The O. natrix belongs to the family Fabaceae and is distributed in Jordan. Different species of the family Fabaceae contain chemical compounds that may have potential antiproliferative, antidiabetic, and anti-Alzheimer’s disease. High-performance liquid chromatography (HPLC) was applied to analyse the phenolic compounds found in O. natrix methanolic extract. Using the MTT assay, the antiproliferative action was studied. The enzymes α-glucosidase and butyrylcholinesterase inhibition assays were used to study the antidiabetic and anti-Alzheimer’s disease actions, respectively, of methanolic extract of O. natrix. Eleven phenolics and seven flavonoids were identified in the methanolic extract of O. natrix by HPLC. The highest phenolics and flavonoids were gallic acid (1.25 mg/100 g dry weight) and rutin (1.44 mg/100 g dry weight), respectively. The most cancer cell lines influenced by the extract of O. natrix were PC-3 (IC50 = 55 ± 2 µg/mL) and HepG-2 (IC50 = 68 ± 2 µg/mL) compared to positive control cisplatin. However, the cancer cell lines CaCo-2, MCF-7, and HeLa showed IC50 values of 109 ± 2 µg/mL, 123 ± 2 µg/mL, and 79 ± 1 µg/mL, respectively, related to cisplatin. The O. natrix extract inhibited the α-glucosidase enzyme and butyrylcholinesterase enzyme by 84% and 86%, respectively compared to positive controls acarbose and rivastigmine. The O. natrix may possess antiproliferative effects against prostate cancer and hepatocellular carcinoma. It also may have antidiabetic and anti-Alzheimer’s disease effects.