Cytotoxic mechanism of Baccharis milleflora (Less.) DC. essential oil

The aim of this study was to investigate the cytotoxic activity of the essential oil from cladodes of Bacharis milleflora in relation to Jurkat, Raji and HL-60 cells, as well as exploring the cell mechanisms in order to elucidate how the cytotoxic process occurs. The presence of the following volatile compounds was detected by GC-MS: bicyclogermacrene (12.16%), germacrene D (11.18%), (E)-caryophyllene (9.28%), and α-humulene (8.05%). In general, IC₅₀ values lower than 50μg/mL were obtained for all the tumor cells at 24, 48 and 72h by MTT assay. The decrease in cell DNA content was demonstrated due to the inhibition of the proliferation of Jurkat, Raji and HL-60 cells by B. milleflora essential oil. In particular, Raji cells presented the greatest inhibition of cell proliferation and they were subsequently used to investigate cell death mechanisms. B. milleflora essential oil promoted G0/G1 arrest and also induced cell fragmentation, which was represented by an increase in the sub-G0 population, indicating cell death induced by apoptosis. The selectivity index was 3.97. Necrotic cell death, coupled with low levels of apoptotic cell death, was observed by conventional EB/AO and Hoechst 33342 staining assays, demonstrating that this essential oil acts via both necrotic and apoptotic mechanisms.