– (E)-2-(2-Chlorostyryl)-3,5,6-trimethylpyrazine (CSTMP) is a stilbene derivative with antioxidant and anticancer activities. It stimulates proliferation of hydrogen peroxide-damaged ECV-304 cells (EC50 = 24.9 nM). CSTMP reduces hydrogen peroxide-induced release of lactate dehydrogenase (LDH) in and increases viability of human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner via inhibition of apoptosis. It reverses hydrogen peroxide-induced release of malondialdehyde (MDA) and decreases in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities as well as increases constitutive nitric oxide synthase (cNOS) activity and nitric oxide (NO) production in HUVECs. CSTMP also induces cell death of A549 non-small cell lung cancer (NSCLC) cells in an IRE1α-dependent manner through induction of IRE1α-TRAF2-ASK1 complex-mediated endoplasmic reticulum (ER) stress and mitochondrial apoptosis.