OTC Herbal Supplement Rutin Blocks Blood Clot Formation: Study

A new study has shown that the over-the-counter dietary supplement can inhibit blood clot formation in the blood vessels of mice, suggesting that it could be used to treat and prevent stroke, pulmonary embolism and other conditions in humans.

Clot formation in arteries causes heart attacks and strokes, which are the number one killer of people in western civilization, says Robert Flaumenhaft, a researcher at Harvard Medical School's Beth Israel Deaconess Medical Center.

Flaumenhaft is the senior author of a paper that appeared Tuesday in the Journal of Clinical Investigation detailing rutin's anti-clotting capabilities in mice.

Other investigators have recently discovered that an enzyme called protein disulfide isomerase, or PDI, is involved in blood clot formation. So Flaumenhaft and his lab began looking for a compound that would inhibit PDI.

After screening around 5,000 compounds, Flaumenhaft found that rutin seemed like the best candidate. It's a type of compound called a flavonoid, and occurs naturally in a number of fruits and vegetables, including asparagus, buckwheat, cranberries, and citrus fruits like oranges and lemons.

Rutin is of great interest to us because it's plentiful in many types of foodstuffs and because you can buy 500mg tablets of it at the corner drug store, Flaumenhaft said in a telephone interview.

To see how rutin performs at blocking PDI inside a living body, Flaumenhaft and his team injured blood vessels in mice by zapping them with a laser or using a chemical called ferric chloride. They then found that blood clot formation was inhibited in the vessels of mice that had been given rutin by mouth.

Not all clots are alike - blood clots in veins tend to be richer in a protein called fibrin, while blood clots in arteries are more comprised of aggregates of platelets - fragments of cells. Rutin seems to stop both kinds of clots from forming, according to the paper.

It's still unclear exactly how rutin's target, PDI, promotes blood clot formation, but scientists know that it's involved in getting proteins to fold into certain conformations.

There's some sense that PDI gets the proteins into proper form for clotting to proceed, Flaumenhaft says.

Rutin's ability to inhibit PDI would stop the formation of clots just as tackling a conductor at the symphony would disrupt the orchestra's performance.

Flaumenhaft says his team found they needed higher doses of rutin to inhibit clot formation when they gave the compound to the mice orally instead of by injection. But the amount of rutin they used by body weight of the mice is comparable to the dosage found in human supplements, he says.

What's needed now, Flaumenhaft says, are clinical studies to examines how rutin performs at stopping blood clot formation in human blood vessels.

The fact that rutin is already sold over the counter means it would have a much quicker path through the drug pipeline than newer compounds, which have to go through preclinical testing to show they won't endanger trial patients.

Because this is already a compound that is generally recognized as safe, it can go right to clinical trials, he says.