Cytotoxic Activity of Baccharis species

Cancer has become an alarming problem worldwide, with a growing number of cases in recent decades. According to WHO (2018), approximately 14 million new cases of cancer are registered annually. The available pharmacological treatments are not specific and induce serious adverse effects and new therapeutic options are therefore demanded. Most approved antineoplastic drugs have been developed, directly or indirectly, from natural products. In this context, the objective of the present work was to assay the cytotoxic activity of Baccharis species and to undertake dereplication of selected extracts by UPLC-MS/MS.
Vegetal materials of 19 Baccharis species were collected in Parque Nacional do Caparaó and Serra da Calçada (MG). The extracts were obtained by maceration with ethanol 96° GL of the dried plant drugs. Subsequently, the cytotoxicity of the extracts was evaluated against non-small cell lung cancer (A549), liver hepatocellular carcinoma (HepG2) and prostate cancer cells (DU145) by the sulforhodamine B assay, using different concentrations (0.78 to 100 µg/mL). Paclitaxel (1 μM) was used as positive control. The extract of Baccharis megapotamica leaves showed promising cytotoxic activity, with IC50 values of 2.77; 1.40 and 3.04 μg/mL against A549, HepG2 and DU145 cells, respectively.
A bulk amount of extract was prepared by percolation of B. megapotamica leaves with ethanol 96ºGL. Portions of this extract were suspended in water and fractionated by partition between immiscible solvents, sequentially with n-hexane, dichloromethane and ethyl acetate. The resulting fractions were submitted to cytotoxicity assay, employing the same cell lines. The hexane fraction showed IC50 values of 2.20 μg/mL for HepG2 cells and < 0.78 μg/mL for A549 and DU145 cells; the dichloromethane fraction presented IC50 values lower than 0.78 μg/mL for all assayed cells lines, whereas the ethyl acetate fraction showed IC50 values of 6.30; 10.0 and 3.93 μg/mL, respectively for A549, HepG2 and DU145 cells.
B. megapotamica extract and fractions thereof were subjected to analysis by UPLC-ESI-MS/MS on RP-18 column and gradient elution of acidified ACN: H2O (0.1% v/v HCOOH). Dereplication of the extract and fractions demonstrated the putative presence of flavonoids and phenolic compounds such as quercetin, caffeoylquinic acids and dicaffeoylquinic acids. The obtained data also suggested the presence of macrocyclic trichothecenes, already reported for the specie. In conclusion, B. megapotamica extract and fractions have potential cytotoxic activity and are present flavonoids and phenolic acids as constituents.