A terpenoid lactone derived from Azadirachta indica (Neem tree) that displays a variety of biological activities including anti-malarial and anticancer activity. Recently it has also been shown that nimbolide sensitizes colon cancer cells to TRAIL-induced apoptosis through three distinct mechanisms: reactive oxygen species and ERK-mediated up-regulation of DR5 and DR4, downregulation of cell survival proteins, and up-regulation of pro-apoptotic proteins p53 and Bax.