Andrographolide is a labdane diterpenoid that is the main bioactive component of the medicinal plant Andrographis paniculata. Andrographolide is an extremely bitter substance extracted from the stem and leaves of A. paniculata. Andrographolide is used experimentally in different areas of research including cell signaling, immunomodulation, and stroke. Andrographolide inhibits IL-6 expression at both mRNA and protein levels in a dose-dependent manner. Andrographolide suppresses both IL-6 autocrine loop– and paracrine loop–induced cell signaling including Stat3 and Erk phosphorylation. Furthermore, andrographolide inhibits cell viability and induces apoptotic cell death in both androgen-stimulated and castration-resistant human prostate cancer cells without causing significant toxicity to normal immortalized prostate epithelial cells.