Investigação fitoquímica das folhas de Strychnos peckii B. L. Rob. (Loganiaceae)

Abstract

The genus Strychnos stands out in the Amazon region due to its use in traditional medicine and other ethnobotanical practices such as hunting (curare) and fishing. Although some species of this genus have been investigated from the phytochemical point of view, many others are practically unexplored, such as S. peckii, which are recognized as curare ingredient. In this context, the present work sought to investigate the phytochemical content of S. peckii leaves. Initially, the leaves were subjected to leaf spray mass spectrometry (LS-MS) analysis, being their respective aqueous extracts (SPIF) investigated by high performance liquid chromatography-coupled to mass spectrometry (HPLC-MS) combined with data organization by molecular network (MN) and/or manual interpretation of MS/MS spectra. Finally, the aqueous extracts containing desired or supposedly unpublished molecules were fractionated on semi-preparative HPLC. The LS-MS analysis allowed the tentative identification of the monoterpene indole alkaloids (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, 5-carboxystrictosidine, lyaloside, 3,4-dehydro-strictosidine, and strictosidine lactam from SPIF, besides suggesting the presence of unpublished molecules in this sample. The SPIF fractionation resulted in the isolation of the alkaloids desoxycordifoline, 5-carboxystrictosidine, N,β-glucopyranosil vincosamide, strictosidine and the harman-3-carboxylic acid and the flavonoids kaempferol-3-O-α-rhamnoside and quecetin-3-O-α-rhamnoside. The proposed approach was useful to characterize the phytochemical content of S. peckii leaves, qualifying this species as a promising source of bioactive substances and contributing to the chemical knowledge of the genus Strychnos.