I was researching several extracts listed in a commercial brand mix that comprises Ginkgo, phosphatidylserine, ***********, etc. The 1st herb listed though was Cat's Claw (Uncaria Tormentosa), You can read the impressive effects of this constituents of this herb at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6365538/.
The first two sentences in the Abstract says it all (you have to selectively read the whole article, for the evidence and findings supporting the claim):
Brain aging and Alzheimer’s disease both demonstrate the accumulation of beta-amyloid protein containing “plaques” and tau protein containing “tangles” that contribute to accelerated memory loss and cognitive decline.
In the present investigation we identified a specific plant extract and its constituents as a potential alternative natural solution for preventing and reducing both brain “plaques and tangles”.
The upper maximum dose (from mices' data) should be (conjecture): 50 mg/kg/day following 90-days of treatment. A safe estimate should be 1/5 of that, 10 mg/kg/day, which for a 100 kg person gives 1 gram / day, in agreement of the suggested dose per bulksupplements (500 mg one or twice a day).
My 5-star rating is based only on the above research; once I use the product, I will update this review.