Source: Roman Bystrianyk, "Quercetin and Vitamin C May Protect the Brain", Health Sentinel, February 7, 2005
According to the Alzheimer’s Association, an estimated 4.5 million Americans have Alzheimer’s disease, with the number of Americans with Alzheimer’s more than doubling since 1980. Also, according to the National Institutes of Health, Parkinson's disease affects between 1 and 1.5 million individuals in the United States, with some 20,000 new cases diagnosed each year. This means that an estimated 200 people in every 100,000 suffer from Parkinson's disease.
A study published in the December issue of the Journal of Agricultural and Food Chemistry looks at how oxidative stress plays a role in these conditions and the shielding effect of quercetin and vitamin C in protecting the brain from this damage. There is evidence that oxidative stress plays a role in Alzheimer and Parkinson's diseases. It appears that oxidative stress causes cumulative damage and could be responsible for the late life onset and slow progression of these illnesses. Brains cells are rich in polyunsaturated fats and because of lower levels of antioxidant chemicals, such as glutathione, in the brain; these cells are especially vulnerable to free radical attack. Vitamin C is a water-soluble antioxidant that has been shown to help decrease the risk of Alzheimer’s. Quercetin is a flavonoid that has antioxidant and free radical scavenging properties.
The authors of the study exposed cell cultures to oxidative stress in the form of hydrogen peroxide (H202), with some cells pretreated with different amounts of quercetin or vitamin C. Those cells that were pretreated with quercetin or vitamin C were significantly more protected than those that were not pretreated. The protection was dose dependent with quercetin having a higher protective effect than vitamin C. There was a 4-fold increase in cell viability with those neuronal cells treated with quercetin or vitamin C at the highest dose. The authors state that, “our data also showed that quercetin has more cell protective effect than vitamin C. These results suggest that quercetin and vitamin C with excellent antioxidant activities could protect the neuronal cell membrane against H202-induced neurotoxicity, although the protective effect of vitamin C was not strong compared to that of quercetin.”
Because of the blood-brain barrier (BBB), many chemicals cannot pass into the brain, thus limiting drug delivery to the brain. It has been shown that quercetin can flux into the brain. The authors conclude that, “it is possible that quercetin with beneficial antioxidant and biological functions is able to penetrate the BBB and can protect the H202-induced cytotoxicity.”
Study reference: Journal of Agricultural and Food Chemistry, December 15, 2004