A unique property of the photodynamic signal transduction inhibitor hypericin is functionality in the dark. We show in tumor cells that hypericin targets the heat shock protein (Hsp) 90 chaperone but not Hsp70 (Hsc70) to enhanced ubiquitinylation. As a consequence Hsp90 chaperone functionality is abrogated and the client proteins, mutant p53, Cdk4, Raf-1, and Plk, are displaced from complexes w...

Hypericin is a naturally occurring substance found in the common St. John's Wort (Hypericum species) and can also be synthesized from the anthraquinone derivative emodin. As the main component of Hypericum perforatum, it has traditionally been used throughout the history of folk medicine. In the last three decades, hypericin has also become the subject of intensive biochemical research and is p...

Hypericum perforatum, commonly known as St. John’s Wort, has been found to exhibit many medicinal, especially anti-depressant, properties. Hypericin is thought to be the main chemical constituent responsible for H. perforatum’s medicinal properties. We report here the ability of H. perforatum and hypericin to inhibit the growth of mouse mammary cancer CRL2539 cells. H. perforatum, at concentrat...