Antibacterial, Antitumor (Lung Cancer Cell H292) and Antioxidant Properties of Sicilian Prickly Pear Cactus (Opuntia Ficus-Indica) Cladode Extracts

Background: Methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) strains can colonize the lower respiratory tract, causing severe bacterial pneumonia. Such infections frequently occur in oncologic patients affected by lung cancer. Therefore, the present study aimed to explore the potential antibacterial and cytotoxic properties of Opuntia ficus-indica acetone and Opuntia ficus-indica diethyl ether extracts (OFI AE and OFI DEE) against Staphylococcus aureus strains and human mucoepidermoid pulmonary carcinoma cell line H292, respectively. In addition, the antioxidant activity of the two extracts was evaluated. Methods: The antimicrobial activity of OFI AE and OFI DEE against MSSA and MRSA strains was evaluated through the microdilution method. The antibiofilm effect of OFI extracts was determined by the crystal violet assay. Moreover, the potential synergistic activity between OFI extracts and the antibiotic Gentamycin (GEN) was tested using the checkerboard assay. The cytotoxic activity against H292 cells was investigated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrasodium bromide (MTT) and flow cytometry assays. Furthermore, oxidative stress and antioxidant capacity of the extract were measured by extracellular reactive oxygen species (ROS) formation and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. Finally, the chemical composition of the two phytoextracts was analyzed by Ultra High-Performance Liquid Chromatography-Mass Spectrometry. Results: Our results show that both extracts inhibited the growth of MSSA and MRSA strains, although they were not able to counteract biofilm formation. However, the combination of the extracts with GEN potentiated the activity of the antibiotic treatment. Furthermore, OFI AE treatment showed a potent cytotoxic effect on H292 cells following ROS formation. Finally, both extracts showed no significant antioxidant activity and the chemical analysis revealed a high content of polyphenols and flavonoids, which could be responsible for the observed biological effects of the OFI extracts. Conclusions: OFI extracts are a promising natural source of antibacterial and anticancer agents endowed with beneficial effects on human health.