Comparative Assessment of the Antioxidant and Anticancer Activities of Plicosepalus acacia and Plicosepalus curviflorus: Metabolomic Profiling and In Silico Studies

This study presents a comparison between two mistletoe plants—P. acacia and P. curviflorus—regarding their total phenolic contents and antioxidant and anticancer activities. P. curviflorus exhibited a higher total phenolics content (340.62 ± 19.46 mg GAE/g extract), and demonstrated higher DPPH free radical scavenging activity (IC(50) = 48.28 ± 3.41µg/mL), stronger reducing power (1.43 ± 0.54 mMol Fe(+2)/g) for ferric ions, and a greater total antioxidant capacity (41.89 ± 3.15 mg GAE/g) compared to P. acacia. The cytotoxic effects of P. acacia and P. curviflorus methanol extracts were examined on lung (A549), prostate (PC-3), ovarian (A2780) and breast (MDA-MB-231) cancer cells. The highest anticancer potential for the two extracts was observed on PC-3 prostate cancer cells, where P. curviflorus exhibited more pronounced antiproliferative activity (IC(50) = 25.83 μg/mL) than P. acacia (IC(50) = 34.12 μg/mL). In addition, both of the tested extracts arrested the cell cycle at the Pre-G1 and G1 phases, and induced apoptosis. However, P. curviflorus extract possessed the highest apoptotic effect, mediated by the upregulation of p53, Bax, and caspase-3, 8 and 9, and the downregulation of Bcl-2 expression. In the pursuit to link the chemical diversity of P. curviflorus with the exhibited bioactivities, its metabolomic profiling was achieved by the LC-ESI-TOF-MS/MS technique. This permitted the tentative identification of several phenolics—chiefly flavonoid derivatives, beside some triterpenes and sterols—in the P. curviflorus extract. Furthermore, all of the metabolites in P. curviflorus and P. acacia were inspected for their binding modes towards both CDK-2 and EGFR proteins using molecular docking studies in an attempt to understand the superiority of P. curviflorus over P. acacia regarding their antiproliferative effect on PC-3 cancer cells. Docking studies supported our experimental results; with all of this taken together, P. curviflorus could be regarded as a potential prospect for the development of chemotherapeutics for prostate cancer.