Natural compounds have proven to be a treasure trove of medicinal properties. For example, the bark of the Pacific yew tree yielded a compound that has helped battle some forms of cancer. Such finds have led to a new industry--bioprospecting--and such prospectors have fanned out across the globe in search of nature's remedies. Now a compound isolated from coral collected off the coast of Okinawa has shown the ability to slow down and possibly prevent virus replication and it may hold promise as a cancer treatment.
Isis hippuris is a yellow, branching coral found in the tropical waters of the western Pacific. By grinding it up and treating it with methanol, researchers isolated a natural steroid, dubbed hippuristanol. Biochemist Jerry Pelletier of McGill University and his colleagues tested this steroid's therapeutic abilities. In vitro and in vivo, the steroid blocked a critical step in the process that allows a virus to thrive.
Antibiotics and other modern medicines do not work on viruses because these radically simple organisms infiltrate cells and hijack their processes to serve their own purposes. Such a hijacker virus uses cellular machinery to control the process of building proteins and thereby replicates itself. Based on the team's research, published online yesterday in Nature Chemical Biology, hippuristanol stops this process by inhibiting the function of a protein--eIF4A--that acts as a molecular motor, which the virus relies on to make proteins. "You can selectively block production of proteins from viral mRNAs that rely more heavily on this factor," Pelletier says. "It's very clean in the way it acts on this protein. It's very selective in its mechanism and it doesn't appear to have off-target effects."
These experiments showed that hippuristanol slowed the replication of poliovirus without stopping protein creation in uninfected cells. And because this process appears to spiral out of control in some cancers, hippuristanol might also prove to be a potent chemotherapy. "Any compound that targets these factors opens up a new therapeutic avenue for cancer," Pelletier notes. The only problem will be ensuring a steady supply of the promising compound without denuding the western Pacific's reefs.