identification of strictosidine, desoxycordifoline, strictosidinic acid, 10-hydroxystrictosidine, 5-carboxystrictosidine, lyaloside, 3,4-dehydrostrictosidine and strictosidine lactam., Conclusions: The use of MN combined with the analysis of the fragmentation patterns proved to be a useful strategy for the dereplication of strictosidine-derived MIAs from S. peckii, highlighting known and unprecedented structures, as well as useful diagnostic product ions. Therefore, this workflow is an effective approach for the characterization of strictosidine-type alkaloids in future dereplication works., (© 2019 John Wiley & Sons, Ltd.)