Constituintes químicos e investigação do efeito citotóxico das cascas e folhas de Duguetia pycnastera (Annonaceae)

Abstract

Duguetia pycnastera is a species of the family Annonaceae popularly known as “envira-preta” with distribution in northern South America. In Brazil it is quite common in Amazonas and Amapá. Based on literature data, this species has only two photochemical studies, with the volatile components of essential oil (published data) and the isolation of alkaloids (unpublished data) being reported. Thus, in the present work, a phytochemical study and investigation of the in vitro cytotoxicity activity of crude extracts, fractions and substances isolated from the bark of D. pycnastera stem was carried out. The phytochemical study of the shells resulted in the isolation and characterization of seven substances, five belonging to the class of alkaloids and two of benzene character (phenylpropanoids). Classical chromatographic techniques (CC, CCDA and CCDP) were used for the isolation of chemical constituents, while spectroscopic (1H and 13C 1D / 2D NMR) and spectrometric (EM and CG-EM) techniques were used for identification. The study of the profile by the EM technique with leaf spray source using fragmentation keys allowed to identify possible skeletons of alkaloids present in the alkaloid fraction. Seven (7) isoquinoline alkaloids (N-oxyiguaterine, nornuciferidine, lysicamine, O-methylmoschatoline and reticulin) were isolated. The identified phenylpropanoids belong to the asarone class (1-allyl-2,4,5-trimethoxybenzene and 2,4,5-trimethoxy-styrene). All alkaloids identified in this work are reported in the genus, however, they are unprecedented in the species, with oxoaporphine alkaloids being the most common. Among the extracts and fractions of the shells submitted to the in vitro cytotoxic activity test, the alkaloid fraction from the methanolic extract showed greater activity against the tumor cell lines evaluated, with IC50 values equal to 14.09 μg.mL-1 for MCF -7 and 11.58 μg.mL-1 for HepG2. Among the isolated and evaluated alkaloids, lysicamine and O-methylmoschatoline were the substances that present the best cytotoxic results, in particular against the cell lines HepG2 and HL-60 (IC50 29.08 and 24.68 µmol.L-1, respectively) for lysicamine and for O-methylmoschatoline it showed promising cytotoxic activity for the HL-60 cell (34.85 µmol.L-1). Through the GC-MS analysis of the essential oil, 24 constituents were identified, with sesquiterpenes α-gurjunene (26.83%), bicyclogermacrene (24.90%), germacrene D (15.35%), standing out as major constituents. ) and spatulenol (12.97%). The results obtained in this study confirm the chemical and cytotoxic potential of Brazilian Annonaceaes species, in particular, species occurring in Amazonas. Thus, it is worth emphasizing the importance of continuing studies of this species in future projects in the search for substances with cytotoxic properties.