Induction of Apoptosis and Cell Cycle Arrest in two Human Cancer A549 and HT29 Cells Lines by Barhi Date Palm Kernels Extracts and Three Isolated Cytotoxic Compounds

Abstract

Background and objectives: The initiation of apoptotic death in cancer cells is the aim of many chemotherapeutic strategies. As many anticancer agents have been discovered in natural plant sources, the search for novel phytochemicals displaying anticancer activities continues at a tremendous rate. This study was conducted to evaluate the effect of extractable polyphenols (EPP); non-extractable polyphenols (NEPP); nobiletin (NOB); tectorigenin (TEC) and persicogenin (PERS) from Barhi date palm kernels (BDPK) extracts on the induction of apoptosis in human lung cancer A549 and colon cancer HT29 cell lines. Materials and Methods: The anticancer activities were determined using MTT and trypan blue exclusion assays. Flow cytometry analysis was performed to study the cell viability, cell cycle arrest and apoptosis. The underlying mechanism of apoptosis induced by crude extracts and the purified compounds was investigated using caspase-3, -8 and -9 assays and the mitochondrial membrane potential assay. Results: The findings indicate that both BDPK extracts and the purified compounds do exert induced cell death on A549 and HT29 cells. The results observed from MTT- assay and trypan blue exclusion indicate that the cytotoxic effects of both plant extracts and the three isolated flavonoids are dose-dependent with higher cell death after 72 hours treatment. Treatment of human lung and colon cancer cells with EPP, NEPP, NOB, TEC and PERSI induced late stages of apoptosis as there was evidence of the DNA degradation and high percentage of the cells population was situated at sub-G1 phase, indicating a high population of apoptotic cells. Conclusions: Study of the apoptotic mechanism demonstrated that EPP and NEPP exhibited dependent mitochondrial signalling pathway as seen with caspase-9 and induced receptor-mediated (extrinsic) apoptotic pathway as seen with caspase-8. Therefore, our results suggest that BDPK extracts and the three isolated flavonoids could be a good candidate for developing anticancer agents.

Effects of Time, Temperature, and Solvent Ratio on the Extraction of Non-Extractable Polyphenols with Anticancer Activity of Barhi Date Palm Kernels Extracts Using Response Surface Methodology

“…Our previous work [13] confirmed that the NEPP extracts of BDPK demonstrated selective cytotoxicity towards human lung (A549) and colon cancer (HT29) cell lines while being less cytotoxic against the normal cells. Such selective cytotoxic activity suggested that the "active substances interacted with special cancer-associated receptors or cancer cell special molecule, thus triggering some mechanisms that cause cancer cell death" [41].…”

“…The extraction of polyphenols from plant materials is strongly influenced by many factors; extraction time, temperature and solvent-to-sample ratio among other factors [31,32]. Since the previous results [13] indicated that the EPP from BDPK were strong antioxidants and showed cytotoxic effects in selected human cancer cells, this research was carried out with the aim of optimising critical process parameters (extraction temperature, time and solvent/sample ratio) affecting the extraction of NEPP from BDPK using RSM in order to simultaneously maximise possible extraction of the TPC, TFC, TPAC with high DPPH• scavenging capacity and anticancer effects of NEPP extracts on A549 and HT29 human cancer cells.…”

“…The potential antiproliferative/cytotoxic effect of non-extractable (NEPP) extracts against two human cancer cells lines (A549 and HT29) was tested using MTT assay. For screening, the cells were treated with the NEPP extracts at 0-1000 μg/ml concentration [13]. The IC50 (inhibiting 50 % of cell growth) values of NEPP extracts were measured, and their direct antiproliferative/cytotoxic effects were determined.…”

“…The NEPP extracts showed a selective antiproliferative effect against the two human cancer cell lines, A549 and HT29. Interestingly, the normal cell lines, 3T3 showed good resistance with median inhibitory concentration (IC50) values of higher than 100 µg/mL of NEPP extracts of BDPK [13]. The IC50 values for the active extracts and the respective standard reference drug (paclitaxel) were calculated for the two tested cell lines after 24 and 72 h of incubations [13].…”

“…Additionally, DPK extracts have shown some positive molecular activities, including prevention or management of neurodegenerative diseases [6], inflammation [8] and cancer [9,10]. Previous studies suggested that the polyphenolic compounds are primarily responsible for the antioxidant and biological activities of DPK [3,7,11], and this was experimentally confirmed in the lab [12,13].…”