According to findings published in the peer-reviewed journal Nutrition, the antioxidant potential of onion extracts was associated with higher activity of antioxidant enzymes and lower levels of in malondialdehyde (MDA - a reactive carbonyl compound and a well-established marker of oxidative stress) in brain tissue.
“The present study may provide extra motivation for the consumption of onions,” wrote researchers from Ajou University School of Medicine in South Korea.
“The results from this study suggest that onion extract may be a beneficial nutrient for the prevention of ischemic [blood-brain barrier] damage, and that the underlying mechanisms may include, at least in part, its antioxidant effects.”
The Korean researchers reduced blood flow in the brain of lab mice and then compared the effects of an onion extract with control animals. Specifically, the researchers looked at dysfunction of the blood-brain barrier, and changes in the activities of antioxidant enzymes catalase and glutathione peroxidase, and on levels of MDA.
Results showed that the content of water in the brain increased following the induced stroke, but this was reduced in onion-treated animals.
In addition, activity of catalase and glutathione peroxidase were maintained in the onion group, compared to the control animals, while increases in MDA levels in brain tissue were reduced.
“During ischemia/reperfusion, [reactive oxygen species] ROS generation is increased and, at the same time, a antioxidant defense system such as catalase and glutathione peroxidase that removes excessive ROS is impaired,” explained the researchers. “ROS are significant contributors to blood-brain barrier (BBB) damage and vasogenic edema, particularly during reperfusion
“Taken together, we suggest that the protective effects of onion extract on brain edema, BBB permeability, and TJs integrity may be, at least partially, associated with its antioxidant effect under ischemia.”
Published online ahead of print, doi: 10.1016/j.nut.2012.02.017
“Onion (Allium cepa) extract attenuates brain edema”
Authors: Soo-Wang Hyun, Mi Jang, Se Won Park, Eun Joo Kim, Yi-Sook Jung