Harmine 1 was extracted from the seeds of Peganum harmala. From this natural molecule, a new series of isoxazole derivatives with complete regiospecificity were prepared using 1,3-dipolar cycloaddition reactions with various arylnitrile oxides. Harmine and its derivatives were characterized by 1H NMR, 13C NMR and HRMS. The evaluation of their anti-acetylcholinesterase (AChE), anti-5-lipoxygenase (5-LOX), anti-xanthine oxidase (XOD) and anticancer activities were studied in vitro against AChE, 5-LOX and XOD enzymes, respectively, and in HTC-116, MCF7 and OVCAR-3 cancer cell lines. The prepared derivatives were shown to be inactive against the XOD enzyme (0-38.3±1.9% at 100 M). Compound 2 exhibited the best anti-AChE activity (IC50=1.9±1.5 µM). Derivatives 3a, 3b and 3d had moderate cytotoxic activities (IC50=5.0±0.3 µM (3a) and IC50=6.3±0.4 µM (3b) against HCT 116 cells, IC50=5.0±1.0 µM (3d) against MCF7 cells).