Evaluation of Opuntia spp. bioactive products as promising natural chemotherapeutical agents- an in vitro approach

Dissertation to obtain a Master Degree in Biotechnology

Recently, prevention of cancer through dietary intervention has received an increasing interest. In particular, dietary polyphenols mainly found in fruits and vegetables have become very attractive as chemopreventive and therapeutic agents. The main aim of this work was to investigate the potential activity of Portuguese Opuntia spp. on colon cancer therapy, as this fruits have been reported to be rich sources of bioactive compounds. Opuntia spp. fruits were collected in different sites of Portugal, namely Tramagal, Beja, Marvão Sines and Quarteira and processed in order to obtain fruit juices, polyphenol-rich concentrates and residues extracts from fruit juices production. All Opuntia products were investigated for antiproliferative activity of human colon cancer cells (HT29). Opuntia juices from Tramagal, Sines and Quarteira were the most effective on cancer cell growth inhibition due to the highest content in total polyphenol content and betalains. The most promising extracts were derived from Quarteira, Sines and Beja fruit juices residues using conventional solvent extraction, adsorption technology and pressurized liquid extraction, respectively. These extracts showed high antiproliferative effect inducing cell cycle arrest in different checkpoints. Additionally, the same extracts showed to induce ROS production in cancer cells, playing an important role in activation of pro-apoptic cell death mechanisms. The capacity of natural extracts in reverting chemoresistance of tumor cells was evaluated on a drug-resistant HT29 cell culture. The product derived from Beja residue using pressurized liquid extraction with 60%CO2 and 40%EtOH showed to increase cells sensitivity to the drug. Opuntia spp. fruits reveled to be promising natural sources for the production of functional products as well as for the development of novel chemotherapeutic agents.