The doses responsible for the apparent neuroprotective effects are produced at“levels approaching the concentrations found in human plasma”,report the researchers in the European Journal of Nutrition.
The researchers analyzed the potential of metabolites of two wild varieties of blackberry, Rubus brigantinus and Rubus vagabundus, which grow naturally in the north of Spain and Portugal.
“These two species have, until now, not been chemically characterized,” explained the researchers.
“The occurrence of different (quantities of) phenolic compounds could promote different bioactivities, thereby identifying this germplasm as sources of compounds to be further explored and exploited.”
Metabolites of the wild blackberry extracts were found to reduce levels of reactive oxygen species (ROS) in cells, as well as activating enzymes called caspases, which play an important role in cell death (apopotosis).
While caspase activation is usually associated with cell death (and therefore neurodegeneration), for the wild blackberry extracts, the increase in caspase activity was not accompanied by a reduction in cell viability, said the researchers.
“Exposure to components in the digests from wild blackberries could be an initiating event that leads to protection against subsequent, potentially lethal stimuli,” they postulated.
“This mechanism, also known as preconditioning or hormetic effect, has been reported as an effective neuroprotective mechanism, where activation of caspase-3 could be involved.
“This is the first report highlighting a neuroprotective effect by a digested food matrix involving activation of caspases, suggesting a preconditioning effect.”
Led by Claudia Santos from the New University of Lisbon in Portugal, the researchers analyzed differences in the polyphenol content of wild blackberries, R. brigantinus and R. vagabundus, and commercial blackberry extracts.
Results showed “quantitative differences” in the composition of polyphenols in the extract.
The extracts were then subjected to conditions similar to those experienced in the gastrointestinal tract in order to produce metabolites, which were then tested on human brain cells.
While no effects were observed for the commercial blackberry extracts, the wild berry extracts were associated with a decrease in ROS levels, and activation of caspases.
“These effects protected neuronal cells against oxidative injury, one of the most important features of neurodegeneration,” wrote the researchers.
“It has been already described for some isolated phytochemicals that beneficial effects could be achieved through neurohormesis pathways, such as stimulating the vitagene system, the production of antioxidant enzymes, protein chaperons and other proteins that help cells to withstand stress.
“Therefore, these molecular targets should be a goal for future studies into the neuroprotection mediated by digested metabolites from wild blackberries.”
Source: European Journal of Nutrition
Published online qheqd of print, doi: 10.1007/s00394-012-0307-7
“Neuroprotective effects of digested polyphenols from wild blackberry species”
Authors: L. Tavares, I. Figueira, G.J. McDougall, H.L.A. Vieira, D. Stewart, P.M. Alves, R.B. Ferreira, C.N. Santos