Introduction: Lauraceae alkaloids are a structurally diverse class of plant specialised secondary metabolites that play an important role in modern pharmacotherapy, being useful as well as model compounds for the development of synthetic analogues. However, alkaloids characterisation is challenging due to low concentrations, the complexity of plant extracts, and long processes for accurate structural determinations. Objective: The use of high-performance thin layer chromatography coupled with desorption electrospray ionisation multistage mass spectrometry (HPTLC DESI-MS n) as a fast tool to identify alkaloids present in Ocotea spixiana extract and evaluate the extract's acaricide activity. Methods: Ocotea spixiana twigs were extracted by conventional liquid-liquid partitioning. HPTLC analysis of the ethyl acetate extract was performed to separate isobaric alkaloids prior to DESI-MS n analysis, performed from MS 3 up to MS 7. The extract's acaricide activity against Rhipicephalus microplus was evaluated by in vitro (larval immersion test) and in silico tests. Results: HPTLC-DESI-MS n analysis was performed to identify a total of 13 aporphine and four benzylisoquinoline-type alkaloids reported for the first time in O. spixiana. In vitro evaluation of the extract and the alkaloid boldine showed significant activity against R. microplus larvae. It was established in silico that boldine had important intermolecular interactions with R. microplus acetylcholinesterase enzyme. Conclusion: The present study demonstrated that HPTLC-DESI-MS n is a useful analytical tool to identify isoquinoline alkaloids in plant extracts. The acaricide activity of the O. spixiana ethyl acetate extract can be correlated to the presence of alkaloids. K E Y W O R D S acaricide activity, alkaloids, HPTLC-DESI-MS n , Ocotea spixiana 1 | INTRODUCTION Ocotea is an expressive genus of the Lauraceae family, occurring mainly in tropical and subtropical areas. 1 Species of this genus are known for producing a variety of secondary metabolites, with neolignans, aporphine and benzylisoquinoline-type alkaloids as the most representative classes. 2,3 A wide range of biological activities from Ocotea species has been described in the literature, including

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In the present study, five known γ‐lactones (majoranolide B – 1, majorenolide – 2, majorynolide – 3, lincomolide D – 4, and isolinderanolide E – 5), as well as a new one (perseanolide – 6), were isolated from Persea fulva and P. americana. All isolated compounds exhibited potential activity against trypomastigote forms of Trypanosoma cruzi, whereas compounds 2 (EC50 of 4.8 μM) and 6 (EC50 of 3.6 μM) displayed superior activity than the positive control benznidazole (EC50 of 16.4 μM), with selectivity index (SI) values of 17.8 and >55.6, respectively (benznidazole, SI>12.2). Molecular docking studies were performed for 1–6 against six T. cruzi molecular targets. Using this approach, we observed that, even though perseanolide (6) showed favorable docking to several studied targets, the results were especially promising for hypoxanthine phosphoribosyl transferase (PDB 1TC1). As PDB 1TC1 is associated to the transference of a monophosphorylated ribose from phosphoribosylpyrophosphate (PRPP) in the ribonucleotide synthesis pathway, this interaction may affect the survival of T. cruzi in mammalian cells. The data herein also indicate that possible intermolecular interactions between 6 and PDB 1TC1 derive from (i) hydrogen bonds in the α,β‐unsaturated‐γ‐lactone unity and (ii) hydrophobic interactions in the long‐chain alkyl group. Based on our results, perseanolide (6), reported for the first time in this work, can auspiciously contribute to future works regarding new trypanocidal agents.

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