By Stephen Daniells
21/01/2008 - Antioxidant compounds in citrus fruit may have a role to play in protection against neurodegenerative diseases, suggests a new lab study from Taiwan.
The flavanones hesperidin, hesperetin, and neohesperidin were shown to protect against the toxicity of hydrogen peroxide (H2O2), as well as protecting against DNA damage, states the study published in the Journal of Agricultural and Food Chemistry.
"These results first demonstrate that the citrus flavanones hesperidin, hesperetin, and neohesperidin, even at physiological concentrations, have neuroprotective effects against H2O2-induced cytotoxicity in PC12 cells," wrote the authors from National Chung Hsing University and Food Industry Research and Development Institute.
"These dietary antioxidants are potential candidates for use in the intervention for neurodegenerative diseases."
One such disease that is mentioned Alzheimer's disease - the most common form of dementia and currently affects over 13 million people worldwide. The direct and indirect cost of Alzheimer care is over $100bn ( 81bn) in the US alone. The direct cost of Alzheimer care in the UK was estimated at £15bn ( 22bn).
Although the mechanism of Alzheimers is not clear, more support is gathering for the build-up of plaque from beta-amyloid deposits. The deposits are associated with an increase in brain cell damage and death from oxidative stress.
It is against the oxidative stress that the flavanones appear to offer protection.
Sam-Long Hwang and Gow-Chin Yen incubated PC12 cells with different concentrations of hesperidin, hesperetin, and neohesperidin (0.8, 4, 20, and 50 micromoles) and then exposed the cells to H2O2 (400 micromoles).
The researchers report that all three flavanones inhibited the decrease in cell loss at all test concentrations, as well as preventing membrane damage, scavenging reactive oxygen species, and increasing the activity of the antioxidant enzyme catalase.
Furthermore, incubation with hesperidin and hesperetin decreased DNA damage in the cells, while also inhibiting the decrease of glutathione peroxidase and glutathione reductase activities.
"In summary, hesperidin, hesperetin, and neohesperidin have neuroprotective effects against H2O2-induced cytotoxicity in PC12 by diverse mechanisms, suggesting that these flavanones may be useful in more complete intervention for neural disorder," wrote the authors.
"However, mechanisms underlying the neuroprotective activity of these
flavanones against oxidative stress at physiological concentrations other than those mentioned in the present study need further investigation.
"Moreover, the present data suggest that citrus fruits have potential as functional foods for neuroprotection," they concluded.
Previously, research into citrus flavanones has reported that hesperidin and naringin possess potential heart healthy benefits, and can lead to reductions in cholesterol levels by about 25 per cent in lab animals (Journal of the Science of Food and Agriculture, doi: 10.1002/jsfa.2834). There have also been reports of the compounds possessing anti-inflammatory activity, anticarcinogenic effects and boosting bone health.
Moreover, hesperidin has received attention from scientists at the Nestlé Research Center, who reported that enzymatic modification can increase the bioavailability of the compound by changing the absorption site in the intestine (Journal of Nutrition, Vol. 136, pp. 404-408).
The result may eventually lead to a range of functional ingredients with improved bioavailability that "in principle, should work in any food matrix," lead researcher, Dr. Gary Williamson from Nestlé Research Center, told NutraIngredients.com in 2006.
Source: Journal of Agricultural and Food Chemistry
Published on-line ahead of print, doi: 10.1021/jf072826r
"Neuroprotective Effects of the Citrus Flavanones against H2O2-Induced Cytotoxicity in PC12 Cells"
Authors: S.-L. Hwang, G.-C. Yen
http://www.nutraingredients.com/news/ng.asp?n=82662-citrus-flavanones-hesperidin-alzheimer-s 
