Quercetin could lower Alzheimer’s and other disease risk In an article that will appear in the December 1 2004 issue of the American Chemical Society’s Journal of Agricultural and Food Chemistry, researchers at Cornell University found that quercetin, an antioxidant compound that occurs in apples, onions, berries and other fruit, helps prevent oxidative damage to brain cells that could contribute to Alzheimer’s disease and other disorders.
Alzheimer’s disease is characterized by the overproduction of beta-amyloid protein in the brain, which is believed by some researchers to create free radicals that cause cumulative brain cell damage.
Professor and chairman of the Department of Food Science and Technology at Cornell University, C.Y. Lee, PhD and colleagues exposed rat brain cell cultures to hydrogen peroxide, a compound that causes free radical damage, which is believed to occur in Alzheimer’s disease. The cell cultures were pretreated with quercetin or vitamin C, or received no pretreatment.
Cells that received the quercetin pretreatment experienced significantly less damage to DNA and cellular proteins and had improved viability compared to those exposed to vitamin C or no pretreatment, demonstrating a protective effect for quercetin against neurotoxicity. Vitamin C was also effective, but to a lesser degree than quercetin.
The findings add to those of a growing body of research that Alzheimer’s and other disease risks could be lowered by dietary means, particularly by increasing antioxidant intake. Dr Lee commented, “On the basis of serving size, fresh apples have some of the highest levels of [the antioxidant] quercetin when compared to other fruits and vegetables and may be among the best food choices for fighting Alzheimer’s.”
Alzheimer’s disease Oxidative stress is very important in the development of Alzheimer's disease. Antioxidant supplements help block this process. "Beta-amyloid is aggregated and produces more free radicals in the presence of free radicals; beta-amyloid toxicity is eliminated by free radical scavengers" (Grundman 2000).
Free-radical damage (oxidative stress) is a significant cause of biological aging. It is well-known that neurons are extremely sensitive to attacks by destructive free radicals. The following evidence supports the hypothesis of free-radical damage being a central cause in Alzheimer's disease (Christen 2000):
The brain lesions present in the brains of Alzheimer's disease patients are typically associated with attacks by free radicals (for example, damage to DNA, protein oxidation, lipid peroxidation, and advanced glycosylation end products).
Metals (such as iron, copper, zinc, and aluminum) are often present. These metals have a catalytic activity which produces free radicals.
Beta-amyloid is aggregated and produces more free radicals in the presence of free radicals.
Beta-amyloid toxicity is eliminated by free radical scavengers.
Apolipoprotein E (ApoE) is subject to attacks by free radicals, and apolipoprotein E peroxidation has been correlated with Alzheimer's disease. In contrast, apolipoprotein E can act as a free radical scavenger.
Alzheimer's disease has been linked to mitochondrial anomalies affecting cytochrome c oxidase. These anomalies may contribute to the abnormal production of free radicals.
Free radical scavengers (such as vitamin E, selegeline, and ginkgo biloba extract) have produced promising results in Alzheimer's disease.
Red wine contains resveratrol, but the quantity varies depending on where the grapes are grown, the time of harvest, and other factors. After more than two years of relentless research, a standardized resveratrol extract is now available as a dietary supplement. This whole grape extract contains a spectrum of polyphenols that are naturally contained in red wine such as proanthocyandins, anthocyanins, flavonoids, etc.
The resveratrol used in this product is extracted from organic grapes and is in a natural matrix that includes many other polyphenols. Quercetin is added to enhance the bioavailability of the resveratrol.