A further compound identified in grapes may fight cancer and diabetes
according to researchers with the U.S. Department of Agriculture.The
compound, pterostilbene, is similar to resveratrol.
Previous studies by others have demonstrated that pterostilbene
also has anti-diabetic properties. The current study is the first
to identify it as a cancer-preventive agent, however.
The study adds to the growing health benefits of grapes said
Agnes M. Rimando, Ph.D., lead investigator for the study and a
research chemist with the USDAs Natural Products Utilization
Research Unit in Oxford, Miss.The research, limited to laboratory
studies of cells, could lead to more healthful varieties of grapes
and the design of better drugs to fight cancer and diabetes. Prompted
by the structural similarity of pterostilbene to resveratrol,
Rimando decided to test the compound to determine if it had similar
anticancer and antioxidant activities. In lab tests using mouse
mammary cells, pterostilbene prevented a type of cell damage that
is normally induced by cancer-causing agents. . Earlier studies
by the researcher showed that the compound is toxic to a human
breast cancer cell line. It appears that pterostilbene is equal
in potency to resveratrol as a cancer-preventive agent.The similar
effect is likely due to their high antioxidant activity. Antioxidants
destroy free-radicals, highly reactive molecules whose excess
has been linked to cancer.Pterostilbene has another benefit not
found in resveratrol. Animal studies by others have shown that
the compound can lower blood glucose and may be a potent antidiabetic
agent. At least one study showed that it could lower plasma glucose
levels in rats with high blood sugar by 42 percent, comparable
to at least one known antidiabetic agent (metformin), according
to the researcher.
Both pterostilbene and resveratrol belong to a group of chemicals
called phytoalexins, which are produced by plants in response
to fungal infection, ultraviolet light, and various chemical and
physical stressors. While both exhibit strong antifungal activity,
pterostilbene appears to be 60 to 100 times more potent as a fungicide,
a property that may one day be exploited by farmers in search
of a more disease-resistant grape, says Rimando.
In plants that contain these chemicals, their content usually
differs dramatically. Quantitative studies have shown that for
every 10 parts resveratrol, theres only 1-2 parts pterostilbene.
The relationship between the two similar compounds and their unequal
content in plants is unclear, but remains the subject of ongoing
studies. Dark-skinned grapes are likely to contain the most pterostilbene.
For reasons that are unclear, pterostilbene is not normally found
in wine,Rimando says. This may be because it is unstable in light
and air, which makes it less likely to survive the wine-making
Source: Rimando AM et al. Cancer Chemopreventive and Antioxidant
Activitiesof Pterostilbene, a Naturally Occurring Analogue of