Rhein Methylate is an intermediate in synthesizing Rhein 8-Glucoside (R318520), which has been seen to exhibit cytotoxic and DNA-damaging properties towards tumor and normal human cells. In addition it has been shown to be an inhibitor of PTP1B (Human Protein Tyrosine Kinase 1B) in vitro. It is an analog of Rhein (318500) which is found in the free state and as glucoside in Rheum spp, Polygonaceae (rhubarb) and in Senna leaves. It is a potential antioxidant resource: endophytic fungi from medicinal plants.