Estudo fitoquímico das folhas de Pseudoxandra leiophylla (Annonaceae) e investigação do seu efeito citotóxico

Abstract

Pseudoxandra leiophylla (Diels) is a species belonging to the Annonaceae family, native to the Amazonian territory, occurring in Venezuela, Colombia and Brazil. Its synonymy is Pseudoxandra coriacea R. E. Fr. According to the literature, there are no records of chemical and pharmacological studies on this species. In this work, the phytochemical study and the "in vitro" cytotoxicity investigation of the extracts, fractions (neutral and alkaloidic) and isolated compounds from P. leiophylla leaves. The study of the leaves resulted in the isolation of six substances belonging to the class of alkaloids, terpenes and lignoids. Classical chromatographic techniques such as column chromatography and preparative thin-layer chromatography were used to isolate the chemical constituents, and spectroscopic (1H and 13C 1D/2D nuclear magnetic resonance) and spectrometric (mass spectrometry) techniques were used. The alkaloids belong to the aporphin and oxoaporphin classes and were identified as liriodenin and asimilobin, respectively. The terpenes are the triterpenes heynic acid, the mix of brein and manniladiol, and the sesquiterpene lactone loliolide, as well as the tetrahydrofuran lignan identified as grandisin. All these compounds are described for the first time in the species. The extracts (hexanic and methanolic), fractions (neutral and alkaloidic), as well as the substances isolated from P. leiophylla leaves were submitted to cytotoxic activity assays against tumor cell lines using the Alamar Blue assay. The results of the cytotoxicity assay of the extracts and fractions showed potential cytotoxic activity against tumor cell lines with IC50 values below 50 μg.mL-1, where among the extracts evaluated, the hexanolic extract was the most active with IC50 values equal to 28.50 and 13.12 μg.mL-1 against human colon carcinoma (HCT116) and human hepatocellular carcinoma (HepG2) cells, respectively. The methanolic extract was active only against the tumor cell type HepG2 with CI50 value equal to 12.85 μg.mL-1. On the other hand, the neutral and alkaloidic fractions showed IC50 values equal to 42.47 and 8.32 μg.mL-1, and 31.86 and 9.85 μg.mL-1 for HCT116 and HepG2, respectively, improving the activity of the methanolic extract with acid-base treatment. However, the results are considered close with both active fractions having probable promising substances. For the isolated substances only the brein and manniladiol mixture showed some cytotoxic activity with a IC50 value of 8.32 μg.mL-1 against B16-F10 tumor cells. The results contributed to the chemical and pharmacological knowledge of Annonaceae species from Amazonas, particularly for species of the gender Pseudoxandra.