Semi-purified extracts of Commelina benghalensis (Commelinaceae) induce apoptosis and cell cycle arrest in Jurkat-T cells

BACKGROUND Commelina benghalensis (CB) is a small plant whose fleshy stems are used in South Africa to treat skin conditions (e.g., cancerous skin outgrowths). This study was aimed at evaluating the effect of sub-fractions of acetone extracts of CB stems on growth-associated molecular events of apoptosis and cell division cycle of Jurkat-T (JT) cells. METHODS Acetone extract of CB stems were subfractioned into n-hexane (F1) and dichloromethane (F2) fractions. After treatment of JT cells with these subfractions, cell proliferation, viability and apoptosis were determined using a haemocytometer, the trypan blue dye exclusion assay, and Hoechst 33258 staining, respectively. Cell division cycle distribution profiles were analysed using an Epics Alba Flow Cytometer and the expression of cell division cycle regulatory genes was analysed using RT-PCR, while immunoreactive proteins were detected on western blots. RESULTS The F1 and F2 fractions inhibited the proliferation and viability of JT cells in a concentration- and time-dependent manner, with IC50 values of 32.5 μg/mℓ and 56 μg/mℓ, respectively. The observed cytotoxicity was established to be a consequence of apoptosis. as verified using Hoechst staining method. Both fractions induced a G1/S interphase arrest of the cell division cycle of JT cells.RT-PCR analyses showed an up-regulatory effect by the F1 fraction in the expression of cyclin B1, cdc2 and bax, with a down-regulatory effect in the expression levels of bcl-2. Fraction F1 also increased the protein expression levels of p53 and its downstream regulators, p21 and Cdc2. However, protein Bax and p21 and p53 transcripts were undetectable under the same experimental conditions. On the other hand, fraction F2 increased the mRNA expression levels of bax, bcl-2, cyclin B1 and cdc2. Concomitantly, fraction F2 showed an up-regulation in the protein expression levels of Cdc2, Bcl-2, Cyclin B1 and p21. Despite the up-regulation in protein expression levels by fraction F2, there was no observable expression levels of the p53 protein and p21 and p53 mRNAs under similar experimental conditions. CONCLUSION These findings suggest that the F1 and F2 fractions of CB may provide a valuable lead for the development of novel and effective anti-neoplastic drug(s).