Toxic plant extracts form basis of stroke treatments

By Wai Lang Chu

- Last updated on GMT

A toxic group of plant extracts has been found to protect animal
tissue against the lack of blood that occurs in stroke giving rise
to a new direction in the development of stroke treatment.

The compound was shown to provide neuroprotection from the damaging effects of depriving a brain of oxygen and glucose and could give hope to stroke victims that may otherwise have suffered some residual damage.

At the moment, no treatment can cure a stroke, and most people will have some form of residual damage, which will vary from person to person. Patients who survive can experience brain damage that leads to loss of language and cognitive ability and permanent extremity weakness, among other problems.

The researchers from Duke University Medical Center in North Carolina, detailed a study in which they screened a broad range of drug like compounds in brain slices taken from rats.

Of the thousands of compounds tested, the researchers found that the cardiac glycoside neriifolin had a particularly potent protective effect against ischemic damage - the destruction of areas of the brain caused when blood supply stops

Neriifolin is a cardiac glycoside a drug group that also includes the cardiac drug digoxin.

Donald Lo, director of the Center for Drug Discovery and associate professor of neurobiology at Duke, and primary investigator on the study said that cardiac glycosides may exert their beneficial effect during stroke in an analogous manner, by restoring calcium to healthy levels in brain cells and thereby preventing cell death.

Calcium plays a key role in regulating normal cell function, and any changes in its cellular concentration - such as those caused by stroke - can be toxic.

Further tests revealed that Neriifolin displayed neuroprotective properties even after six hours had passed after the brain tissue was starved of oxygen and glucose.

"This discovery is exciting because it may lead to interventions to prevent or lessen the amount of brain damage suffered after stroke,"​ said Lo.

Stroke is the third leading cause of death in the US, with more than 700,000 new cases diagnosed each year. Strokes occur when the blood supply to the brain is cut off either by a blood clot or the bursting of an artery.

Currently, only one drug has been approved by the FDA to treat stroke. Called recombinant tissue plasminogen activator, the drug must be given within a three-hour window after the onset of stroke.

Also, because the drug is delivered intravenously and acts by breaking blood clots, it is ineffective against "hemorrhagic" strokes that happen when an artery bursts.

"This discovery is very promising,"​ he said. "We are now looking forward to taking this research to the next step and testing neriifolin and other cardiac glycosides further in animal models and hopefully, someday, in humans."

The findings will appear during the week of June 19, 2006, in the early online edition of the >Proceedings of the National Academy of Sciences​ and in the July 5 printed issue of the journal.

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