Alizarin is an anthraquinone dye for detecting the presence of calcium salts [1].

Alizarin belongs to the anthraquinone group. It is a chelator for calcium and is commonly used to stain the calcifying or calcio-receptive zone of the collagenous matrix where calcium salts are being deposited. On the other hand, the Alizarin complexone is used for bone staining in vivo to study bone remodeling [1].

Alizarin is proved to have anti-tumor efficacy. It suppresses the cell growth of the prostate cancer, breast cancer and osteosarcoma cell lines in vitro. Among these, the osteosarcoma cells appear to be most sensitive. The IC50 values of Alizarin against three osteosarcoma cell lines Saos-2, MG-63 and U-2 OS are 27.5, 29 and 69.9μg/ml, respectively. Alizarin inhibits the cell growth through cell proliferation blockade rather than induction of apoptosis. It inhibits the phosphorylation of ERK. In addition, Alizarin is also found to induce S-phase arrest as well as a decrease of the G0/G1 and G2/M phases [1].

References:
[1] Fotia C, Avnet S, Granchi D, Baldini N. The natural compound Alizarin as an osteotropic drug for the treatment of bone tumors. J Orthop Res. 2012 Sep;30(9):1486-92.