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15.01.2011

Piceatannol in rhubarb is NO booster

Rhubarb contains a compound akin to resveratrol that boosts the concentration in the body of the 'good radical' nitrogen monoxide [NO]. Researchers at the Korean Kangwon National University think that analogues of the naturally occurring compound could be developed and used for medicinal purposes. But piceatannol-3'-O-beta-D-glucopyranoside itself is an interesting compound for sports and sex supplements.

Piceatannol occurs in the body when the enzyme CYP1B1 converts resveratrol [see scheme below]. Piceatannol also occurs naturally in berries [J Agric Food Chem. 2004 Jul 28; 52(15): 4713-9.] and red wine. Animal and cell studies suggest that piceatannol inhibits cancer, and a berry-rich diet prevents cardiovascular disease.

The Koreans were curious about the mechanism involved and came up with the theory that piceatannol inhibits the enzyme arginase. Arginase breaks down arginine, forming urea. When arginase works less hard, the body retains more arginine, from which it can make NO. This is actually because of yet another enzyme, nitric oxide synthase. NO in turn relaxes the blood vessels, thus lowering blood pressure and with it the risk of a heart attack or stroke. The immune system uses NO to deactivate cancer cells, and muscle tissue uses NO as a growth stimulus.

An attractive sounding theory. To find out whether it holds water, the Koreans extracted piceatannol-3'-O-beta-D-glucopyranoside [structural formula shown above] from the roots of rhubarb [Rheum undulatum]. Traditional healers in Asia use extracts of rhubarb roots against cardiovascular disease, and recent studies also point to a link with the high concentration of piceatannol in these extracts.

When the researchers added piceatannol to human blood vessel cells, the activity of the arginase enzyme decreased and the emission of NO increased.

The researchers did similar tests with kidney and liver cells and pieces from the aorta. They all had the same results: piceatannol inhibits arginase and boosts NO synthesis. Interesting stuff for stacking with arginine, this rhubarb.

Source:
Exp Mol Med. 2010 Jul 31;42(7):524-32.