Investigação do perfil de alcaloides de espécies de Aspidosperma spp por LC-MS

Abstract

Aspidosperma genus is known for its secondary metabolites, among which we can highlight the indolic alkaloids, a class of compounds widely known by the pharmaceutical industry due to their various functions in the biological system. Thus, this study's objective is to contribute to the knowledge about the alkaloid profile present in the bark of A. desmanthum, A. marcgravianum, and A. nitidum through liquid chromatography coupled to mass spectrometry (LC-MS) and to evaluate the antioxidant potential, the inhibition of acetylcholinesterase enzyme, cytotoxic activity and to assess the antimicrobial activity through in vitro assays. The barks of Aspidosperma species were submitted to methanol extraction, followed by an acidbase fractionation, and the aqueous extract was also prepared. The samples obtained were analyzed by LC-MS, and the GNPS (Global Natural Products Social Networking) platform was used to construct a molecular network, where it was possible to identify nine indolic alkaloids, which were shared among the species. Among the identified alkaloids, ioimbine, reserpiline, and ajmalicine stand out because they are precursor alkaloids of other alkaloids of great relevance. Through the evaluation of the antioxidant activity, it is possible to observe the importance of performing more than one method to determine the antioxidant activity of a sample. In this study, for example, the samples tested showed antioxidant activity by the Ferric Reduction Antioxidant Power (FRAP) and had lower efficiency in the DPPH radical scavenging assay. The inhibitory activity of the acetylcholinesterase assay showed the fraction from A. marcgravianum with the highest percentage of inhibition, 72.32%, but the sample of the methanolic extract showed higher effectiveness, CI50 3.38. The alkaloidic fractions' cytotoxicity was analyzed using the MTT method in normal cells and tumor cells (HL60 cells). However, the tested fractions showed no selectivity against the evaluated cells. The metabolic extract of A. marcgravianum obtained 3.12 of minimum inhibitory concentration (MIC per µg/mL) against S. aureus and was the only sample reactive against P. aeruginosa with MIC of 50 µg/mL. The species studied has significant potential for the isolation of indolic alkaloids and represents an option for investment in future studies.