You might want to look into melatonin. Lots of research behind it and seems to have protective value too.

1: Behav Brain Funct. 2006 May 4;2(1):15.

Melatonin in Alzheimer's disease and other neurodegenerative disorders.

Srinivasan V, Pandi-Perumal S, Cardinali D, Poeggeler B, Hardeland R.

Johann Friedrich Blumenbach Institute of Zoology and Anthropology, University of
Goettingen, Berliner Str, 28, D-37073 Goettingen, Germany. rhardel@gwdg.de.

ABSTRACT : Increased oxidative stress and mitochondrial dysfunction have been
identified as common pathophysiological phenomena associated with
neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's
disease (PD) and Huntington's disease (HD). As the age-related decline in the
production of melatonin may contribute to increased levels of oxidative stress
in the elderly, the role of this neuroprotective agent is attracting increasing
attention. Melatonin has multiple actions as a regulator of antioxidant and
prooxidant enzymes, radical scavenger and antagonist of mitochondrial radical
formation. The ability of melatonin and its kynuramine metabolites to interact
directly with the electron transport chain by increasing the electron flow and
reducing electron leakage are unique features by which melatonin is able to
increase the survival of neurons under enhanced oxidative stress. Moreover,
antifibrillogenic actions have been demonstrated in vitro, also in the presence
of profibrillogenic apoE4 or apoE3, and in vivo, in a transgenic mouse model.
Amyloid-beta toxicity is antagonized by melatonin and one of its kynuramine
metabolites. Cytoskeletal disorganization and protein hyperphosphorylation, as
induced in several cell-line models, have been attenuated by melatonin, effects
comprising stress kinase downregulation and extending to neurotrophin
expression. Various experimental models of AD, PD and HD indicate the usefulness
of melatonin in antagonizing disease progression and/or mitigating some of the
symptoms. Melatonin secretion has been found to be altered in AD and PD.
Attempts to compensate for age- and disease-dependent melatonin deficiency have
shown that administration of this compound can improve sleep efficiency in AD
and PD and, to some extent, cognitive function in AD patients. Exogenous
melatonin has also been reported to alleviate behavioral symptoms such as
sundowning. Taken together, these findings suggest that melatonin, its analogues
and kynuric metabolites may have potential value in prevention and treatment of
AD and other neurodegenerative disorders.

PMID: 16674804 [PubMed - as supplied by publisher]