Efeito citotóxico do látex de Euphorbia umbellata (Pax) Bruyns (Euphorbiaceae) para modelo de melanoma murino

Abstract

Euphorbia umbellata (Pax) Bruyns is popularly known as "janauba" and its latex is empirically used for the treatment of several diseases, including cancer. So, the aim of this work was to evaluate the in vitro and in vivo cytotoxic activity of compounds present in E. umbellata latex, based on its use and ethno pharmacological indication,and correlate the results to the chemical composition of this plant. For this, the latex was collected and fractionated in Soxhlet extractor and 8 extracts (samples) were obtained. The extracts were used in the cytotoxicity assays (MTT and neutral red) against the B16F10 (murine melanoma) cell lines. The results were used to calculate the IC50 and, based on these; the selectivity index (IS) was determinate. For in vivo assays, 36 male C57BL/6 mice were used and B16F10 cells were inoculated for tumor formation and subsequently these animals were treated with dichloromethane subfraction at concentrations of 1 mg/ml and 10 mg/ml per 15 days. In vitro results were pertinent for latex (IC50 = 0.69 ± 0.12 μg/ml, with IS = 0.6 by MTT assay; and IC50 = 0.02 ± 0.004 μg/ml, with IS = 6.3 by neutral red assay) and for the hexane fraction (IC50 = 24.44 ± 2.30 μg/ml, with IS = 0.8, by MTT assay and IC50 = 21.30 ± 16.60 μg/ml, with IS = 1.1 by neutral red assay); for the petroleum ether (IC50 = 5.99 ± 0.23 μg/ml with IS = 3.98 by MTT) and dichloromethane (IC50 = 16.20 ± 7.33 μg/ml with IS = 0.30 by MTT) subfractions the results were promising. The spectrophotometric analysis of the fractions allowed determining that the dichloromethane subfraction has the highest amount of total terpenes expressed in eufol. In addition, the analysis of fractions by the LC-MS/MS technique allowed determining that the chloroform and ethyl acetate fractions and the ethanol subfraction presented a large amount of phorbol esters in their compositions. Regarding the in vivo results, for the experiment carried out in this work, it was found that the dichloromethane subfraction did not show a significant difference in the tumor volume in the tested concentrations, compared to the negative control. It is concluded that E. umbellata latex has in vitro cytotoxic potential compared to the B16F10 cell, a result that was not confirmed in the in vivo experiments in this work; it can still be inferred that this action may be related to the presence of terpenes in the plant matrix.