Anticancer Potential and Phytochemical Constituents of Ononis natrix Grown in Lebanon

Chemotherapy faces numerous challenges, like drug resistance, severe side effects, and high costs, highlighting the need for effective and affordable alternative treatments. Natural products offer promising candidates, with Ononis species known for diverse biological activities owing to phenolic compounds. This study represents the first phytochemical and pharmacological investigation of Lebanese Ononis natrix . Using chromatographic techniques and spectroscopic analysis, five compounds were isolated and identified as follows: 8-hydroxy-6-methoxy-3-undecyl-3,4-dihydroisocoumarin (O1), gardenin B (O2), 5-demethylnobiletin (O3), 5-(2-hydroxytridecyl)benzene-1,3-diol (O4), and pectolinarigenin (O5). Compounds O3 and O4 are reported for the first time in Ononis species, with O4 being rare. The crude extract’s (CE) and isolated compounds’ anticancer activities were assessed against the human colon adenocarcinoma cell line (HT-29) and the human non-small cell lung cancer cell line (H460) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results revealed significant inhibitory activities of compounds O4 and O5 against both cell lines, with IC 50 values between 21–23 µM and 32–34 µM, respectively. Interestingly, all the tested compounds and the CE showed either synergistic or additive effects when used in combination with a chemotherapeutic agent (sorafenib), achieving the same efficacy at reduced sorafenib doses (2.5 and 5 µM) and an enhanced inhibitory effect at the standard dose (10 µM). Structure-activity relationship analysis correlated O4’s activity to the long side chain at C-5 and O5’s to the hydroxyl and methoxy groups. These preliminary findings highlight the medicinal importance of Lebanese O. natrix in vitro, but no conclusion can be drawn regarding its therapeutic benefit. Further investigations are recommended to explore the remaining components and determine their biological activities and mechanisms of action.