Contribuição ao estudo fitoquímico das folhas de Annona neoinsignis H. Rainer (Annonaceae) e investigação das suas propriedades citotóxicas

Abstract

The genus Annona L., with approximately 166 species, is part of the Annonaceae family and is regarded as the most significant within this family due to the economic value of its edible fruits and the medicinal properties of several species. Despite being well-studied, there are still some species that remain unexplored from both chemical and biological perspectives. One such species is Annona neoinsignis H. Rainer (synonym: Rollinia insignis R. E. Fries), which produces yellow fruits when ripe. These fruits have a very rough skin, contain several seeds, and feature a pleasantly flavored pulp. This study focused on the phytochemical examination of A. neoinsignis leaves, particularly evaluating the in vitro cytotoxicity of extracts, fractions, essential oil, and isolated compounds. The analysis of the alkaloid fraction resulted in the isolation and characterization of six alkaloids that contain an isoquinoline skeleton, along with one lactone. For the isolation of these compounds, classical chromatographic techniques such as column chromatography (CC) and thin-layer chromatography (TLC) were utilized. Structural identification was conducted using spectroscopic techniques (1D/2D 1H and 13C NMR) and spectrometric techniques (MS). The essential oil was extracted from the leaves during six different time periods using hydrodistillation, and its chemical constituents were identified and quantified using gas chromatography with flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The isolated and identified alkaloids belong to various classes: oxoaporphines (liriodenine and lysicamine), aporphines (nornuciferine, anonaine, and asimilobine), and tetrahydroprotoberberines (stepholidine), along with a lactone (loliolide). The essential oil study showed that the major compound for the June/23 period was germacrene D (24.11%), for October/24 was (E)-caryophyllene (26.38%), and for July/24, January/25, April/25, and July/25, the major compound was β-elemene, representing 29.61%, 24.61%, 30.0%, and 27.8%, respectively. The in vitro cytotoxic evaluation of the June/23 essential oil showed promising cytotoxicity against HCT116 and HepG2 tumor cells with IC50 values of 28.71 and 27.90 μg/mL, respectively, while showing no cytotoxicity against normal cells. Combined with the in vitro and in vivo studies of the July/24 oil, it was found that the latter was capable of inducing cell death in liver cancer cells. Furthermore, three alkaloids demonstrated promising cytotoxic activity. Therefore, the results obtained are in agreement with those reported in the literature for several species of the Annona genus and contribute to the knowledge of Annonaceae species from the Amazon. Additionally, all the results reported here are described for the first time for this species, indicating yet another Annonaceae species as a promising source of cytotoxic substances against human tumor cell lines.