Cytotoxic biomonitored study of Euphorbia umbellata (Pax) Bruyns

Ethnopharmacological relevance: Euphorbia umbellata latex (sap) has normally been used in folk medicine in southern Brazil to treat different types of cancers.

Aim of study: To carry out a biomonitored investigation of partitioned latex using in vitro assay, to identify the main mechanisms related with the action of the most active fraction as well as to develop a phytochemical study with this material.

Materials and methods: Biological screening was performed with hexane, chloroform, ethyl acetate and methanol fractions from the latex of E. umbellata using MTT, trypan blue, and neutral red assays to determine the cytotoxicity against HRT-18, HeLa and Jurkat cells and flow cytometry, DNA quantification, acridine orange and Hoechst 33342 staining to investigate mechanisms of action for the hexane extract. The phytochemical study of the hexane fraction was performed by chromatographic procedures and the substances were identified by NMR analysis. The isolated terpenes were evaluated using MTT to determine the cytotoxicity against Jurkat cells.

Results: All the fractions presented concentration and time dependent cytotoxicity. The hexane fraction showed the highest cytotoxicity; whereas the Jurkat cell was the lineage with the highest sensitivity (IC50 1.87µg/mL). Fragmentation of DNA and apoptosis are two mechanisms related with the toxicity of hexane fraction. The hexane fraction arrested the cell cycle in the G0/G1 phase, and the selectivity index was 4.30. Phytochemical study of the hexane fraction led to isolation of euphol (main compound) and germanicol acetate. Both substances demonstrated some slight cytotoxic activity against Jurkat cells after 72h; however the activity was minimal compared to vincristine (anticancer standard drug).

Conclusion: The current research proves that the fractions of the latex from E. umbellata have a cytotoxic effect against three different cancer cells lines. The hexane fraction showed high in vitro cytotoxic effects against Jurkat cells demonstrating that the effect may be due to non-polar constituents. The two isolated terpenes (euphol and germanicol acetate) showed poor cytotoxic activity indicating that the anticancer properties of the extract may be caused by other substances present in the hexane fraction.