Isolation and inhibitory activity against ERK phosphorylation of hydroxyanthraquinones from rhubarb.

Five hydroxyanthraquinone compounds were purified from Chinese medicinal herb rhubarb by microwave-assisted extraction and silica gel column isolation. Their structures were identified by spectroscopic analysis. One of them, emodin, was found to block the ERK phosphorylation of PC3 cells at 20 microM. And two other compounds had potent proliferation inhibitory activity on A431 and PC3 cells at 20 microM. Furthermore, crude extracts revealed an antifungal activity stronger than that of purified compounds against several plant pathogens tested. Together, our study suggests that these compounds are biologically active and may lead to development of anticancer medicine.