Investigation of chemopreventive and apoptotic characteristics of turkish medicinal plant rheum ribes

Uyar, Pembegül
Rheum species are medicinally important plants due to the presence of anthracene derivatives and in this study antioxidative, cytotoxic, apoptotic and chemopreventive characteristics of R. ribes extracts were evaluated. R. ribes shoot and root dry powder samples were prepared and extracted with ethyl acetate, ethanol and water. The extracts were revealed to be a potential scavenger of DPPH radicals and the chemical composition of the extracts was quantified by colorimetric determination of total phenol (GAE) and flavonoid (CAE) contents. HL–60 cells were cultured in the presence of various concentrations of extracts up to 72 hr. R. ribes inhibited the surviv al of HL-60 cells in a concentration- and time-dependent manner, shown by trypan blue and XTT. R. ribes caused HL-60 cells apoptosis via formation of phosphatidylserine externalization, as evidenced by flow cytometry. Exposure of HL-60 cells to higher concentrations of extracts for 72 h resulted in a shift of 87% of the cell population from normal to the early/late apoptotic stage. The R. ribes induced apoptosis may be partially attributed to the activation of caspase-3 and up-regulation of caspase-3 expression was detected in western blot. The significant release of cytochrome c from the mitochondria into the cytosol was observed. The mRNA expression ratio of Bax/Bcl-2 was increased. The apoptosis was also demonstrated by DNA ladder and TUNEL. Chemopreventive effects of R.ribes were investigated at the gene level of CYP1B1 and CYP1A1, and GST enzyme activity against cDNB and concluded that R.ribes modulated activities of these enzymes generally at a time dependent level. T h ese findings suggest that Rheum ribes exhibits potential antioxidant and anticancer properties by inducing caspase-dependent cell death in HL-60 cells.