Opuntia ficus-indica var. Jalpa (Nopal) Induces Different Cell Death Mechanisms in Colorectal Cancer Cells Depending on the Extraction Method Used.

Abstract

Opuntia ficus-indica (OF) is a native plant of America with biological properties attributed to flavonoids. There are different extraction methods for these compounds; however, it is unknown how different extraction methods might impact the phytochemical concentration ratios and their associated biological effects. Previous studies reported that OF extracts are cytotoxic to colorectal cancer (CRC) cells; however, the cell death mechanism and selectivity to cancer cells have been barely investigated. The objective of this study is to elucidate how different extraction methods impact the phytochemical concentration ratios, the selectivity, and cell death mechanism induced by OF extract in human (Caco-2, HT-29) and murine (CT-26) CRC cells. Extracts were prepared with 80% methanol and 4 N sodium hydroxide, quantification was measured by HPLC-DAD, and identification was measured by LC/MS- TOF. Cell death characteristics were measured by flow cytometry, and its inhibitions were measured by trypan-blue exclusion assay and morphological changes by microscopy. Immune system cell viability was evaluated by MTT. Methanolic extract has a higher yield of phenolic compounds, which correlates with an increased reduction in CRC cell viability at lower concentrations than alkaline, while being non-toxic to immune system cells. Both extracts induced morphological changes, ROS production, ΔΨm loss, and DNA degradation in CRC cell lines. Both extracts induce different cell death modalities in CRC cells. These findings highlight the relevance of OF with significant antitumor activity and demonstrate how the extraction method impacts the compound profile and the observed biological activity and thus, the cytotoxic mechanism.