A β-carboline alkaloid and an active metabolite of harmaline; an inhibitor of DYRK1A (IC50 = 0.63 µM); an inhibitor of MAO-A (IC50 = 0.66 µM); selective for DYRK1A over Cdk1, Cdk5, CK1α1, Clk4, DYRK2, Pim-1, and GSK3β but also inhibits DYRK1B and Clk1 at 10 µM; inhibits proliferation of H4 human glioblastoma cells (IC50s = 23.7 µM); reduces TCDD-induced increases in CYP1A1 levels in HepG2 cells and prevents TCDD-induced activation of AhR in guinea pig hepatic cytosolic extracts; reduces glutamate-induced cytotoxicity, cytochrome c release, caspase-3 activation, and ROS production in PC12 cells at 25 µM