Anti-Proliferative, Cytotoxic and Antioxidant Properties of the Methanolic Extracts of Five Saudi Arabian Flora with Folkloric Medicinal Use: Aizoon canariense, Citrullus colocynthis, Maerua crassifolia, Rhazya stricta and Tribulus macropterus

Saudi Arabian flora have a history of use as folklore remedies, although such properties have yet to be explored rigorously, and the safety of such remedies should be assessed. This study determined the anti-proliferative, cytotoxic, and antioxidant properties of extracts of the following five plants indigenous to Saudi Arabia: Aizoon canariense, Citrullus colocynthis, Maerua crassifolia, Rhazya stricta, and Tribulus macropterus. The aerial parts of the five plants were collected from various locations of the western and northern regions of Saudi Arabia and used to prepare methanolic extracts. Three approaches were used to determine the proliferation and cytotoxicity effects using HaCaT cells: MTT, FACS, and confocal microscopy. Meanwhile, two approaches were used to study the antioxidant potential: DPPH (acellular) and RosGlo (cellular, using HaCaT cells). C. colocynthis possessed anti-proliferative activity against HaCaT cells, showing a significant decrease in cell proliferation from 24 h onwards, while R. stricta showed significant inhibition of cell growth at 120 and 168 h. The IC(50) values were determined for both plant extracts for C. colocynthis, with 17.32 and 16.91 µg/mL after five and seven days of treatment, respectively, and for R. stricta, with 175 and 105.3 µg/mL after five and seven days of treatment. R. stricta and M. crassifolia exhibited the highest capacities for scavenging the DPPH radical with IC(50) values of 335 and 448 µg/mL, respectively. The subsequent ROS-Glo H(2)O(2) assay confirmed these findings. The R. stricta and M. crassifolia extracts showed potent antioxidant activity in both acellular and cellular models. The C. colocynthis extract also demonstrated significant anti-proliferation and cytotoxic activity, as did the R. stricta extract. These properties support their usage in folk medicine and also indicate a further potential for development for holistic medicinal use or as sources of new active compounds.