Not that I am aware of. I will ask our chief scientist.

Here is his response:

Hello Daniel

D-ribose, a 5-carbon (pentose) sugar, is a building block for ATP and for RNA. It is not a vitamin, since the body can produce it. As a dietary supplement it has benefited skeletal muscle and heart function, per a limited number of trials, but without any breakthrough results. The effective daily dose for muscle benefit is in gram amounts, from about 15 gm/day up to 30 gm/day or even 60 gm/day. It has been known to trigger hypoglycemic episodes.

I haven’t found any trials with D-ribose for brain function. There are implications from a couple early animal studies that D-ribose could be neuroprotective. However a recent study with mice found that a daily oral D-ribose dose of 3.75 g/kg/day for 6 months impaired learning and memory (per two maze tests).[Wu15] These mice also displayed anxiety-type behavior. The researchers found abnormal tau and amyloid deposition in the brain, especially in the hippocampus, and this damage was so bad that they seriously suggested D-ribose could be used to create an “Alzheimer’s model” in mice.

When I convert the daily dose that was found toxic to the mice into a human equivalent, using calculations endorsed by the FDA,[Sharma09] I come up with a human dose of 21.3 gm/day for a 70-kg (just 154-lb) human. This intake is well within the dosage range currently being recommended for humans. Further, since toxicity was clearly evident in the mice at this dose FDA would want to impose an additional lowering dose factor of at least 10 for safety, resulting in a “safe” human daily intake of no higher than 2.1 gm/day for a mere 154-lb human. This dose is likely too low to generate muscle, cardiac, or brain benefits.

Perhaps d-ribose advocates will challenge this recent mouse study though such advocates are few and far between—Stephen Sinatra may be one of those few. I don’t see any obvious flaws in the study’s methodology, and (unfortunately) now that it is in the peer-reviewed literature it will serve as a major disincentive against further research with d-ribose for the brain, due to legal/liability considerations. I doubt there was much promise of D-ribose for brain support in any case.