Alzheimer’s disease represents one of the main neurological disorders in the aging population. This type of cognitive dysfunction  afflicts more than 4.5 million Americans, according to the Alzheimer’s Association. Dementia is one of the symptoms of this condition, which is characterized by the formation of protein deposits (amyloid plaques) and tangled bundles of fibers (neurofibrillary tangles) composed of misplaced proteins in the brain. As neurons are destroyed, the amount of neurotransmitters is significantly diminished, affecting the ability of the brain cells to communicate. The most affected neurotransmitter is acetylcholine; the newest class of drugs for Alzheimer’s disease aims to enhance the secretion of, or prolong the life of, acetylcholine in the brain. Enter the Strawberry Tree !

The Strawberry tree (Arbutus unedo L., Family: Ericeae ) is a small shrub growing in temperate climates and dislikes frost. In the UK it is found in places on the west coast of Scotland for example, but is prevalent throughout Europe.

The fruit contains a number of polyphenols, generally with antioxidant properties such as gallic acid, tannins, vitamin C, vitamin E, carotenoids and anthocyannins.

One study compared the anthocyanin levels in strawberry and raspberry (Rubus idaeus) to find that raspberries potentially have a stronger neuroprotective effect which needs further exploration (Fortelezas et al., 2010). Ellagitannins, a group of prominent antioxidant polyphenols in the strawberry tree fruit may be responsible for the beneficial effects in (McDonald and White, 1994; Shukitt et al., 2007).

Oxidative stress caused by the presence of the Aβ peptide is implicated in the pathogenesis of Alzheimers Disease (Papolla et al., 1998). The anti-oxidative effect of extracts of the strawberry tree was studied using a specialised cell type, PC12. Hydrogen peroxide (H₂O₂) was used to induce neurotoxicity in these PC12 cells and their viability or health was monitored using the lactate dehydrogenese (LDH) assay. Hydrogen peroxide treatment caused a loss of cell viability with a simultaneous increase in the release of LDH into the medium. Pre-treatment with an anthocyanin rich strawberry tree extract demonstrated better cell viability in PC12 cells that had been damaged by H₂O₂ (Heo and Lee, 2005).

Strawberry tree extract could attenuate undesirable behavioural changes caused by 56 Fe irradiation. High doses of irradiation in rats generated deficits in memory and spatial learning. Supplementation of strawberry tree extract for 8 weeks in the rat’s diet improved their spatial learning and memory. Most interestingly, a strawberry tree fruit diet showed improvement in a variety of hippocampal-dependent behaviours.

References

Fortalezas S, Tavares, L., Pimpão, R., Tyagi, M., Pontes, V., Alves, P., McDougall, G., Stewart, D., Ferreira R, Santos C (2010) Antioxidant properties and neuroprotective capacity of strawberry tree fruit (Arbutus unedo). Nutrients 2 pp. 214–229

Heo, H.J., Lee, C.Y. (2005) Strawberry and its anthocyanins reduce oxidative stress-induced apoptosis in PC12 cells. J Agric. Food Chem. 53 pp. 1984–1989

McDonald, R.J., White, N.M. (1994) Parallel information processing in the water maze: evidence for independent memory systems involving dorsal striatum and hippocampus. Behav. Neural. Biol. 61 pp. 260–270

Pappolla, M.A., Chyan, Y.J., Omar, R.A., Hsiao, K., Perry, G., Smith, M.A., Bozner, P (1998) Evidence of oxidative stress and in vivo neurotoxicity of beta-amyloid in a transgenic mouse model of Alzheimer’s disease—a chronic oxidative paradigm for testing antioxidant therapies in vivo. Am. J. Pathol. 152  pp. 871–877

Shukitt-Hale, B., Carey, A.N., Jenkins, D., Rabin, B.M., Joseph, J.A. (2007) Beneficial effects of fruit extracts on neuronal function and behavior in a rodent model of accelerated aging. Neurobiol. Aging 28 pp. 1187–1194