Here is an abstract which implicates peroxynitrites in the hyperphosphorylation and nitration of tau proteins. http://www.ncbi.nlm.nih.gov/pubmed/16816118 

Peroxynitrites have been linked either directly or indirectly to almost all aspects of Alzheimer's disease.  This again is why peroxynirtite scavengers have been effective in multiple animal studies, case studies, and clinical trials in Alzheimer's disease. 

You have asked some good questions and I will try to answer them one by one.

First, statins, as far as I understand are not antioxidants.  They limit g protein activation http://www.ncbi.nlm.nih.gov/pmc/articles/PMC209420/ which may be of some limited preventive help for some individuals and they may increase high density lipids which may be of particularly help to those with the APOE4 gene http://www.ncbi.nlm.nih.gov/pubmed/16973905 before the disease has started, but they appear to be of no use once a person has Alzheimer's disease.  The results from the studies regarding statins are just about what I expected.

Alpha tocopherol (the most commonly used form of Vitamin E) is not a peroxynitrite scavenger, but gamma tocopherol and probably gamma tocotrienols are.  With studies on Vitamin E and Alzheimer's disease (and other diseases) it is important to know what form of vitamin E is being used.  http://www.lef.org/Vitamins-Supplements/Item00559/Gamma-E-Tocopherol-Tocotrienols.html 

Ginkgo biloba is not a peroxynitrite scavenger.   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3035570/ 

It does not appear to be useful for the treatment of Alzheimer's disease.

Folate and Vitamin B12 can be peroxynitrite scavengers (but apparently not Vitamin B6), but whether the levels necessary to achieve this scavenging ability are possible in Alzheimer's patients has not be determined.  As you correctly not Folate, Vitamin B12, and Vitamin B6 can potentially lower homocysteine levels which is a major factor in peroxynitrite formation once the disease progresses, although even if they lowered homocysteine levels substantially, they likely would not reverse much if any of the damage done by peroxynitrites (unless given in very high doses which may not be safe).

Omega 3-fatty acids inhibit the formation of peroxynitrites (which helps explain their potential use in delaying the onset of the disease), but I have not found evidence yet that Omega 3-fatty acids are peroxynitrite scavenger.

So a number of the compounds you mention are not peroxynitrite scavengers, and as you note just because something is a peroxynitrite scavenger does not mean that it will reach the brain in sufficient quantities to reverse the disease.

Unfortunately, I do not have access to the types of compounds being used in various clinical trials using antioxidants in the treatment of Alzheimer's disease.  A number of them are ongoing.  The most promising one to date appears to be

the Souvenir trials.http://www.emaxhealth.com/1275/medical-food-souvenaid-helps-memory-mild-alzheimers 

Although inflammation is involved, oxidation, nitration, and calcium influx are the hallmarks of Alzheimer's disease.  All are the products of peroxynitrite and its derivatives. My contention is that if you find an effective peroxynitrite scavenger you have a chance to at least partially reverse the disease.

I should backtrack a bit: statins can be considered antioxidants in the sense they inhibit the activation of g proteins that can lead to peroxynitrite formation.

With the onset of Alzheimer's disease g protein-coupled receptors become oxidated by peroxynitrites and the main cause of peroxynitrite formation becomes high levels of homocysteine.  Statins become useless at this point (I am not sure even how useful they are before this point).

Here are some of the factors that directly or indirectly activate g proteins receptors prior to Alzheimer's disease: stress, estrogen, aluminium fluoride, and sodium fluoride.

http://www.fluoride-journal.com/98-31-2/31291-95.htm 

Heteriotremic G proteins activate phospholipase C beta which in turns activates Protein Kinase C which produces superoxide anions (via NADPH oxidase) and inducible nitric oxide (via Nuclear factor kappa b) which in turn combine to produce peroxynitrites.  The first part of this cascade leads to the formation of amyloid plaques.  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC43811/ 

The other enzyme which initiates the same cascade is phospholipase C gamma.

Factors which may increase phospholipase C gamma activation (via the platelet derived growth factor receptor) may include glucose, angiotensin II (a risk factor for high blood pressure), and various viruses and bacteria. 

Phospholipase C gamma and beta convert phosphatidylinostiol 4,5 biphosphate into inostiol 1,4,5 triphosphate.  The PI3 kinase converts phosphatidylinositol 4,5 biphosphate into phosphatidylinositol 3,4,5 triphosphate.  Inhibitors of this pathway increase the risk for Alzheimer's disease.  In order of highest to lowest inhibition this include presenilin gene mutations http://www.nature.com/emboj/journal/v23/n13/full/7600251a.html , the APOE4 gene http://www.ncbi.nlm.nih.gov/pubmed/16973905 and bishphosphonate osteoporosis drugs, such as Fosamax.

xhttp://www.ncbi.nlm.nih.gov/pubmed/16100524 

Finally,high levels of myo-inositol put a person at higher risk for Alzheimer's disease.  http://www.ncbi.nlm.nih.gov/pubmed/12366626 Myo-inositol which is a precursor to phosphatidylinositol 4,5 biphosphate increase due to high glucose levels, high blood pressure (caused by high sodium levels), or by Down syndrome (because individuals with Down syndrome carry an extra chromosome with the sodium/myo-inositol co-transporter).  http://www.ncbi.nlm.nih.gov/pubmed/10588400 

Ironically, estrogen may lower myo-inositol levels which may explain why early estrogen replacement therapy may be a possible method to prevent Alzheimer's disease whereas late estrogen replacement therapy may increase the risk for the disease.

Phenolic compounds and fish oil help impede the platelet derived growth factor activation of phospholipase C gamma. 

Impede peroxynitrite formation and you prevent or delay the onset of Alzheimer's disease.  Successfully scavenge peroxynitrites late and you not only stop the progression of the disease, you partially reverse it.

The export of zinc by phospholipase C and its later entombment in amyloid plaques contributes to the high levels of homocysteine in Alzheimer's disease.  This may limit the ability of Vitamin B12, Vitamin B6, and folate to lower homocysteine levels.  You cannot draw the conclusion that oxidation is unimportant to Alzheimer's disease because some antioxidants appear to be ineffective in the treatment of Alzheimer's disease.  Many other factors are at work, including the limited bioavailability and lowered uptake of some antioxidants. 

Let me refocus the discussion on a particular group of antioxidants: phenolic compounds.  Phenolic compounds (and polyunsaturated fats such as Omega 3-fatty acids) can potentially be used to delay the onset  http://www.ncbi.nlm.nih.gov/pubmed/16266772 

http://www.uab.es/servlet/Satellite/latest-news/news-detail/polyphenols-and-polyunsaturated-fatty-acids-boost-the-birth-of-new-neurons-1096476786473.html?noticiaid=1258978649304 

and treat Alzheimer's disease.

Phenolic compounds (and polyunsaturated fats) delay the onset of Alzheimer's disease by inhibiting the platelet derived growth factor receptor activation of phospholipase C and by inhibiting the formation of superoxide anions (via NADPH oxidase ) and inducible nitric oxide (via nuclear factor kappa b).

Phenolic compounds can probably be used to treat Alzheimer's disease because they:

Inhibit the formation of superoxide anions and inducible nitric oxide which combine to form peroxynitrites.

Scavenge peroxynitrites 

Partially reverse the peroxynitrite oxidation of g protein-coupled receptors involved in short-term memory, smell, sleep, mood, social recognition, and alertness.

Partially reverse the oxidation of choline, glucose, and glutamate transport systems.

Partially reverse the oxidation of the enzyme choline acetyltransferase.

Inhibit and partially reverse the nitration of tau proteins.  This would allow tau proteins to be reconstituted to come closer to normal neurotransmission and would allow for some degradation of amyloid plaques. http://www.cell.com/neuron/abstract/S0896-6273(11)00595-2 

Chelate zinc and copper out of amyloid plaques.

Lower the influx of calcium into neurons and the release of glutamate, thus limiting cell death.

Contribute to the production of brain derived growth factor which promotes neurogenesis in the hippocampus.

Eugenol, a methoxyphenol, accomplishes many if not all of these tasks:

http://www.sciencedirect.com/science/article/pii/S0969806X05002549 

http://www.springerlink.com/content/530075238uqk7525/ 

http://www.sciencedirect.com/science/article/pii/S0014299909007857 

http://www.ncbi.nlm.nih.gov/pubmed/15941312 

http://www.ingentaconnect.com/content/ben/cbc/2006/00000002/00000001/art00005 

My guess is that the most effective antioxidant interventions in Alzheimer's disease are going to include phenolic compounds contained in various fruits, vegetables, spices, and essential oils.

Actually, I didn't ask any questions.  What I did do was make a request which you have completely ignored, so let me repeat it.

You made a flat statement that peroxynitrite scavengers "have been effective in multiple animal studies, case studies, and clinical trials in Alzheimer's disease".

Please provide links to the published results of the "multiple clinical trials" which showed that peroxynitrite scavengers are effective in treating Alzheimer's patients.

Your implied question is why have not various antioxidants appeared successful in the treatment of Alzheimer's disease.  I tried to answer that question.  I didn't say that peroxynitrite scavengers have been effective in multiple clinical trials of Alzheimer's disease (we have already gone over the three clinical trials in which peroxynitrite scavenging essential oils were found by researchers to have a positive impact in cognitive function in Alzheimer's disease).  I said peroxynitrite scavengers have been effective in multiple animal studies, clinical trials, and case studies of Alzheimer's studies (for a review of most of these animal trials, clinical trials, and case studies one can go to the thread on aromatherapy).  What I will do here is post (in some cases repost) the animal studies (which I know you don't like), on peroxynitrite scavengers and Alzheimer's disease (although not all of these compounds are identified as peroxynitrite scavengers, they are).

 http://www.sciencedirect.com/science/article/pii/S0166432807001313 

http://www.ncbi.nlm.nih.gov/pubmed/20605227 

http://www.nature.com/npp/journal/v32/n11/full/1301377a.html 

http://www.jbc.org/content/286/7/4991.abstract 

http://www.greenpharmacy.info/article.asp?issn=0973-8258;year=2009;volume=3;issue=1;spage=6;epage=15;aulast=Raghavendra 

http://www.ncbi.nlm.nih.gov/pubmed/11513637 

http://informahealthcare.com/doi/abs/10.3109/13880209.2010.541924 

http://www.ncbi.nlm.nih.gov/pubmed/21905282 

http://onlinelibrary.wiley.com/doi/10.1111/j.1755-5949.2011.00237.x/abstract?systemMessage=Wiley+Online+Library+will+be+disrupted+4+Feb+from+10-12+GMT+for+monthly+maintenance 

Here is a very thorough article reviewing the antioxidant capacity of various essential oils.

http://onlinelibrary.wiley.com/doi/10.1002/ffj.1961/abstract 

It's worth clicking on the PDF to read the full article.

You are smart JAB and this is not that difficult.  We have covered the multiple damaging effects of peroxynitrites in Alzheimer's disease, we have discussed how compounds that donate hydrogen atoms and electrons scavenge peroxynitrites, we have discussed how peroxynitrite scavenger reverse some critical aspects of the disease (including the nitration of proteins, the oxidation of transport systems, and the oxidation of a variety of receptors), we have discussed how peroxynitrite scavengers have protected and ameliorated against cognitive decline in multiple animal models of Alzheimer's disease, we have discussed nursing home studies in which the use of aromatherapy led to significant improvements in Alzheimer's patients, we have discussed three small scale clinical trials in which according to the researchers, the use of aromatherapy led to significant improvements in cognitive function in all participants.  When something works time and again, you have to think it is attacking a key element of the disease. 

http://www.cryonet.org/cgi-bin/dsp.cgi?msg=32230 

http://www.cryonet.org/cgi-bin/dsp.cgi?msg=32233 

I will post further evidence as it becomes available.  I am not willing to wait until 2025 to find a cure for Alzheimer's disease, when a number of effective treatments already exist. 

I did not imply anything.  You made a flat statement for which there is no support in the scientific literature of which I am aware.  I asked you for that support.  You didn't provide it the first time I requested it, and I reiterated my request.  That was:

You made a flat statement that peroxynitrite scavengers "have been effective in multiple animal studies, case studies, and clinical trials in Alzheimer's disease".

(That is a verbatim quote from your post.)

Then I asked you to please provide links to the published results of the "multiple clinical trials" which showed that peroxynitrite scavengers are effective in treating Alzheimer's patients. 
 

If I understand you correctly this time, the only "clinical trial" evidence you have to offer are the three tiny, highly questionable studies on aromatherapy, which (a) say nothing whatsoever about the underlying mechanism being peroxynitrite scavenging, and more importantly (b) have been tossed out as being too problematic to consider being evidence of aromatherapy efficacy.  And they have been tossed out by multiple panels of experts tasked with reviewing the scientific literature for evidence that aromatherapy is of benefit to Alzheimer's patients.

For example, the most recent Cochrane database review, which evaluated case reports and clinical trials that had anything to do with aromatherapy and any aspect of treating dementia patients -- including affecting their cognitive function -- concluded that there was only one publication of sufficient caliber to be used in their analysis.  All of the others were discarded because the quality of the studies was so poor.   

 The single study which was of sufficiently good quality to be analyzed in the review was on the topical application of an oil in a lotion, not inhalation.  The reviewers noted there were "several methodological difficulties with this study."  And they stated, quite clearly, that this study "is insufficient evidence for the efficacy of aroma therapy for dementia." 

The Alzheimer's Association changed the name of this forum to "Clinical Trials" to emphasize the importance of large-scale clinical trial data to confirm that both efficacy and safety have been demonstrated in Alzheimer's patients, rather than relying on preclinical data.

Preclinical data, such as animal model (and cell and tissue culture data, which are even less reliable as being directly relevant) experiments, may not have anything whatsoever to do with what actually happens in a human being. 

And for anyone who doubts that statement ... how many clinical trials on candidate Alzheimer's treatments have been successful?

I am smart enough to recognize the fact that every time I ask you to provide support for one of your sweeping generalizations, you either ignore me or respond with a bunch of red herrings.

And I'll betcha that many of our other members are smart enough to recognize that fact, too.

Just for the record ...  Alpha-tocopherol was the vitamin E used in the large -- and unsuccessful -- clinical trial.  One would think that scientists who plan clinical trials would pay attention to which of the compounds that fall under the umbrella of "vitamin E" would be the most likely to be effective. 

Maybe they don't like to rely on an ad for a nutritional supplement as their source of information. 

A tiny handful of the many papers on this subject:

http://www.ajcn.org/content/74/6/714.full
"In vitro mechanistic studies established that under physiologically relevant conditions, peroxyl radicals or peroxynitrite mainly oxidizes α-tocopherol to 8a-hydroxy-α-tocopherone, which is then hydrolyzed to α-tocopherol quinone (α-TQ).  ...We observed that the yield of 5-Nγ-T generated during liposomal peroxidation initiated by peroxynitrite or 3-morpholinosydnonimine was independent of the presence of α-tocopherol, suggesting that γ-tocopherol may complement α-tocopherol in scavenging membrane-soluble RNOS (47). However, this conclusion was later questioned by Goss et al (50), who found that 5-Nγ-T could only be detected after α-tocopherol had been almost completely consumed.  ...Whether nitration of γ-tocopherol is a physiologically relevant process and occurs even in the presence of α-tocopherol can only be determined by in vivo experiments in which adequate analytic methods are used."

Please note that ref #47 is apparently the "112" paper cited in the nutritional supplement ad.

http://www.ncbi.nlm.nih.gov/pubmed/14994345
"alpha-Tocopherol (the most potent biological lipid antioxidant) may have a unique role in protecting mitochondrial membranes from oxidative stress. The two antioxidant nutrients alpha-tocopherol and ascorbate (which interact with each other and glutathione) may be intimately involved in protecting mitochondria in situations in which excessive release of superoxide and nitric oxide occurs under normal and/or pathological conditions."

http://www.ncbi.nlm.nih.gov/pubmed/9446836
"The fast and selective oxidation of alpha-tocopherol by peroxynitrite suggests that vitamin E may play an important role in preventing membrane oxidation induced by peroxynitrite."

http://www.ncbi.nlm.nih.gov/pubmed/8759030
"alpha-Tocopherol and ascorbate in synaptosomes were oxidized very rapidly by peroxynitrite."

I won't argue with you over the studies you provided on alpha-tocopherol, except to note that not all researchers have reached the same conclusion.   http://lpi.oregonstate.edu/ss03/vitamine.html.

You correctly quoted me, but you did not correctly intrepret me.  I said peroxynitrite scavengers have been effective in multiple animal studies, case studies, and clinical trials of Alzheimer's disease, I didn't say that peroxynitrite scavengers have been effective in multiple clinical trials of Alzheimer's disease.  It is a nuanced but important difference.  I know you hate animals models, but in every one a peroxynitrite scavenger either protected against or ameliorated cognitive decline of an Alzheimer-like disease.  Read carefully the conclusions that the scientists who did these studies reached.

At least four essential oils have been identified as peroxynitrite scavengers: bay laurel, Cinnamomum zeylanicum (true cinnamon), mountain savory, and oregano (I use all of these essential oils with my mother, except mountain savory which I am going to begin using).  For this information, see the Miguel link in the post on the animal studies.  If you wish me to compare the chemical composition of these four oils with the ones used in the clinical trials I can do so (any essential oil that contains methoxyphenols, such as eugnol, carvacrol, thymol and geraniol are likely peorxynitrite scavengers).

The review I cited was from 2002 was before the three clinical trials with essential oils.  The update you cited was from 2008--after the Akhondzadeh trials but before the Jimbo trial.  From the abstract, it is impossible to tell if the Akhondzadeh trial was excluded or not.  More importantly, the conclusion from both reviews was "the analysis of this one small trial showed a significant effect in favour of aroma therapy on measures of agitation and neuropsychiatric symptoms.  More large-scale randomized controls are needed before firm conclusions can be reached about the effectiveness of aroma therapy." Unfortunately, the next trial was barely largely, used much of the same methodology (apparently again the use of massage and an essential oil cream) and produced different results.  You cannot reach firm conclusions based on either trial, nor can it be ascertained from these trials whether a combination of essential oils using inhalation would have been more effective.  All that is available now are the case studies from the nursing care facilities (which again I know you don't like), in which the use of anti-psychotic drugs was dramatically reduced after the introduction of aromatherapy. 

So we have come to a standstill for now.  I have provided you with all the scientific studies, reviews, animal studies, case studies, and clinical trials I have regarding the role of peroxynitrites and peroxynitrite scavengers (including several essential oils) in Alzheimer's disease.  When more evidence becomes available, I will post it.